Introns: Sequences of DNA in the genes that are located between the EXONS. They are transcribed along with the exons but are removed from the primary gene transcript by RNA SPLICING to leave mature RNA. Some introns code for separate genes.RNA Splicing: The ultimate exclusion of nonsense sequences or intervening sequences (introns) before the final RNA transcript is sent to the cytoplasm.Base Sequence: The sequence of PURINES and PYRIMIDINES in nucleic acids and polynucleotides. It is also called nucleotide sequence.Exons: The parts of a transcript of a split GENE remaining after the INTRONS are removed. They are spliced together to become a MESSENGER RNA or other functional RNA.Molecular Sequence Data: Descriptions of specific amino acid, carbohydrate, or nucleotide sequences which have appeared in the published literature and/or are deposited in and maintained by databanks such as GENBANK, European Molecular Biology Laboratory (EMBL), National Biomedical Research Foundation (NBRF), or other sequence repositories.Spliceosomes: Organelles in which the splicing and excision reactions that remove introns from precursor messenger RNA molecules occur. One component of a spliceosome is five small nuclear RNA molecules (U1, U2, U4, U5, U6) that, working in conjunction with proteins, help to fold pieces of RNA into the right shapes and later splice them into the message.RNA Splice Sites: Nucleotide sequences located at the ends of EXONS and recognized in pre-messenger RNA by SPLICEOSOMES. They are joined during the RNA SPLICING reaction, forming the junctions between exons.RNA Precursors: RNA transcripts of the DNA that are in some unfinished stage of post-transcriptional processing (RNA PROCESSING, POST-TRANSCRIPTIONAL) required for function. RNA precursors may undergo several steps of RNA SPLICING during which the phosphodiester bonds at exon-intron boundaries are cleaved and the introns are excised. Consequently a new bond is formed between the ends of the exons. Resulting mature RNAs can then be used; for example, mature mRNA (RNA, MESSENGER) is used as a template for protein production.Evolution, Molecular: The process of cumulative change at the level of DNA; RNA; and PROTEINS, over successive generations.Amino Acid Sequence: The order of amino acids as they occur in a polypeptide chain. This is referred to as the primary structure of proteins. It is of fundamental importance in determining PROTEIN CONFORMATION.Phylogeny: The relationships of groups of organisms as reflected by their genetic makeup.Cloning, Molecular: The insertion of recombinant DNA molecules from prokaryotic and/or eukaryotic sources into a replicating vehicle, such as a plasmid or virus vector, and the introduction of the resultant hybrid molecules into recipient cells without altering the viability of those cells.Nucleic Acid Conformation: The spatial arrangement of the atoms of a nucleic acid or polynucleotide that results in its characteristic 3-dimensional shape.Alternative Splicing: A process whereby multiple RNA transcripts are generated from a single gene. Alternative splicing involves the splicing together of other possible sets of EXONS during the processing of some, but not all, transcripts of the gene. Thus a particular exon may be connected to any one of several alternative exons to form a mature RNA. The alternative forms of mature MESSENGER RNA produce PROTEIN ISOFORMS in which one part of the isoforms is common while the other parts are different.Genes: A category of nucleic acid sequences that function as units of heredity and which code for the basic instructions for the development, reproduction, and maintenance of organisms.Sequence Homology, Nucleic Acid: The sequential correspondence of nucleotides in one nucleic acid molecule with those of another nucleic acid molecule. Sequence homology is an indication of the genetic relatedness of different organisms and gene function.Sequence Alignment: The arrangement of two or more amino acid or base sequences from an organism or organisms in such a way as to align areas of the sequences sharing common properties. The degree of relatedness or homology between the sequences is predicted computationally or statistically based on weights assigned to the elements aligned between the sequences. This in turn can serve as a potential indicator of the genetic relatedness between the organisms.RNA, Messenger: RNA sequences that serve as templates for protein synthesis. Bacterial mRNAs are generally primary transcripts in that they do not require post-transcriptional processing. Eukaryotic mRNA is synthesized in the nucleus and must be exported to the cytoplasm for translation. Most eukaryotic mRNAs have a sequence of polyadenylic acid at the 3' end, referred to as the poly(A) tail. The function of this tail is not known for certain, but it may play a role in the export of mature mRNA from the nucleus as well as in helping stabilize some mRNA molecules by retarding their degradation in the cytoplasm.RNA, Small Nuclear: Short chains of RNA (100-300 nucleotides long) that are abundant in the nucleus and usually complexed with proteins in snRNPs (RIBONUCLEOPROTEINS, SMALL NUCLEAR). Many function in the processing of messenger RNA precursors. Others, the snoRNAs (RNA, SMALL NUCLEOLAR), are involved with the processing of ribosomal RNA precursors.Sequence Analysis, DNA: A multistage process that includes cloning, physical mapping, subcloning, determination of the DNA SEQUENCE, and information analysis.Conserved Sequence: A sequence of amino acids in a polypeptide or of nucleotides in DNA or RNA that is similar across multiple species. A known set of conserved sequences is represented by a CONSENSUS SEQUENCE. AMINO ACID MOTIFS are often composed of conserved sequences.RNA, Catalytic: RNA that has catalytic activity. The catalytic RNA sequence folds to form a complex surface that can function as an enzyme in reactions with itself and other molecules. It may function even in the absence of protein. There are numerous examples of RNA species that are acted upon by catalytic RNA, however the scope of this enzyme class is not limited to a particular type of substrate.Euglena gracilis: A species of fresh-water, flagellated EUKARYOTES in the phylum EUGLENIDA.RNA, Fungal: Ribonucleic acid in fungi having regulatory and catalytic roles as well as involvement in protein synthesis.Transcription, Genetic: The biosynthesis of RNA carried out on a template of DNA. The biosynthesis of DNA from an RNA template is called REVERSE TRANSCRIPTION.Restriction Mapping: Use of restriction endonucleases to analyze and generate a physical map of genomes, genes, or other segments of DNA.Sequence Homology, Amino Acid: The degree of similarity between sequences of amino acids. This information is useful for the analyzing genetic relatedness of proteins and species.DNA: A deoxyribonucleotide polymer that is the primary genetic material of all cells. Eukaryotic and prokaryotic organisms normally contain DNA in a double-stranded state, yet several important biological processes transiently involve single-stranded regions. DNA, which consists of a polysugar-phosphate backbone possessing projections of purines (adenine and guanine) and pyrimidines (thymine and cytosine), forms a double helix that is held together by hydrogen bonds between these purines and pyrimidines (adenine to thymine and guanine to cytosine).Open Reading Frames: A sequence of successive nucleotide triplets that are read as CODONS specifying AMINO ACIDS and begin with an INITIATOR CODON and end with a stop codon (CODON, TERMINATOR).Biological Evolution: The process of cumulative change over successive generations through which organisms acquire their distinguishing morphological and physiological characteristics.Models, Genetic: Theoretical representations that simulate the behavior or activity of genetic processes or phenomena. They include the use of mathematical equations, computers, and other electronic equipment.DNA, Complementary: Single-stranded complementary DNA synthesized from an RNA template by the action of RNA-dependent DNA polymerase. cDNA (i.e., complementary DNA, not circular DNA, not C-DNA) is used in a variety of molecular cloning experiments as well as serving as a specific hybridization probe.Trans-Splicing: The joining of RNA from two different genes. One type of trans-splicing is the "spliced leader" type (primarily found in protozoans such as trypanosomes and in lower invertebrates such as nematodes) which results in the addition of a capped, noncoding, spliced leader sequence to the 5' end of mRNAs. Another type of trans-splicing is the "discontinuous group II introns" type (found in plant/algal chloroplasts and plant mitochondria) which results in the joining of two independently transcribed coding sequences. Both are mechanistically similar to conventional nuclear pre-mRNA cis-splicing. Mammalian cells are also capable of trans-splicing.Genes, Fungal: The functional hereditary units of FUNGI.Chromosome Mapping: Any method used for determining the location of and relative distances between genes on a chromosome.Genome: The genetic complement of an organism, including all of its GENES, as represented in its DNA, or in some cases, its RNA.Genes, Plant: The functional hereditary units of PLANTS.Genomic Library: A form of GENE LIBRARY containing the complete DNA sequences present in the genome of a given organism. It contrasts with a cDNA library which contains only sequences utilized in protein coding (lacking introns).Species Specificity: The restriction of a characteristic behavior, anatomical structure or physical system, such as immune response; metabolic response, or gene or gene variant to the members of one species. It refers to that property which differentiates one species from another but it is also used for phylogenetic levels higher or lower than the species.Polymerase Chain Reaction: In vitro method for producing large amounts of specific DNA or RNA fragments of defined length and sequence from small amounts of short oligonucleotide flanking sequences (primers). The essential steps include thermal denaturation of the double-stranded target molecules, annealing of the primers to their complementary sequences, and extension of the annealed primers by enzymatic synthesis with DNA polymerase. The reaction is efficient, specific, and extremely sensitive. Uses for the reaction include disease diagnosis, detection of difficult-to-isolate pathogens, mutation analysis, genetic testing, DNA sequencing, and analyzing evolutionary relationships.Chlorophyta: A phylum of photosynthetic EUKARYOTA bearing double membrane-bound plastids containing chlorophyll a and b. They comprise the classical green algae, and represent over 7000 species that live in a variety of primarily aquatic habitats. Only about ten percent are marine species, most live in freshwater.Blotting, Southern: A method (first developed by E.M. Southern) for detection of DNA that has been electrophoretically separated and immobilized by blotting on nitrocellulose or other type of paper or nylon membrane followed by hybridization with labeled NUCLEIC ACID PROBES.Cryptophyta: A class of EUKARYOTA (traditionally algae), characterized by biflagellated cells and found in both freshwater and marine environments. Pigmentation varies but only one CHLOROPLAST is present. Unique structures include a nucleomorph and ejectosomes.Base Composition: The relative amounts of the PURINES and PYRIMIDINES in a nucleic acid.RNA: A polynucleotide consisting essentially of chains with a repeating backbone of phosphate and ribose units to which nitrogenous bases are attached. RNA is unique among biological macromolecules in that it can encode genetic information, serve as an abundant structural component of cells, and also possesses catalytic activity. (Rieger et al., Glossary of Genetics: Classical and Molecular, 5th ed)Ribonucleoproteins, Small Nuclear: Highly conserved nuclear RNA-protein complexes that function in RNA processing in the nucleus, including pre-mRNA splicing and pre-mRNA 3'-end processing in the nucleoplasm, and pre-rRNA processing in the nucleolus (see RIBONUCLEOPROTEINS, SMALL NUCLEOLAR).Ascomycota: A phylum of fungi which have cross-walls or septa in the mycelium. The perfect state is characterized by the formation of a saclike cell (ascus) containing ascospores. Most pathogenic fungi with a known perfect state belong to this phylum.RNA, Ribosomal, Self-Splicing: Components of ribosomal RNA that undergo auto-catalyzed molecular rearrangements of their RNA sequence.Ribonucleoprotein, U2 Small Nuclear: A nuclear RNA-protein complex that plays a role in RNA processing. In the nucleoplasm, the U2 snRNP along with other small nuclear ribonucleoproteins (U1, U4-U6, and U5) assemble into SPLICEOSOMES that remove introns from pre-mRNA by splicing. The U2 snRNA forms base pairs with conserved sequence motifs at the branch point, which associates with a heat- and RNAase-sensitive factor in an early step of splicing.Retroelements: Elements that are transcribed into RNA, reverse-transcribed into DNA and then inserted into a new site in the genome. Long terminal repeats (LTRs) similar to those from retroviruses are contained in retrotransposons and retrovirus-like elements. Retroposons, such as LONG INTERSPERSED NUCLEOTIDE ELEMENTS and SHORT INTERSPERSED NUCLEOTIDE ELEMENTS do not contain LTRs.DNA, Fungal: Deoxyribonucleic acid that makes up the genetic material of fungi.RNA, Ribosomal: The most abundant form of RNA. Together with proteins, it forms the ribosomes, playing a structural role and also a role in ribosomal binding of mRNA and tRNAs. Individual chains are conventionally designated by their sedimentation coefficients. In eukaryotes, four large chains exist, synthesized in the nucleolus and constituting about 50% of the ribosome. (Dorland, 28th ed)Tetrahymena: A genus of ciliate protozoa commonly used in genetic, cytological, and other research.Pseudogenes: Genes bearing close resemblance to known genes at different loci, but rendered non-functional by additions or deletions in structure that prevent normal transcription or translation. When lacking introns and containing a poly-A segment near the downstream end (as a result of reverse copying from processed nuclear RNA into double-stranded DNA), they are called processed genes.Promoter Regions, Genetic: DNA sequences which are recognized (directly or indirectly) and bound by a DNA-dependent RNA polymerase during the initiation of transcription. Highly conserved sequences within the promoter include the Pribnow box in bacteria and the TATA BOX in eukaryotes.Untranslated Regions: The parts of the messenger RNA sequence that do not code for product, i.e. the 5' UNTRANSLATED REGIONS and 3' UNTRANSLATED REGIONS.Mutation: Any detectable and heritable change in the genetic material that causes a change in the GENOTYPE and which is transmitted to daughter cells and to succeeding generations.Fishes, PoisonousNucleic Acid Precursors: Use for nucleic acid precursors in general or for which there is no specific heading.Naegleria: A free-living soil amoeba pathogenic to humans and animals. It occurs also in water and sewage. The most commonly found species in man is NAEGLERIA FOWLERI which is the pathogen for primary amebic meningoencephalitis in primates.Multigene Family: A set of genes descended by duplication and variation from some ancestral gene. Such genes may be clustered together on the same chromosome or dispersed on different chromosomes. Examples of multigene families include those that encode the hemoglobins, immunoglobulins, histocompatibility antigens, actins, tubulins, keratins, collagens, heat shock proteins, salivary glue proteins, chorion proteins, cuticle proteins, yolk proteins, and phaseolins, as well as histones, ribosomal RNA, and transfer RNA genes. The latter three are examples of reiterated genes, where hundreds of identical genes are present in a tandem array. (King & Stanfield, A Dictionary of Genetics, 4th ed)DNA Restriction Enzymes: Enzymes that are part of the restriction-modification systems. They catalyze the endonucleolytic cleavage of DNA sequences which lack the species-specific methylation pattern in the host cell's DNA. Cleavage yields random or specific double-stranded fragments with terminal 5'-phosphates. The function of restriction enzymes is to destroy any foreign DNA that invades the host cell. Most have been studied in bacterial systems, but a few have been found in eukaryotic organisms. They are also used as tools for the systematic dissection and mapping of chromosomes, in the determination of base sequences of DNAs, and have made it possible to splice and recombine genes from one organism into the genome of another. EC 3.21.1.DNA, Intergenic: Any of the DNA in between gene-coding DNA, including untranslated regions, 5' and 3' flanking regions, INTRONS, non-functional pseudogenes, and non-functional repetitive sequences. This DNA may or may not encode regulatory functions.Vertebrates: Animals having a vertebral column, members of the phylum Chordata, subphylum Craniata comprising mammals, birds, reptiles, amphibians, and fishes.Repetitive Sequences, Nucleic Acid: Sequences of DNA or RNA that occur in multiple copies. There are several types: INTERSPERSED REPETITIVE SEQUENCES are copies of transposable elements (DNA TRANSPOSABLE ELEMENTS or RETROELEMENTS) dispersed throughout the genome. TERMINAL REPEAT SEQUENCES flank both ends of another sequence, for example, the long terminal repeats (LTRs) on RETROVIRUSES. Variations may be direct repeats, those occurring in the same direction, or inverted repeats, those opposite to each other in direction. TANDEM REPEAT SEQUENCES are copies which lie adjacent to each other, direct or inverted (INVERTED REPEAT SEQUENCES).DNA, Mitochondrial: Double-stranded DNA of MITOCHONDRIA. In eukaryotes, the mitochondrial GENOME is circular and codes for ribosomal RNAs, transfer RNAs, and about 10 proteins.DNA Primers: Short sequences (generally about 10 base pairs) of DNA that are complementary to sequences of messenger RNA and allow reverse transcriptases to start copying the adjacent sequences of mRNA. Primers are used extensively in genetic and molecular biology techniques.DNA Transposable Elements: Discrete segments of DNA which can excise and reintegrate to another site in the genome. Most are inactive, i.e., have not been found to exist outside the integrated state. DNA transposable elements include bacterial IS (insertion sequence) elements, Tn elements, the maize controlling elements Ac and Ds, Drosophila P, gypsy, and pogo elements, the human Tigger elements and the Tc and mariner elements which are found throughout the animal kingdom.Databases, Nucleic Acid: Databases containing information about NUCLEIC ACIDS such as BASE SEQUENCE; SNPS; NUCLEIC ACID CONFORMATION; and other properties. Information about the DNA fragments kept in a GENE LIBRARY or GENOMIC LIBRARY is often maintained in DNA databases.Euglenida: A phylum of unicellular flagellates of ancient eukaryotic lineage with unclear taxonomy. They lack a CELL WALL but are covered by a proteinaceous flexible coat, the pellicle, that allows the cell to change shape. Historically some authorities considered them to be an order of protozoa and others classed them as ALGAE (some members have CHLOROPLASTS and some don't).Eukaryotic Cells: Cells of the higher organisms, containing a true nucleus bounded by a nuclear membrane.RNA, Small Nucleolar: Small nuclear RNAs that are involved in the processing of pre-ribosomal RNA in the nucleolus. Box C/D containing snoRNAs (U14, U15, U16, U20, U21 and U24-U63) direct site-specific methylation of various ribose moieties. Box H/ACA containing snoRNAs (E2, E3, U19, U23, and U64-U72) direct the conversion of specific uridines to pseudouridine. Site-specific cleavages resulting in the mature ribosomal RNAs are directed by snoRNAs U3, U8, U14, U22 and the snoRNA components of RNase MRP and RNase P.RNA, Plant: Ribonucleic acid in plants having regulatory and catalytic roles as well as involvement in protein synthesis.Chloroplasts: Plant cell inclusion bodies that contain the photosynthetic pigment CHLOROPHYLL, which is associated with the membrane of THYLAKOIDS. Chloroplasts occur in cells of leaves and young stems of plants. They are also found in some forms of PHYTOPLANKTON such as HAPTOPHYTA; DINOFLAGELLATES; DIATOMS; and CRYPTOPHYTA.Codon: A set of three nucleotides in a protein coding sequence that specifies individual amino acids or a termination signal (CODON, TERMINATOR). Most codons are universal, but some organisms do not produce the transfer RNAs (RNA, TRANSFER) complementary to all codons. These codons are referred to as unassigned codons (CODONS, NONSENSE).DNA, Chloroplast: Deoxyribonucleic acid that makes up the genetic material of CHLOROPLASTS.Fungi: A kingdom of eukaryotic, heterotrophic organisms that live parasitically as saprobes, including MUSHROOMS; YEASTS; smuts, molds, etc. They reproduce either sexually or asexually, and have life cycles that range from simple to complex. Filamentous fungi, commonly known as molds, refer to those that grow as multicellular colonies.Plants: Multicellular, eukaryotic life forms of kingdom Plantae (sensu lato), comprising the VIRIDIPLANTAE; RHODOPHYTA; and GLAUCOPHYTA; all of which acquired chloroplasts by direct endosymbiosis of CYANOBACTERIA. They are characterized by a mainly photosynthetic mode of nutrition; essentially unlimited growth at localized regions of cell divisions (MERISTEMS); cellulose within cells providing rigidity; the absence of organs of locomotion; absence of nervous and sensory systems; and an alternation of haploid and diploid generations.5' Untranslated Regions: The sequence at the 5' end of the messenger RNA that does not code for product. This sequence contains the ribosome binding site and other transcription and translation regulating sequences.Saccharomyces cerevisiae: A species of the genus SACCHAROMYCES, family Saccharomycetaceae, order Saccharomycetales, known as "baker's" or "brewer's" yeast. The dried form is used as a dietary supplement.RNA Processing, Post-Transcriptional: Post-transcriptional biological modification of messenger, transfer, or ribosomal RNAs or their precursors. It includes cleavage, methylation, thiolation, isopentenylation, pseudouridine formation, conformational changes, and association with ribosomal protein.RNA-Binding Proteins: Proteins that bind to RNA molecules. Included here are RIBONUCLEOPROTEINS and other proteins whose function is to bind specifically to RNA.Endonucleases: Enzymes that catalyze the hydrolysis of the internal bonds and thereby the formation of polynucleotides or oligonucleotides from ribo- or deoxyribonucleotide chains. EC 3.1.-.Hepatophyta: A plant division. They are simple plants that lack vascular tissue and possess rudimentary rootlike organs (rhizoids). Like MOSSES, liverworts have alternation of generations between haploid gamete-bearing forms (gametophytes) and diploid spore-bearing forms (sporophytes).Genes, Protozoan: The functional hereditary units of protozoa.Nucleic Acid Hybridization: Widely used technique which exploits the ability of complementary sequences in single-stranded DNAs or RNAs to pair with each other to form a double helix. Hybridization can take place between two complimentary DNA sequences, between a single-stranded DNA and a complementary RNA, or between two RNA sequences. The technique is used to detect and isolate specific sequences, measure homology, or define other characteristics of one or both strands. (Kendrew, Encyclopedia of Molecular Biology, 1994, p503)Drosophila melanogaster: A species of fruit fly much used in genetics because of the large size of its chromosomes.Expressed Sequence Tags: Partial cDNA (DNA, COMPLEMENTARY) sequences that are unique to the cDNAs from which they were derived.RNA, Archaeal: Ribonucleic acid in archaea having regulatory and catalytic roles as well as involvement in protein synthesis.Arabidopsis: A plant genus of the family BRASSICACEAE that contains ARABIDOPSIS PROTEINS and MADS DOMAIN PROTEINS. The species A. thaliana is used for experiments in classical plant genetics as well as molecular genetic studies in plant physiology, biochemistry, and development.Inteins: The internal fragments of precursor proteins (INternal proTEINS) that are autocatalytically removed by PROTEIN SPLICING. The flanking fragments (EXTEINS) are ligated forming mature proteins. The nucleic acid sequences coding for inteins are considered to be MOBILE GENETIC ELEMENTS. Inteins are composed of self-splicing domains and an endonuclease domain which plays a role in the spread of the intein's genomic sequence. Mini-inteins are composed of the self-splicing domains only.Basidiomycota: A phylum of fungi that produce their sexual spores (basidiospores) on the outside of the basidium. It includes forms commonly known as mushrooms, boletes, puffballs, earthstars, stinkhorns, bird's-nest fungi, jelly fungi, bracket or shelf fungi, and rust and smut fungi.Ribosomal Proteins: Proteins found in ribosomes. They are believed to have a catalytic function in reconstituting biologically active ribosomal subunits.Computational Biology: A field of biology concerned with the development of techniques for the collection and manipulation of biological data, and the use of such data to make biological discoveries or predictions. This field encompasses all computational methods and theories for solving biological problems including manipulation of models and datasets.Thermoproteales: An order of CRENARCHAEOTA comprised of rod, disc, or spherical shaped, nonseptate, anaerobic, extreme thermophiles and found in solfataric hot waters, mud holes, and superheated submarine environments.Cytochromes b: Cytochromes of the b group that have alpha-band absorption of 563-564 nm. They occur as subunits in MITOCHONDRIAL ELECTRON TRANSPORT COMPLEX III.Genome, Mitochondrial: The genetic complement of MITOCHONDRIA as represented in their DNA.Gene Library: A large collection of DNA fragments cloned (CLONING, MOLECULAR) from a given organism, tissue, organ, or cell type. It may contain complete genomic sequences (GENOMIC LIBRARY) or complementary DNA sequences, the latter being formed from messenger RNA and lacking intron sequences.Genetic Variation: Genotypic differences observed among individuals in a population.Blotting, Northern: Detection of RNA that has been electrophoretically separated and immobilized by blotting on nitrocellulose or other type of paper or nylon membrane followed by hybridization with labeled NUCLEIC ACID PROBES.Genome, Plant: The genetic complement of a plant (PLANTS) as represented in its DNA.DNA, Plant: Deoxyribonucleic acid that makes up the genetic material of plants.Consensus Sequence: A theoretical representative nucleotide or amino acid sequence in which each nucleotide or amino acid is the one which occurs most frequently at that site in the different sequences which occur in nature. The phrase also refers to an actual sequence which approximates the theoretical consensus. A known CONSERVED SEQUENCE set is represented by a consensus sequence. Commonly observed supersecondary protein structures (AMINO ACID MOTIFS) are often formed by conserved sequences.Euglena: A genus of EUKARYOTES, in the phylum EUGLENIDA, found mostly in stagnant water. Characteristics include a pellicle usually marked by spiral or longitudinal striations.
Intron: right|thumbnail|270px|Representation of intron and [[exons within a simple gene containing a single intron.]]Symmetry element: A symmetry element is a point of reference about which symmetry operations can take place. In particular, symmetry elements can be centers of inversion, axes of rotation and mirror planes.Alternative splicing: Alternative splicing is a regulated process during gene expression that results in a single gene coding for multiple proteins. In this process, particular exons of a gene may be included within or excluded from the final, processed messenger RNA (mRNA) produced from that gene.Coles PhillipsU11 spliceosomal RNAMolecular evolution: Molecular evolution is a change in the sequence composition of cellular molecules such as DNA, RNA, and proteins across generations. The field of molecular evolution uses principles of evolutionary biology and population genetics to explain patterns in these changes.Protein primary structure: The primary structure of a peptide or protein is the linear sequence of its amino acid structural units, and partly comprises its overall biomolecular structure. By convention, the primary structure of a protein is reported starting from the amino-terminal (N) end to the carboxyl-terminal (C) end.Branching order of bacterial phyla (Gupta, 2001): There are several models of the Branching order of bacterial phyla, one of these was proposed in 2001 by Gupta based on conserved indels or protein, termed "protein signatures", an alternative approach to molecular phylogeny. Some problematic exceptions and conflicts are present to these conserved indels, however, they are in agreement with several groupings of classes and phyla.Ligation-independent cloning: Ligation-independent cloning (LIC) is a form of molecular cloning that is able to be performed without the use of restriction endonucleases or DNA ligase. This allows genes that have restriction sites to be cloned without worry of chopping up the insert.Nucleic acid structure: Nucleic acid structure refers to the structure of nucleic acids such as DNA and RNA. Chemically speaking, DNA and RNA are very similar.CS-BLASTMature messenger RNA: Mature messenger RNA, often abbreviated as mature mRNA is a eukaryotic RNA transcript that has been spliced and processed and is ready for translation in the course of protein synthesis. Unlike the eukaryotic RNA immediately after transcription known as precursor messenger RNA, it consists exclusively of exons, with all introns removed.U6 spliceosomal RNADNA sequencer: A DNA sequencer is a scientific instrument used to automate the DNA sequencing process. Given a sample of DNA, a DNA sequencer is used to determine the order of the four bases: G (guanine), C (cytosine), A (adenine) and T (thymine).Hairpin ribozymeGroup III intron: Group III intron is a class of introns found in mRNA genes of chloroplasts in euglenid protists. They have a conventional group II-type dVI with a bulged adenosine, a streamlined dI, no dII-dV, and a relaxed splice site consensus.Eukaryotic transcription: Eukaryotic transcription is the elaborate process that eukaryotic cells use to copy genetic information stored in DNA into units of RNA replica. Gene transcription occurs in both eukaryotic and prokaryotic cells.DNA condensation: DNA condensation refers to the process of compacting DNA molecules in vitro or in vivo. Mechanistic details of DNA packing are essential for its functioning in the process of gene regulation in living systems.Open reading frame: In molecular genetics, an open reading frame (ORF) is the part of a reading frame that has the potential to code for a protein or peptide. An ORF is a continuous stretch of codons that do not contain a stop codon (usually UAA, UAG or UGA).Trans-splicing: Trans-splicing is a special form of RNA processing in eukaryotes where exons from two different primary RNA transcripts are joined end to end and ligated.Chromosome regionsList of sequenced eukaryotic genomesThermal cyclerHaematococcus pluvialis: Haematococcus pluvialis is a freshwater species of Chlorophyta from the family Haematococcaceae. This species is well known for its high content of the strong antioxidant astaxanthin, which is important in aquaculture, and cosmetics.Nucleomorph: Nucleomorphs are small, vestigial eukaryotic nuclei found between the inner and outer pairs of membranes in certain plastids. They are thought to be vestiges of primitive red and green algal nuclei that engulfed a prokaryote (plastid).YjdF RNA motifLasiodiplodia: Lasiodiplodia is a genus of fungi in the family Botryosphaeriaceae. There are 21 species.Ty5 retrotransposon: The Ty5 is a type of retrotransposon native to the Saccharomyces cerevisiae organism.MT-RNR2: Mitochondrially encoded 16S RNA (often abbreviated as 16S) is a mitochondrial ribosomal RNA (rRNA) that in humans is encoded by the MT-RNR2 gene. The MT-RNR2 gene also encodes the Humanin polypeptide that has been the target of Alzheimer's disease research.Vg1 ribozyme: The Vg1 ribozyme is a manganese dependent RNA enzyme or ribozyme which is the smallest ribozyme to be identified. It was identified in the 3' UTR of Xenopus Vg1 mRNA transcripts and mouse beta-actin mRNA.GC box: In molecular biology, a GC box is a distinct pattern of nucleotides found in the promoter region of some eukaryotic genes upstream of the TATA box and approximately 110 bases upstream from the transcription initiation site. It has a consensus sequence GGGCGG which is position dependent and orientation independent.Silent mutation: Silent mutations are mutations in DNA that do not significantly alter the phenotype of the organism in which they occur. Silent mutations can occur in non-coding regions (outside of genes or within introns), or they may occur within exons.Synanceia: Synanceia is a genus of fish of the family Synanceiidae, the stonefishes, whose members are venomous, dangerous, and even fatal to humans. It is one of the most venomous fish currently known in the world.Naegleria: Naegleria is a genus of protozoa. The genus was named after French zoologist Mathieu Naegler.ParaHox: The ParaHox gene cluster is an array of homeobox genes (involved in morphogenesis, the regulation of patterns of anatomical development) from the Gsx, Xlox (Pdx) and Cdx gene families.Restriction fragment: A restriction fragment is a DNA fragment resulting from the cutting of a DNA strand by a restriction enzyme (restriction endonucleases), a process called restriction. Each restriction enzyme is highly specific, recognising a particular short DNA sequence, or restriction site, and cutting both DNA strands at specific points within this site.Intergenic region: An Intergenic region (IGR) is a stretch of DNA sequences located between genes. Intergenic regions are a subset of Noncoding DNA.Direct repeat: Direct repeats are a type of genetic sequence that consists of two or more repeats of a specific sequence.Haplogroup L0 (mtDNA)Composite transposon: A composite transposon is similar in function to simple transposons and Insertion Sequence (IS) elements in that it has protein coding DNA segments flanked by inverted, repeated sequences that can be recognized by transposase enzymes. A composite transposon, however, is flanked by two separate IS elements which may or may not be exact replicas.Calkinsia: Calkinsia is a monotypic genus of alga comprising the single species Calkinsia aureus. It lives in low-oxygen seafloor environments.Pyrococcus C/D box small nucleolar RNALeucoplastCodon Adaptation Index: The Codon Adaptation Index (CAI) is the most widespread technique for analyzing Codon usage bias. As opposed to other measures of codon usage bias, such as the 'effective number of codons' (Nc), which measure deviation from a uniform bias (null hypothesis), CAI measures the deviation of a given protein coding gene sequence with respect to a reference set of genes.Marine fungi: Marine fungi are species of fungi that live in marine or estuarine environments. They are not a taxonomic group but share a common habitat.Zuotin: Z-DNA binding protein 1, also known as Zuotin, is a Saccharomyces cerevisiae yeast gene.RNA-binding protein database: The RNA-binding Proteins Database (RBPDB) is a biological database of RNA-binding protein specificities that includes experimental observations of RNA-binding sites. The experimental results included are both in vitro and in vivo from primary literature.Excision repair cross-complementing: Excision repair cross-complementing (ERCC) is a set of proteins which are involved in DNA repair.PerrottetineneIndy (gene): Indy, short for I'm not dead yet, is a gene of the model organism, the fruit fly Drosophila melanogaster. Mutant versions of this gene have doubled the average life span of fruit flies in at least one set of experiments, but this result has been subject to controversy.Sequence clustering: In bioinformatics, sequence clustering algorithms attempt to group biological sequences that are somehow related. The sequences can be either of genomic, "transcriptomic" (ESTs) or protein origin.GAI (Arabidopsis thaliana gene)Protein splicing: Protein splicing is an intramolecular reaction of a particular protein in which an internal protein segment (called an intein) is removed from a precursor protein with a ligation of C-terminal and N-terminal external proteins (called exteins) on both sides. The splicing junction of the precursor protein is mainly a cysteine or a serine, which are amino acids containing a nucleophilic side chain.Puccinia striiformis var. striiformis: Puccinia striiformis var. striiformis is a plant pathogen.RMF RNA motif: The rmf RNA motif is a conserved RNA structure that was originally detected using bioinformatics. rmf RNAs are consistently foundwithin species classified into the genus Pseudomonas, and is located potentially in the 5' untranslated regions (5' UTRs) of rmf genes.PSI Protein Classifier: PSI Protein Classifier is a program generalizing the results of both successive and independent iterations of the PSI-BLAST program. PSI Protein Classifier determines belonging of the found by PSI-BLAST proteins to the known families.Thermoproteales: In taxonomy, the Thermoproteales are an order of the Thermoprotei.See the NCBI webpage on Thermoproteales.NADH-QLibrary (biology): In molecular biology, a library is a collection of DNA fragments that is stored and propagated in a population of micro-organisms through the process of molecular cloning. There are different types of DNA libraries, including cDNA libraries (formed from reverse-transcribed RNA), genomic libraries (formed from genomic DNA) and randomized mutant libraries (formed by de novo gene synthesis where alternative nucleotides or codons are incorporated).Genetic variation: right|thumb
(1/9869) In vivo expression of the nucleolar group I intron-encoded I-dirI homing endonuclease involves the removal of a spliceosomal intron.
The Didymium iridis DiSSU1 intron is located in the nuclear SSU rDNA and has an unusual twin-ribozyme organization. One of the ribozymes (DiGIR2) catalyses intron excision and exon ligation. The other ribozyme (DiGIR1), which along with the endonuclease-encoding I-DirI open reading frame (ORF) is inserted in DiGIR2, carries out hydrolysis at internal processing sites (IPS1 and IPS2) located at its 3' end. Examination of the in vivo expression of DiSSU1 shows that after excision, DiSSU1 is matured further into the I-DirI mRNA by internal DiGIR1-catalysed cleavage upstream of the ORF 5' end, as well as truncation and polyadenylation downstream of the ORF 3' end. A spliceosomal intron, the first to be reported within a group I intron and the rDNA, is removed before the I-DirI mRNA associates with the polysomes. Taken together, our results imply that DiSSU1 uses a unique combination of intron-supplied ribozyme activity and adaptation to the general RNA polymerase II pathway of mRNA expression to allow a protein to be produced from the RNA polymerase I-transcribed rDNA. (+info)
(2/9869) Tight binding of the 5' exon to domain I of a group II self-splicing intron requires completion of the intron active site.
Group II self-splicing requires the 5' exon to form base pairs with two stretches of intronic sequence (EBS1 and EBS2) which also bind the DNA target during retrotransposition of the intron. We have used dimethyl sulfate modification of bases to obtain footprints of the 5' exon on intron Pl.LSU/2 from the mitochondrion of the alga Pylaiella littoralis, as well as on truncated intron derivatives. Aside from the EBS sites, which are part of the same subdomain (ID) of ribozyme secondary structure, three distant adenines become either less or more sensitive to modification in the presence of the exon. Unexpectedly, one of these adenines in subdomain IC1 is footprinted only in the presence of the distal helix of domain V, which is involved in catalysis. While the loss of that footprint is accompanied by a 100-fold decrease in the affinity for the exon, both protection from modification and efficient binding can be restored by a separate domain V transcript, whose binding results in its own, concise footprint on domains I and III. Possible biological implications of the need for the group II active site to be complete in order to observe high-affinity binding of the 5' exon to domain I are discussed. (+info)
(3/9869) A premature termination codon interferes with the nuclear function of an exon splicing enhancer in an open reading frame-dependent manner.
Premature translation termination codon (PTC)-mediated effects on nuclear RNA processing have been shown to be associated with a number of human genetic diseases; however, how these PTCs mediate such effects in the nucleus is unclear. A PTC at nucleotide (nt) 2018 that lies adjacent to the 5' element of a bipartite exon splicing enhancer within the NS2-specific exon of minute virus of mice P4 promoter-generated pre-mRNA caused a decrease in the accumulated levels of P4-generated R2 mRNA relative to P4-generated R1 mRNA, although the total accumulated levels of P4 product remained the same. This effect was seen in nuclear RNA and was independent of RNA stability. The 5' and 3' elements of the bipartite NS2-specific exon enhancer are redundant in function, and when the 2018 PTC was combined with a deletion of the 3' enhancer element, the exon was skipped in the majority of the viral P4-generated product. Such exon skipping in response to a PTC, but not a missense mutation at nt 2018, could be suppressed by frame shift mutations in either exon of NS2 which reopened the NS2 open reading frame, as well as by improvement of the upstream intron 3' splice site. These results suggest that a PTC can interfere with the function of an exon splicing enhancer in an open reading frame-dependent manner and that the PTC is recognized in the nucleus. (+info)
(4/9869) Alterations in the conserved SL1 trans-spliced leader of Caenorhabditis elegans demonstrate flexibility in length and sequence requirements in vivo.
Approximately 70% of mRNAs in Caenorhabditis elegans are trans spliced to conserved 21- to 23-nucleotide leader RNAs. While the function of SL1, the major C. elegans trans-spliced leader, is unknown, SL1 RNA, which contains this leader, is essential for embryogenesis. Efforts to characterize in vivo requirements of the SL1 leader sequence have been severely constrained by the essential role of the corresponding DNA sequences in SL1 RNA transcription. We devised a heterologous expression system that circumvents this problem, making it possible to probe the length and sequence requirements of the SL1 leader without interfering with its transcription. We report that expression of SL1 from a U2 snRNA promoter rescues mutants lacking the SL1-encoding genes and that the essential embryonic function of SL1 is retained when approximately one-third of the leader sequence and/or the length of the leader is significantly altered. In contrast, although all mutant SL1 RNAs were well expressed, more severe alterations eliminate this essential embryonic function. The one non-rescuing mutant leader tested was never detected on messages, demonstrating that part of the leader sequence is essential for trans splicing in vivo. Thus, in spite of the high degree of SL1 sequence conservation, its length, primary sequence, and composition are not critical parameters of its essential embryonic function. However, particular nucleotides in the leader are essential for the in vivo function of the SL1 RNA, perhaps for its assembly into a functional snRNP or for the trans-splicing reaction. (+info)
(5/9869) Promoter and exon-intron structure of the protein kinase C gene from the marine sponge Geodia cydonium: evolutionary considerations and promoter activity.
We report the gene structure of a key signaling molecule from a marine sponge, Geodia cydonium. The selected gene, which codes for a classical protein kinase C (cPKC), comprises 13 exons and 12 introns; the introns are, in contrast to those found in cPKC from higher Metazoa, small in size ranging from 93 nt to 359 nt. The complete gene has a length of 4229 nt and contains exons which encode the characteristic putative regulatory and catalytic domains of metazoan cPKCs. While in the regulatory domain only one intron is in phase 0, in the catalytic domain most introns are phase 0 introns, suggesting that the latter only rarely undergo module duplication. The 5'-flanking sequence of the sponge cPKC gene contains a TATA-box like motif which is located 35-26 nt upstream from the start of the longest sequenced cDNA. This 5'-flanking sequence was analyzed for promoter activity. The longest fragment (538 nt) was able to drive the expression of luciferase in transient transfections of NIH 3T3 fibroblasts; the strong activity of the sponge promoter was found to be half the one displayed by the SV40 reference promoter. Deletion analysis demonstrates that the AP4 site and the GC box which is most adjacent to the TATA box are the crucial elements for maximal promoter activity. The activity of the promoter is not changed in 3T3 cells which are kept serum starved or in the presence of a phorbol ester. In conclusion, these data present the phylogenetically oldest cPKC gene which contains in the 5'-flanking region a promoter functional in the heterologous mammalian cell system. (+info)
(6/9869) Interleukin-18 binding protein: a novel modulator of the Th1 cytokine response.
An interleukin-18 binding protein (IL-18BP) was purified from urine by chromatography on IL-18 beads, sequenced, cloned, and expressed in COS7 cells. IL-18BP abolished IL-18 induction of interferon-gamma (IFNgamma), IL-8, and activation of NF-kappaB in vitro. Administration of IL-18BP to mice abrogated circulating IFNgamma following LPS. Thus, IL-18BP functions as an inhibitor of the early Th1 cytokine response. IL-18BP is constitutively expressed in the spleen, belongs to the immunoglobulin superfamily, and has limited homology to the IL-1 type II receptor. Its gene was localized on human chromosome 11q13, and no exon coding for a transmembrane domain was found in an 8.3 kb genomic sequence. Several Poxviruses encode putative proteins highly homologous to IL-18BP, suggesting that viral products may attenuate IL-18 and interfere with the cytotoxic T cell response. (+info)
(7/9869) The stability and fate of a spliced intron from vertebrate cells.
Introns constitute most of the length of typical pre-mRNAs in vertebrate cells. Thus, the turnover rate of introns may significantly influence the availability of ribonucleotides and splicing factors for further rounds of transcription and RNA splicing, respectively. Given the importance of intron turnover, it is surprising that there have been no reports on the half-life of introns from higher eukaryotic cells. Here, we determined the stability of IVS1Cbeta1, the first intron from the constant region of the mouse T-cell receptor-beta, (TCR-beta) gene. Using a tetracycline (tet)-regulated promoter, we demonstrate that spliced IVS1Cbeta1 and its pre-mRNA had half-lives of 6.0+/-1.4 min and 3.7+/-1.0 min, respectively. We also examined the half-lives of these transcripts by using actinomycin D (Act.D). Act.D significantly stabilized IVS1Cbeta1 and its pre-mRNA, suggesting that Act.D not only blocks transcription but exerts rapid and direct posttranscriptional effects in the nucleus. We observed that in vivo spliced IVS1Cbeta1 accumulated predominantly as lariat molecules that use a consensus branchpoint nucleotide. The accumulation of IVS1Cbeta1 as a lariat did not result from an intrinsic inability to be debranched, as it could be debranched in vitro, albeit somewhat less efficiently than an adenovirus intron. Subcellular-fractionation and sucrose-gradient analyses showed that most spliced IVS1Cbeta1 lariats cofractionated with pre-mRNA, but not always with mRNA in the nucleus. Some IVS1Cbeta1 also appeared to be selectively exported to the cytoplasm, whereas TCR-beta pre-mRNA remained in the nucleus. This study constitutes the first detailed analysis of the stability and fate of a spliced nuclear intron in vivo. (+info)
(8/9869) Genome-wide bioinformatic and molecular analysis of introns in Saccharomyces cerevisiae.
Introns have typically been discovered in an ad hoc fashion: introns are found as a gene is characterized for other reasons. As complete eukaryotic genome sequences become available, better methods for predicting RNA processing signals in raw sequence will be necessary in order to discover genes and predict their expression. Here we present a catalog of 228 yeast introns, arrived at through a combination of bioinformatic and molecular analysis. Introns annotated in the Saccharomyces Genome Database (SGD) were evaluated, questionable introns were removed after failing a test for splicing in vivo, and known introns absent from the SGD annotation were added. A novel branchpoint sequence, AAUUAAC, was identified within an annotated intron that lacks a six-of-seven match to the highly conserved branchpoint consensus UACUAAC. Analysis of the database corroborates many conclusions about pre-mRNA substrate requirements for splicing derived from experimental studies, but indicates that splicing in yeast may not be as rigidly determined by splice-site conservation as had previously been thought. Using this database and a molecular technique that directly displays the lariat intron products of spliced transcripts (intron display), we suggest that the current set of 228 introns is still not complete, and that additional intron-containing genes remain to be discovered in yeast. The database can be accessed at http://www.cse.ucsc.edu/research/compbi o/yeast_introns.html. (+info)
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