Apc4 Subunit, Anaphase-Promoting Complex-Cyclosome: A subunit of the anaphase-promoting complex whose primary function is to provide structural support for the catalytic and substrate-recognition modules of the complex. Apc4, along with Apc5, tethers the tetratricopeptide-coactivator binding subcomplex to the main structural subunit, Apc1.Apc1 Subunit, Anaphase-Promoting Complex-Cyclosome: The largest subunit of the anaphase-promoting complex. It acts primarily as a scaffold for the proper organization and arrangement of subunits. The C-terminal region of Apc1 contains a series of tandem amino acid repeats that are also seen in the 26S proteasome regulatory particle, and may assist with forming and stabilizing protein-protein interactions.Apc10 Subunit, Anaphase-Promoting Complex-Cyclosome: Apc10 is necessary for coactivator-dependent substrate recognition by the anaphase-promoting complex-cyclosome. It binds the Apc2 subunit, which is a part of the catalytic core, and interacts with coactivators Cdh1 or Cdc20 to recruit substrates to the complex.Apc5 Subunit, Anaphase-Promoting Complex-Cyclosome: A subunit of the anaphase-promoting complex whose primary function is to provide structural support for the catalytic and substrate-recognition modules of the complex. Apc5, along with Apc4, tethers the tetratricopeptide-coactivator binding subcomplex to the main structural subunit, Apc1.Apc2 Subunit, Anaphase-Promoting Complex-Cyclosome: Together with the Apc11 subunit, forms the catalytic core of the E3 ubiquitin ligase anaphase-promoting complex (APC-C). Its N-terminus has cullin domains which associate with the RING FINGER DOMAINS of Apc11. Apc2 also interacts with the E2 ubiquitin ligases involved in APC-C ubiquitination reactions.Apc11 Subunit, Anaphase-Promoting Complex-Cyclosome: Together with the Apc2 subunit, forms the catalytic core of the E3 ubiquitin ligase, anaphase-promoting complex-cyclosome. It has a RING H2 domain which interacts with the cullin domain of Apc2. Apc11 also interacts with the E2 ubiquitin ligases involved in APC-C ubiquitination reactions.Apc7 Subunit, Anaphase-Promoting Complex-Cyclosome: A highly conserved subunit of the anaphase-promoting complex (APC-C) containing multiple 34 amino acid tetratricopeptide repeats. These domains, also found in Apc3, Apc6, and Apc8, have been shown to mediate protein-protein interactions, suggesting that Apc7 may assist in coordinating the juxtaposition of the catalytic and substrate recognition module subunits relative to coactivators and APC-C inhibitors.Anaphase-Promoting Complex-Cyclosome: An E3 ubiquitin ligase primarily involved in regulation of the metaphase-to-anaphase transition during MITOSIS through ubiquitination of specific CELL CYCLE PROTEINS. Enzyme activity is tightly regulated through subunits and cofactors, which modulate activation, inhibition, and substrate specificity. The anaphase-promoting complex, or APC-C, is also involved in tissue differentiation in the PLACENTA, CRYSTALLINE LENS, and SKELETAL MUSCLE, and in regulation of postmitotic NEURONAL PLASTICITY and excitability.Apc8 Subunit, Anaphase-Promoting Complex-Cyclosome: A highly conserved subunit of the anaphase-promoting complex (APC-C) containing multiple 34-amino-acid tetratricopeptide repeats. These domains, also found in Apc3, Apc6, and Apc7, have been shown to mediate protein-protein interactions, suggesting that Apc8 may assist in coordinating the juxtaposition of the catalytic and substrate recognition module subunits relative to coactivators and APC-C inhibitors.Apc6 Subunit, Anaphase-Promoting Complex-Cyclosome: A highly conserved subunit of the anaphase-promoting complex (APC-C) containing multiple 34 amino acid tetratricopeptide repeats. These domains, also found in Apc3, Apc7, and Apc8, have been shown to mediate protein-protein interactions, suggesting that Apc6 may assist in coordinating the juxtaposition of the catalytic and substrate recognition module subunits relative to coactivators and APC-C inhibitors.Apc3 Subunit, Anaphase-Promoting Complex-Cyclosome: A highly evolutionarily conserved subunit of the anaphase-promoting complex (APC-C) containing multiple 34-amino-acid tetratricopeptide repeats. These domains, also found in Apc subunits 6, 7, and 8, have been shown to mediate protein-protein interactions, suggesting that Apc3 may assist in coordinating the juxtaposition of the catalytic and substrate recognition module subunits relative to co-activators and APC-C inhibitors.Ubiquitin-Protein Ligase Complexes: Complexes of enzymes that catalyze the covalent attachment of UBIQUITIN to other proteins by forming a peptide bond between the C-terminal GLYCINE of UBIQUITIN and the alpha-amino groups of LYSINE residues in the protein. The complexes play an important role in mediating the selective-degradation of short-lived and abnormal proteins. The complex of enzymes can be broken down into three components that involve activation of ubiquitin (UBIQUITIN-ACTIVATING ENZYMES), conjugation of ubiquitin to the ligase complex (UBIQUITIN-CONJUGATING ENZYMES), and ligation of ubiquitin to the substrate protein (UBIQUITIN-PROTEIN LIGASES).Cdc20 Proteins: Highly conserved proteins that specifically bind to and activate the anaphase-promoting complex-cyclosome, promoting ubiquitination and proteolysis of cell-cycle-regulatory proteins. Cdc20 is essential for anaphase-promoting complex activity, initiation of anaphase, and cyclin proteolysis during mitosis.Cdh1 Proteins: Cdh1 is an activator of the anaphase-promoting complex-cyclosome, and is involved in substrate recognition. It associates with the complex in late MITOSIS from anaphase through G1 to regulate activity of CYCLIN-DEPENDENT KINASES and to prevent premature DNA replication.Anaphase: The phase of cell nucleus division following METAPHASE, in which the CHROMATIDS separate and migrate to opposite poles of the spindle.Cell Cycle Proteins: Proteins that control the CELL DIVISION CYCLE. This family of proteins includes a wide variety of classes, including CYCLIN-DEPENDENT KINASES, mitogen-activated kinases, CYCLINS, and PHOSPHOPROTEIN PHOSPHATASES as well as their putative substrates such as chromatin-associated proteins, CYTOSKELETAL PROTEINS, and TRANSCRIPTION FACTORS.Mitosis: A type of CELL NUCLEUS division by means of which the two daughter nuclei normally receive identical complements of the number of CHROMOSOMES of the somatic cells of the species.Ligases: A class of enzymes that catalyze the formation of a bond between two substrate molecules, coupled with the hydrolysis of a pyrophosphate bond in ATP or a similar energy donor. (Dorland, 28th ed) EC 6.Securin: Securin is involved in the control of the metaphase-anaphase transition during MITOSIS. It promotes the onset of anaphase by blocking SEPARASE function and preventing proteolysis of cohesin and separation of sister CHROMATIDS. Overexpression of securin is associated with NEOPLASTIC CELL TRANSFORMATION and tumor formation.Cyclin B: A cyclin subtype that is transported into the CELL NUCLEUS at the end of the G2 PHASE. It stimulates the G2/M phase transition by activating CDC2 PROTEIN KINASE.Mad2 Proteins: Mad2 is a component of the spindle-assembly checkpoint apparatus. It binds to and inhibits the Cdc20 activator subunit of the anaphase-promoting complex, preventing the onset of anaphase until all chromosomes are properly aligned at the metaphase plate. Mad2 is required for proper microtubule capture at KINETOCHORES.Ubiquitin-Protein Ligases: A diverse class of enzymes that interact with UBIQUITIN-CONJUGATING ENZYMES and ubiquitination-specific protein substrates. Each member of this enzyme group has its own distinct specificity for a substrate and ubiquitin-conjugating enzyme. Ubiquitin-protein ligases exist as both monomeric proteins multiprotein complexes.Metaphase: The phase of cell nucleus division following PROMETAPHASE, in which the CHROMOSOMES line up across the equatorial plane of the SPINDLE APPARATUS prior to separation.Spindle Apparatus: A microtubule structure that forms during CELL DIVISION. It consists of two SPINDLE POLES, and sets of MICROTUBULES that may include the astral microtubules, the polar microtubules, and the kinetochore microtubules.F-Box Proteins: A family of proteins that share the F-BOX MOTIF and are involved in protein-protein interactions. They play an important role in process of protein ubiquition by associating with a variety of substrates and then associating into SCF UBIQUITIN LIGASE complexes. They are held in the ubiquitin-ligase complex via binding to SKP DOMAIN PROTEINS.Cyclin B1: A cyclin B subtype that colocalizes with MICROTUBULES during INTERPHASE and is transported into the CELL NUCLEUS at the end of the G2 PHASE.Ubiquitination: The act of ligating UBIQUITINS to PROTEINS to form ubiquitin-protein ligase complexes to label proteins for transport to the PROTEASOME ENDOPEPTIDASE COMPLEX where proteolysis occurs.Prometaphase: The phase of cell nucleus division following PROPHASE, when the breakdown of the NUCLEAR ENVELOPE occurs and the MITOTIC SPINDLE APPARATUS enters the nuclear region and attaches to the KINETOCHORES.M Phase Cell Cycle Checkpoints: The cellular signaling system that halts the progression of cells through MITOSIS or MEIOSIS if a defect that will affect CHROMOSOME SEGREGATION is detected.Cell Cycle: The complex series of phenomena, occurring between the end of one CELL DIVISION and the end of the next, by which cellular material is duplicated and then divided between two daughter cells. The cell cycle includes INTERPHASE, which includes G0 PHASE; G1 PHASE; S PHASE; and G2 PHASE, and CELL DIVISION PHASE.Cyclin A2: A widely-expressed cyclin A subtype that functions during the G1/S and G2/M transitions of the CELL CYCLE.Saccharomyces cerevisiae Proteins: Proteins obtained from the species SACCHAROMYCES CEREVISIAE. The function of specific proteins from this organism are the subject of intense scientific interest and have been used to derive basic understanding of the functioning similar proteins in higher eukaryotes.Ubiquitin: A highly conserved 76-amino acid peptide universally found in eukaryotic cells that functions as a marker for intracellular PROTEIN TRANSPORT and degradation. Ubiquitin becomes activated through a series of complicated steps and forms an isopeptide bond to lysine residues of specific proteins within the cell. These "ubiquitinated" proteins can be recognized and degraded by proteosomes or be transported to specific compartments within the cell.Ubiquitin-Conjugating Enzymes: A class of enzymes that form a thioester bond to UBIQUITIN with the assistance of UBIQUITIN-ACTIVATING ENZYMES. They transfer ubiquitin to the LYSINE of a substrate protein with the assistance of UBIQUITIN-PROTEIN LIGASES.CDC2 Protein Kinase: Phosphoprotein with protein kinase activity that functions in the G2/M phase transition of the CELL CYCLE. It is the catalytic subunit of the MATURATION-PROMOTING FACTOR and complexes with both CYCLIN A and CYCLIN B in mammalian cells. The maximal activity of cyclin-dependent kinase 1 is achieved when it is fully dephosphorylated.Separase: Separase is a caspase-like cysteine protease, which plays a central role in triggering ANAPHASE by cleaving the SCC1/RAD21 subunit of the cohesin complex. Cohesin holds the sister CHROMATIDS together during METAPHASE and its cleavage results in chromosome segregation.Meiosis: A type of CELL NUCLEUS division, occurring during maturation of the GERM CELLS. Two successive cell nucleus divisions following a single chromosome duplication (S PHASE) result in daughter cells with half the number of CHROMOSOMES as the parent cells.HeLa Cells: The first continuously cultured human malignant CELL LINE, derived from the cervical carcinoma of Henrietta Lacks. These cells are used for VIRUS CULTIVATION and antitumor drug screening assays.Schizosaccharomyces pombe Proteins: Proteins obtained from the species Schizosaccharomyces pombe. The function of specific proteins from this organism are the subject of intense scientific interest and have been used to derive basic understanding of the functioning similar proteins in higher eukaryotes.Cyclin A: A cyclin subtype that has specificity for CDC2 PROTEIN KINASE and CYCLIN-DEPENDENT KINASE 2. It plays a role in progression of the CELL CYCLE through G1/S and G2/M phase transitions.Chromosome Segregation: The orderly segregation of CHROMOSOMES during MEIOSIS or MITOSIS.CDC28 Protein Kinase, S cerevisiae: A protein kinase encoded by the Saccharomyces cerevisiae CDC28 gene and required for progression from the G1 PHASE to the S PHASE in the CELL CYCLE.SKP Cullin F-Box Protein Ligases: A subset of ubiquitin protein ligases that are formed by the association of a SKP DOMAIN PROTEIN, a CULLIN DOMAIN PROTEIN and a F-BOX DOMAIN PROTEIN.G1 Phase: The period of the CELL CYCLE preceding DNA REPLICATION in S PHASE. Subphases of G1 include "competence" (to respond to growth factors), G1a (entry into G1), G1b (progression), and G1c (assembly). Progression through the G1 subphases is effected by limiting growth factors, nutrients, or inhibitors.Schizosaccharomyces: A genus of ascomycetous fungi of the family Schizosaccharomycetaceae, order Schizosaccharomycetales.Proto-Oncogene Proteins c-mos: Cellular proteins encoded by the c-mos genes (GENES, MOS). They function in the cell cycle to maintain MATURATION PROMOTING FACTOR in the active state and have protein-serine/threonine kinase activity. Oncogenic transformation can take place when c-mos proteins are expressed at the wrong time.Fungal Proteins: Proteins found in any species of fungus.Geminin: Geminin inhibits DNA replication by preventing the incorporation of MCM complex into pre-replication complex. It is absent during G1 phase of the CELL CYCLE and accumulates through S, G2,and M phases. It is degraded at the metaphase-anaphase transition by the ANAPHASE-PROMOTING COMPLEX-CYCLOSOME.Ubiquitins: A family of proteins that are structurally-related to Ubiquitin. Ubiquitins and ubiquitin-like proteins participate in diverse cellular functions, such as protein degradation and HEAT-SHOCK RESPONSE, by conjugation to other proteins.Endoreduplication: A type of nuclear polyploidization in which multiple cycles of DNA REPLICATION occur in the absence of CELL DIVISION and result in a POLYPLOID CELL.Xenopus: An aquatic genus of the family, Pipidae, occurring in Africa and distinguished by having black horny claws on three inner hind toes.Chromatids: Either of the two longitudinally adjacent threads formed when a eukaryotic chromosome replicates prior to mitosis. The chromatids are held together at the centromere. Sister chromatids are derived from the same chromosome. (Singleton & Sainsbury, Dictionary of Microbiology and Molecular Biology, 2d ed)Protein-Serine-Threonine Kinases: A group of enzymes that catalyzes the phosphorylation of serine or threonine residues in proteins, with ATP or other nucleotides as phosphate donors.Tosylarginine Methyl Ester: Arginine derivative which is a substrate for many proteolytic enzymes. As a substrate for the esterase from the first component of complement, it inhibits the action of C(l) on C(4).Kinetochores: Large multiprotein complexes that bind the centromeres of the chromosomes to the microtubules of the mitotic spindle during metaphase in the cell cycle.Xenopus Proteins: Proteins obtained from various species of Xenopus. Included here are proteins from the African clawed frog (XENOPUS LAEVIS). Many of these proteins have been the subject of scientific investigations in the area of MORPHOGENESIS and development.Cyclin-Dependent Kinase Inhibitor Proteins: A group of cell cycle proteins that negatively regulate the activity of CYCLIN/CYCLIN-DEPENDENT KINASE complexes. They inhibit CELL CYCLE progression and help control CELL PROLIFERATION following GENOTOXIC STRESS as well as during CELL DIFFERENTIATION.Nuclear Proteins: Proteins found in the nucleus of a cell. Do not confuse with NUCLEOPROTEINS which are proteins conjugated with nucleic acids, that are not necessarily present in the nucleus.Protein Binding: The process in which substances, either endogenous or exogenous, bind to proteins, peptides, enzymes, protein precursors, or allied compounds. Specific protein-binding measures are often used as assays in diagnostic assessments.Nocodazole: Nocodazole is an antineoplastic agent which exerts its effect by depolymerizing microtubules.Protein Subunits: Single chains of amino acids that are the units of multimeric PROTEINS. Multimeric proteins can be composed of identical or non-identical subunits. One or more monomeric subunits may compose a protomer which itself is a subunit structure of a larger assembly.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.Proteolysis: Cleavage of proteins into smaller peptides or amino acids either by PROTEASES or non-enzymatically (e.g., Hydrolysis). It does not include Protein Processing, Post-Translational.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.Proteasome Endopeptidase Complex: A large multisubunit complex that plays an important role in the degradation of most of the cytosolic and nuclear proteins in eukaryotic cells. It contains a 700-kDa catalytic sub-complex and two 700-kDa regulatory sub-complexes. The complex digests ubiquitinated proteins and protein activated via ornithine decarboxylase antizyme.Prophase: The first phase of cell nucleus division, in which the CHROMOSOMES become visible, the CELL NUCLEUS starts to lose its identity, the SPINDLE APPARATUS appears, and the CENTRIOLES migrate toward opposite poles.S Phase: Phase of the CELL CYCLE following G1 and preceding G2 when the entire DNA content of the nucleus is replicated. It is achieved by bidirectional replication at multiple sites along each chromosome.Cytokinesis: The process by which the CYTOPLASM of a cell is divided.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.Genes, cdc: Genes that code for proteins that regulate the CELL DIVISION CYCLE. These genes form a regulatory network that culminates in the onset of MITOSIS by activating the p34cdc2 protein (PROTEIN P34CDC2).Amino Acid Motifs: Commonly observed structural components of proteins formed by simple combinations of adjacent secondary structures. A commonly observed structure may be composed of a CONSERVED SEQUENCE which can be represented by a CONSENSUS SEQUENCE.S-Phase Kinase-Associated Proteins: A family of structurally-related proteins that were originally identified by their ability to complex with cyclin proteins (CYCLINS). They share a common domain that binds specifically to F-BOX MOTIFS. They take part in SKP CULLIN F-BOX PROTEIN LIGASES, where they can bind to a variety of F-BOX PROTEINS.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.Calcium-Binding Proteins: Proteins to which calcium ions are bound. They can act as transport proteins, regulator proteins, or activator proteins. They typically contain EF HAND MOTIFS.Substrate Specificity: A characteristic feature of enzyme activity in relation to the kind of substrate on which the enzyme or catalytic molecule reacts.Oocytes: Female germ cells derived from OOGONIA and termed OOCYTES when they enter MEIOSIS. The primary oocytes begin meiosis but are arrested at the diplotene state until OVULATION at PUBERTY to give rise to haploid secondary oocytes or ova (OVUM).Aurora Kinases: A family of highly conserved serine-threonine kinases that are involved in the regulation of MITOSIS. They are involved in many aspects of cell division, including centrosome duplication, SPINDLE APPARATUS formation, chromosome alignment, attachment to the spindle, checkpoint activation, and CYTOKINESIS.Cell Extracts: Preparations of cell constituents or subcellular materials, isolates, or substances.G2 Phase: The period of the CELL CYCLE following DNA synthesis (S PHASE) and preceding M PHASE (cell division phase). The CHROMOSOMES are tetraploid in this point.Saccharomycetales: An order of fungi in the phylum Ascomycota that multiply by budding. They include the telomorphic ascomycetous yeasts which are found in a very wide range of habitats.RNA Interference: A gene silencing phenomenon whereby specific dsRNAs (RNA, DOUBLE-STRANDED) trigger the degradation of homologous mRNA (RNA, MESSENGER). The specific dsRNAs are processed into SMALL INTERFERING RNA (siRNA) which serves as a guide for cleavage of the homologous mRNA in the RNA-INDUCED SILENCING COMPLEX. DNA METHYLATION may also be triggered during this process.Cadherins: Calcium-dependent cell adhesion proteins. They are important in the formation of ADHERENS JUNCTIONS between cells. Cadherins are classified by their distinct immunological and tissue specificities, either by letters (E- for epithelial, N- for neural, and P- for placental cadherins) or by numbers (cadherin-12 or N-cadherin 2 for brain-cadherin). Cadherins promote cell adhesion via a homophilic mechanism as in the construction of tissues and of the whole animal body.Repressor Proteins: Proteins which maintain the transcriptional quiescence of specific GENES or OPERONS. Classical repressor proteins are DNA-binding proteins that are normally bound to the OPERATOR REGION of an operon, or the ENHANCER SEQUENCES of a gene until a signal occurs that causes their release.Meiotic Prophase I: The prophase of the first division of MEIOSIS (in which homologous CHROMOSOME SEGREGATION occurs). It is divided into five stages: leptonema, zygonema, PACHYNEMA, diplonema, and diakinesis.Phosphorylation: The introduction of a phosphoryl group into a compound through the formation of an ester bond between the compound and a phosphorus moiety.Polyubiquitin: An oligomer formed from the repetitive linking of the C-terminal glycine of one UBIQUITIN molecule via an isopeptide bond to a lysine residue on a second ubiquitin molecule. It is structurally distinct from UBIQUITIN C, which is a single protein containing a tandemly arrayed ubiquitin peptide sequence.Centrosome: The cell center, consisting of a pair of CENTRIOLES surrounded by a cloud of amorphous material called the pericentriolar region. During interphase, the centrosome nucleates microtubule outgrowth. The centrosome duplicates and, during mitosis, separates to form the two poles of the mitotic spindle (MITOTIC SPINDLE APPARATUS).Models, Biological: Theoretical representations that simulate the behavior or activity of biological processes or diseases. For disease models in living animals, DISEASE MODELS, ANIMAL is available. Biological models include the use of mathematical equations, computers, and other electronic equipment.Chicken anemia virus: The type species of GYROVIRUS, a small, non-enveloped DNA virus originally isolated from contaminated vaccines in Japan. It causes chicken infectious anemia and may possibly play a key role in hemorrhagic anemia syndrome, anemia dermatitis, and blue wing disease.Cyclin-Dependent Kinases: Protein kinases that control cell cycle progression in all eukaryotes and require physical association with CYCLINS to achieve full enzymatic activity. Cyclin-dependent kinases are regulated by phosphorylation and dephosphorylation events.beta-Transducin Repeat-Containing Proteins: A family of F-box domain proteins that contain sequences that are homologous to the beta subunit of transducin (BETA-TRANSDUCIN). They play an important role in the protein degradation pathway by becoming components of SKP CULLIN F-BOX PROTEIN LIGASES, which selectively act on a subset of proteins including beta-catenin and IkappaBbeta.Cullin Proteins: A family of structurally related proteins that were originally discovered for their role in cell-cycle regulation in CAENORHABDITIS ELEGANS. They play important roles in regulation of the CELL CYCLE and as components of UBIQUITIN-PROTEIN LIGASES.Protein Kinases: A family of enzymes that catalyze the conversion of ATP and a protein to ADP and a phosphoprotein.