Cleavage And Polyadenylation Specificity Factor: An RNA-binding protein that recognizes the AAUAAA RNA SEQUENCE at the 3' end of MRNA. It contains four subunits of 30, 73, 100 and 160 kDa molecular size and combines with CLEAVAGE STIMULATION FACTOR to form a stable complex with mRNA that directs the 3' cleavage and polyadenylation reaction.mRNA Cleavage and Polyadenylation Factors: Factors that are involved in directing the cleavage and POLYADENYLATION of the of MESSENGER RNA near the site of the RNA 3' POLYADENYLATION SIGNALS.Polyadenylation: The addition of a tail of polyadenylic acid (POLY A) to the 3' end of mRNA (RNA, MESSENGER). Polyadenylation involves recognizing the processing site signal, (AAUAAA), and cleaving of the mRNA to create a 3' OH terminal end to which poly A polymerase (POLYNUCLEOTIDE ADENYLYLTRANSFERASE) adds 60-200 adenylate residues. The 3' end processing of some messenger RNAs, such as histone mRNA, is carried out by a different process that does not include the addition of poly A as described here.Cleavage Stimulation Factor: A RNA-binding protein that stimulates the cleavage of the 3' end of MRNA near the POLYADENYLATION site. It is a heterotrimer of 55-, 64- and 77-kDa subunits and combines with CLEAVAGE STIMULATION FACTOR to form a stable complex with mRNA that directs the 3' cleavage and polyadenylation reaction.Polynucleotide Adenylyltransferase: An enzyme that catalyzes the synthesis of polyadenylic acid from ATP. May be due to the action of RNA polymerase (EC 18.104.22.168) or polynucleotide adenylyltransferase (EC 22.214.171.124). EC 126.96.36.199.RNA 3' End Processing: The steps that generate the 3' ends of mature RNA molecules. For most mRNAs (RNA, MESSENGER), 3' end processing referred to as POLYADENYLATION includes the addition of POLY A.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.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.Poly A: A group of adenine ribonucleotides in which the phosphate residues of each adenine ribonucleotide act as bridges in forming diester linkages between the ribose moieties.RNA-Binding Proteins: Proteins that bind to RNA molecules. Included here are RIBONUCLEOPROTEINS and other proteins whose function is to bind specifically to 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.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.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.RNA 3' Polyadenylation Signals: Sequences found near the 3' end of MESSENGER RNA that direct the cleavage and addition of multiple ADENINE NUCLEOTIDES to the 3' end of mRNA.Base Sequence: The sequence of PURINES and PYRIMIDINES in nucleic acids and polynucleotides. It is also called nucleotide sequence.Substrate Specificity: A characteristic feature of enzyme activity in relation to the kind of substrate on which the enzyme or catalytic molecule reacts.Ribulose-Bisphosphate Carboxylase: A carboxy-lyase that plays a key role in photosynthetic carbon assimilation in the CALVIN-BENSON CYCLE by catalyzing the formation of 3-phosphoglycerate from ribulose 1,5-biphosphate and CARBON DIOXIDE. It can also utilize OXYGEN as a substrate to catalyze the synthesis of 2-phosphoglycolate and 3-phosphoglycerate in a process referred to as photorespiration.