Polynucleotide adenylyltransferase

polynucleotide adenylyltransferase
Identifiers
EC number	2.7.7.19
CAS number	9026-30-6
Databases
IntEnz	IntEnz view
BRENDA	BRENDA entry
ExPASy	NiceZyme view
KEGG	KEGG entry
MetaCyc	metabolic pathway
PRIAM	profile
PDB structures	RCSB PDB PDBe PDBsum
Gene Ontology	AmiGO / EGO
Search PMC articles PubMed articles NCBI proteins

In enzymology, a polynucleotide adenylyltransferase (EC 2.7.7.19) is an enzyme that catalyzes the chemical reaction

ATP + RNAn $\rightleftharpoons$ diphosphate + RNAn⁺1

Thus, the two substrates of this enzyme are ATP and RNA, whereas its two products are diphosphate and RNA with an extra adenosine nucleotide at its 3' end.

Naming

This enzyme belongs to the family of transferases, specifically those transferring phosphorus-containing nucleotide groups (nucleotidyltransferases). The systematic name of this enzyme class is ATP:polynucleotide adenylyltransferase.

Other names in common use include:

• NTP polymerase
• RNA adenylating enzyme
• AMP polynucleotidylexotransferase
• ATP-polynucleotide adenylyltransferase
• ATP:polynucleotidylexotransferase
• Poly(A) polymerase
• Poly(A) synthetase
• Polyadenylate nucleotidyltransferase
• Polyadenylate polymerase
• Polyadenylate synthetase
• Polyadenylic acid polymerase
• Polyadenylic polymerase
• Terminal riboadenylate transferase
• Poly(A) hydrolase
• RNA formation factors
• PF1
• Adenosine triphosphate:ribonucleic acid adenylyltransferase

Function

This enzyme is responsible for the addition of the 3' polyadenine tail to a newly synthesized pre-messenger RNA (pre-mRNA) molecule during the process of gene transcription. The protein is the final addition to a large protein complex that also contains smaller assemblies known as the cleavage and polyadenylation specificity factor (CPSF) and cleavage stimulatory factor (CtSF) and its binding is a necessary prerequisite to the cleavage of the 3' end of the pre-mRNA. After cleavage of the 3' signaling region that directs the assembly of the complex, PAP adds the polyadenine tail to the new 3' end.

The rate at which PAP adds adenine nucleotides is dependent on the presence of another regulatory protein, PABPII (poly-adenine binding protein II). The first few nucleotides added by PAP are added very slowly, but the short polyadenine tail is then bound by PABPII, which accelerates the rate of adenine addition by PAP. The final tail is about 200-250 adenine nucleotides long.

PAP is phosphorylated by mitosis-promoting factor , a key regulator of the cell cycle. High phosphorylation levels decrease PAP activity.

Structural studies

As of late 2007, 27 structures have been solved for this class of enzymes, with PDB accession codes 1AV6, 1B42, 1BKY, 1EAM, 1EQA, 1F5A, 1FA0, 1JSZ, 1JTE, 1JTF, 1P39, 1Q78, 1Q79, 1V39, 1VFG, 1VP3, 1VP9, 1VPT, 2GA9, 2GAF, 2HHP, 2O1P, 2Q66, 2VP3, 3MAG, 3MCT, and 4DCG.

References

• August JT, Ortiz PJ, Hurwitz J (December 1962). "Ribonucleic acid-dependent ribonucleotide incorporation. I. Purification and properties of the enzyme". J. Biol. Chem. 237: 3786–93. PMID 13965521. 
• Edmonds M and Abrams R (1960). "Polynucleotide biosynthesis: formation of a sequence of adenylate units from adenosine triphosphate by an enzyme from thymus nuclei". J. Biol. Chem. 235 (4): 1142–1149. 
• Gottesman ME, Canellakis ES (1966). "The terminal nucleotidyltransferases of calf thymus nuclei". J. Biol. Chem. 241 (19): 4339–52. PMID 4288534. 
• Krakow Js, Coutsogeorgopoulos C, Canellakis ES (1962). "Studies on the incorporation of deoxyribonucleic acid". Biochim. Biophys. Acta. 55 (5): 639–50. doi:10.1016/0006-3002(62)90842-9. PMID 14459258. 
• Mans RJ, Walter TJ (1971). "Transfer RNA-primed oligoadenylate synthesis in maize seedlings. II Primer, substrate and metal specificities and size of product". Biochim. Biophys. Acta. 247 (1): 113–21. PMID 4946277. 
• Sheldon R, Jurale C, Kates J (1972). "Detection of polyadenylic acid sequences in viral and eukaryotic RNA(polu(U)-cellulose columns-poly(U) filters-fiberglass-HeLa cells-bacteriophage T4)". Proc. Natl. Acad. Sci. U.S.A. 69 (2): 417–21. doi:10.1073/pnas.69.2.417. PMC 426470. PMID 4501121. 
• Colgan DF, Murthy KG, Prives C, Manley JL (November 1996). "Cell-cycle related regulation of poly(A) polymerase by phosphorylation". Nature 384 (6606): 282–5. doi:10.1038/384282a0. PMID 8918882.