title: Mechanism of pppA(2'p5'A)n2'p5'AOH synthesis in extracts of interferon-treated HeLa cells.
abstract: Treatment of HeLa cells with interferon results in the induction of an enzymatic activity designated 2'5'oligo(A) polymerase. The polymerase requires continuous presence of double-stranded RNA (dsRNA) for activity, since degradation of dsRNA abolishes synthesis of the oligomeric series pppA(2'p5'A)n. These oligonucleotides are formed initially at a constant rate with dimer synthesized faster than trimer, and the latter faster than tetramer. After 45 min, accumulation of the dimer declines whereas that of other oligomers still proceeds at a linear rate. These results suggest that an oligomer remains associated with the enzyme for possible consecutive additions of adenylate, since no significant accumulation of dimer precedes synthesis of trimer. The relative amounts of the different oligomers found at the end of a reaction may reflect an increasing probability of release as the oligomers are elongated. The accumulation of dimer, however, decreases when it becomes a substrate for adenylate addition; incorporation of isolated dimer into 2'5'-oligo(A) was directly shown. Other nucleotides with a blocked p5'A terminus, like A5'ppppp5'A and NADH, can serve as adenylate acceptors in the presence of dsRNA. The adenosine triphosphates 2'-dATP and 3'-dATP are not incorporated efficiently into 2'5'-oligo(A) and inhibit its synthesis.
mesh_terms: D015088:2',5'-Oligoadenylate Synthetase; D000227:Adenine Nucleotides / Q000096:biosynthesis*; D004790:Enzyme Induction; D006367:HeLa Cells / Q000187:drug effects / Q000201:enzymology; D006801:Humans; D007372:Interferons / Q000494:pharmacology*; D007700:Kinetics; D009711:Nucleotides / Q000494:pharmacology; D009841:Oligonucleotides / Q000096:biosynthesis*; D009843:Oligoribonucleotides / Q000096:biosynthesis*; D011118:Polynucleotide Ligases / Q000096:biosynthesis*
chemical_list: D000227:Adenine Nucleotides; D009711:Nucleotides; D009841:Oligonucleotides; D009843:Oligoribonucleotides; C018445:adenosine triphosphate-2',5'-adenosine monophosphate; D007372:Interferons; D015088:2',5'-Oligoadenylate Synthetase; D011118:Polynucleotide Ligases