title: Presence of 2',5'-oligo(A) and of enzymes that synthesize, bind, and degrade 2',5'-oligo(A) in HeLa cell nuclei.
abstract: Nuclei prepared from HeLa cells by lysis with nonionic detergents or by a nonaqueous fractionation procedure were assayed for enzymatic activities which synthesize, bind, and degrade 2',5'-oligo(A). Isolated nuclei synthesized micromolar concentrations of 2',5'-oligo(A) when incubated with poly(inosinic) . poly(cytidylic) acid. The products of nuclear synthesis were identified with authentic 2',5'-oligo(A) by several criteria. The nuclei synthesized nanomolar amounts of 2',5'-oligo(A) even when incubated without added double-stranded RNA. These oligonucleotides were identified by their pattern of degradation with different nucleases and by a specific competition-binding assay. This assay revealed the presence in nuclei of an activity which binds 2',5'-oligo(A) with an affinity constant similar to that of the cytoplasmic binding activity previously identified with the 2',5'-oligo(A)-dependent endoribonuclease (Nilsen, T. W., Wood, D. L., and Baglioni, C. (1981) J. Biol. Chem. 256, 10751-10754). The nuclei had also an activity which degraded 2',5'-oligo(A). Finally, unincubated nuclei isolated by the nonaqueous fractionation procedure contained detectable concentrations of 2',5'-oligo(A). These results show that an activator of the enzyme which synthesize 2',5'-oligo(A) is present in nuclei and that these oligonucleotides are normally formed in HeLa cells, and suggest a possible role for the 2',5'-oligo(A)-activated endoribonuclease in nuclear RNA metabolism.
mesh_terms: D015088:2',5'-Oligoadenylate Synthetase; D000227:Adenine Nucleotides / Q000378:metabolism*; D001667:Binding, Competitive; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism*; D004722:Endoribonucleases; D006367:HeLa Cells / Q000187:drug effects / Q000201:enzymology; D006801:Humans; D007372:Interferons / Q000494:pharmacology; D007700:Kinetics; D009713:Nucleotidyltransferases / Q000378:metabolism*; D009841:Oligonucleotides / Q000378:metabolism*; D009843:Oligoribonucleotides / Q000378:metabolism*; D012260:Ribonucleases / Q000378:metabolism*
chemical_list: D000227:Adenine Nucleotides; D009841:Oligonucleotides; D009843:Oligoribonucleotides; C023505:2',5'-oligoadenylate; D007372:Interferons; D009713:Nucleotidyltransferases; D015088:2',5'-Oligoadenylate Synthetase; D004722:Endoribonucleases; D012260:Ribonucleases; C031956:2-5A-dependent ribonuclease