title: RNA 3'-terminal phosphate cyclase activity and RNA ligation in HeLa cell extract.
abstract: HeLa cell extract contains RNA ligase activity that converts linear polyribonucleotides to covalently closed circles. RNA substrates containing 2',3'-cyclic phosphate and 5'-hydroxyl termini are circularized by formation of a normal 3',5' phosphodiester bond. This activity differs from a previously described wheat germ RNA ligase which circularizes molecules with 2',3'-cyclic and 5' phosphate ends by a 2'-phosphomonester, 3',5'-phosphodiester linkage (Konarska et al., Nature 293, 112-116, 1981; Proc. Natl. Acad. Sci. USA 79, 1474-1478, 1982). The HeLa cell ligase can also utilize molecules with 3'-phosphate ends. However, in this case ligation is preceded by an ATP-dependent conversion of the 3'-terminal phosphate to the 2',3' cyclic form by a novel activity, RNA 3'-terminal phosphate cyclase. Both RNA ligase and RNA 3'-terminal phosphate cyclase activities are also present in extract of Xenopus oocyte nuclei, consistent with a role in RNA processing.
mesh_terms: D000818:Animals; D002467:Cell Nucleus / Q000201:enzymology; D005260:Female; D006367:HeLa Cells / Q000201:enzymology; D006801:Humans; D007700:Kinetics; D008025:Ligases / Q000378:metabolism*; D009865:Oocytes / Q000201:enzymology; D011118:Polynucleotide Ligases / Q000378:metabolism*; D011130:RNA Ligase (ATP) / Q000378:metabolism*; D013045:Species Specificity; D013379:Substrate Specificity; D014981:Xenopus
chemical_list: D008025:Ligases; C037451:RNA 3'-terminal phosphate cyclase; D011118:Polynucleotide Ligases; D011130:RNA Ligase (ATP)