title: The enzymatic conversion of 3'-phosphate terminated RNA chains to 2',3'-cyclic phosphate derivatives.
abstract: The enzyme, RNA cyclase, has been purified from cell-free extracts of HeLa cells approximately 6000-fold. The enzyme catalyzes the conversion of 3'-phosphate ends of RNA chains to the 2',3'-cyclic phosphate derivative in the presence of ATP or adenosine 5'-(gamma-thio)triphosphate (ATP gamma S) and Mg2+. The formation of 1 mol of 2',3'-cyclic phosphate ends is associated with the disappearance of 1 mol of 3'-phosphate termini and the hydrolysis of 1 mol of ATP gamma S to AMP and thiopyrophosphate. No other nucleotides could substitute for ATP or ATP gamma S in the reaction. The reaction catalyzed by RNA cyclase was not reversible and exchange reactions between [32P]pyrophosphate and ATP were not detected. However, an enzyme-AMP intermediate could be identified that was hydrolyzed by the addition of inorganic pyrophosphate or 3'-phosphate terminated RNA chains but not by 3'-OH terminated chains or inorganic phosphate. 3'-[32P](Up)10Gp* could be converted to a form that yielded, (Formula: see text) after degradation with nuclease P1, by the addition of wheat germ RNA ligase, 5'-hydroxylpolynucleotide kinase, RNA cyclase, and ATP. This indicates that the RNA cyclase had catalyzed the formation of the 2',3'-cyclic phosphate derivative, the kinase had phosphorylated the 5'-hydroxyl end of the RNA, and the wheat germ RNA ligase had catalyzed the formation of a 3',5'-phosphodiester linkage concomitant with the conversion of the 2',3'-cyclic end to a 2'-phosphate terminated residue.
authors.forename: D
authors.initials: D
authors.lastname: Reinberg
authors.forename: J
authors.initials: J
authors.lastname: Arenas
authors.forename: J
authors.initials: J
authors.lastname: Hurwitz
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology; D006367:HeLa Cells / Q000378:metabolism; D006801:Humans; D008025:Ligases / Q000302:isolation & purification / Q000378:metabolism*; D009694:Nucleic Acid Precursors / Q000378:metabolism; D012313:RNA / Q000096:biosynthesis* / Q000378:metabolism; D011130:RNA Ligase (ATP) / Q000378:metabolism; D012326:RNA Splicing; D000079962:RNA, Circular; D014908:Triticum / Q000378:metabolism
chemical_list: D009694:Nucleic Acid Precursors; D000079962:RNA, Circular; D012313:RNA; D000255:Adenosine Triphosphate; D008025:Ligases; C037451:RNA 3'-terminal phosphate cyclase; D011130:RNA Ligase (ATP)