RT Journal Article SR Electronic T1 Effect of 6-Mercaptopurine Ribonucleotides on DNA-Dependent RNA Polymerase Activity JF Molecular Pharmacology JO Mol Pharmacol FD American Society for Pharmacology and Experimental Therapeutics SP 503 OP 506 VO 18 IS 3 A1 RUSSELL T. KAWAHATA A1 CHARLES A. HOLMBERG A1 BENNIE I. OSBURN A1 LINDA F. CHUANG A1 RONALD Y. CHUANG YR 1980 UL http://molpharm.aspetjournals.org/content/18/3/503.abstract AB 6-Mercaptopurine ribonucleoside 5'-triphosphate was found to be an inhibitor of DNA-dependent RNA polymerases from Escherichia coli and chicken myeloblastosis cells. The inhibitor appears to compete with GTP for its binding to RNA polymerase, resulting in a reduction of RNA chain initiations. Neither 6-mercaptopurine ribonucleoside nor its monophosphate derivative caused the inhibition. These studies suggest that the antineoplastic action of 6-mercaptopurine may in part be owing to the inhibition of the activity of DNA-dependent RNA polymerase, resulting in an inhibition of cellular RNA synthesis.