IRREVERSIBLE INHIBITION OF NUCLEAR EXORIBONUCLEASE BY THYMIDINE-3'-FLUOROPHOSPHATE AND P-HALOACETAMIDOPHENYL NUCLEOTIDES

Exoribonuclease purified from Ehrlich ascites tumor cell nuclei and in intact HeLa cell nuclei is irreversibly inactivated by low concentrations of p-bromo- and p-iodoacetamnidophenyl nucleotides and by thymidine-3′- fluorophosphate. Iodoacetate, bromoacetate, and thymidine-5′- fluorophosphate do not affect the enzyme. Although p-haloacetamidophenyl nucleotides inactivate ribonucleic acid polymerase of isolated HeLa cell nuclei, thymidine-3′-fluorophosphate does not affect the activity of this enzyme in vitro.