Novobiocin inhibits the self-splicing of the primary transcripts of T4 phage thymidylate synthase gene

Abstract

Effects of the antibiotic novobiocin on the self-splicing of primary transcripts of the phage T4 thymidylate synthase gene (td) have been investigated. Novobiocin at 10 mM concentration inhibited the splicing by about 5% but at 40 mM concentration the splicing rate was inhibited by about 50%. The novobiocin inhibition of the self-splicing reaction was not reversed even at a high concentration (200 μM) of guanosine. However, increasing the Mg²⁺ ion concentrations up to 20 mM almost fully restored the splicing activity to the normal splicing level. The double reciprocal plot analysis demonstrated that novobiocin acts as a mixed noncompetitive inhibitor for the td intron RNA with a K _i of 90 mM. The splicing inhibition by novobiocin was strongly dependent on Mg²⁺ ion concentration, indicating electrostatic interactions with the td intron RNA. It is likely that the antibiotic novobiocin may interfere with the catalytic actions of Mg²⁺ ion in the splicing reaction of the td intron RNA.