Inhibition of transcription by isonicotinic acid hydrazide

Isonicotinic acid hydrazide (INH) reacts with the CMP moiety of a polynucleotide at slightly acid and alkaline pH. The reaction product, when used as a template in the cell-free transcription step, greatly diminishes the incorporation of GMP. In this system we were not able to show that INH -- in contrast with hydrazin -- is potentially capable of producing point mutations, since noncomplementary incorporation could not be observed with a poly(C)/INH adduct as template. Hydrazine could not be detected when INH was incubated with liver-cell fractions.