Slow switchover from host RNA synthesis to bacteriophage RNA synthesis after infection of Escherichia coli with a T4 mutant defective in the bacteriophage T4-induced unfolding of the host nucleoid.

Most, if not all, host RNA synthesis was shut off after infection of Escherichia coli strain B/5 with a bacteriophage T4 multiple mutant defective in the abilities to induce (i) unfolding of the host nucleoid (unf-), (ii) nuclear disruption (ndd-), and (iii) host DNA degradation (denA-, denB-). The shutoff of host RNA synthesis and turn-on of phage RNA synthesis were slower after infection of E. coli with unf- phage than after infection with unf+ phage. This delay in the switchover from host RNA synthesis to phage RNA synthesis in unf- infections did not result in a measurable delay in the onset of nuclear disruption, deoxyribonucleoside monophosphate kinase synthesis, or DNA synthesis. unf39 did not complement alc (allows late transcription on cytosine-containing DNA) mutants, supporting the proposal of Sirotkin et al. [Nature (London) 265:28-32, 1977] that alc and unf are possibly the same gene.