Many early
mRNA species of bacteriophage T4 are not synthesized after
infection of Escherichia coli in the presence of
chloramphenicol. This has been interpreted as a need for T4
protein(s) to be synthesized to allow expression of some early genes, e.g., those for
deoxycytidinetriphosphatase, deoxynucleosidemonophosphate
kinase and
UDP-glucose-
DNA beta-glucosyltransferase. In the experiments described here, early
mRNA of bacteriophage T4 was allowed to accumulate during
chloramphenicol treatment. After the addition of
rifampin to inhibit further
RNA synthesis, and subsequent removal of
chloramphenicol, the accumulated
mRNA was permitted to express itself into measured
enzyme activities. It was shown that the early
mRNA species coding for
deoxycytidinetriphosphatase and
UDP-glucose-
DNA beta-glucosyltransferase could be formed in the presence of
chloramphenicol if the E. coli host cell carried a mutation in the structural gene for the
RNA chain termination
factor rho. This was interpreted to mean that T4
protein(s) with anti-rho activity is normally required for the expression of these two early genes. An altered
rho-factor could not, however, relieve the need of phage
protein synthesis for the formation of another early
mRNA, that coding for deoxynucleosidemonophosphate
kinase. In this case the mot gene of T4 seemed to be involved, since the primary
infection of E. coli cells with the mot gene mutant tsG1 did not allow subsequent
deoxynucleoside monophosphate kinase mRNA synthesis after wild-type phage
infection in the presence of
chloramphenicol. In control experiments,
deoxynucleoside monophosphate kinase mRNA synthesis induced by wild-type phage superinfecting in the presence of
chloramphenicol was facilitated by the primary
infection with T4 phage containing an unmutated mot gene.