A LATE EXCLUSION OF BACTERIOPHAGE-T4 CAN BE SUPPRESSED BY ESCHERICHIA-COLI GROEL OR RHO

A LitCon mutation in Escherichia coli TU6 results in exclusion of bact eriophage T4 during the late, morphogenetic stage of its development a t low temperatures. DNA was synthesized continuously in the infected c ells, but less than 10% of the DNA made by 90 min after infection was packaged into DNAase-resistant particles, few viable phage were formed , and the cells lysed poorly. The exclusion could be relieved by condi tions leading to elevated levels, determined immunologically, of the E . coli Rho protein (believed to be involved in regulation of T4 transc ription), or chromosomally encoded E. coli GroEL (a chaperone known to be involved in phage assembly), or by supplying GroEL in trans from a plasmid. The two suppressing proteins appeared to act independently o f each other. GroEL-suppression restored packaging to normal levels, p erhaps by preventing GP23 from activating the host Lit protein; in add ition DNA synthesis was delayed and reduced and cell lysis enhanced, d emonstrating involvement of GroEL in both these processes. Rho suppres sion was less efficient. Since both transcription-termination-proficie nt and transcription-termination-deficient Rho suppressed, the results raise the possibility that Rho has a role during T4 development not d irectly involving transcription regulation.