Synthesis of protein in a purine-requiring Escherichia coli infected with bacteriophage T2

Regulation of expression of late genes of bacteriophage T5

Amber mutants of bacteriophage T5 defective in gene C2 have been characterized. The product of this gene is required for the normal turn-on of synthesis of late RNA's and proteins, and, apparently, for the normal continued synthesis of early RNA's and proteins during late stages of infection. The inability of nonpermissive cells to synthesize any proteins, either late or early, during the late period after infection with a C2-mutant is not due to premature lysis of the infected cells, to a depletion of the cellular energy supply, or to degradation of phage DNA at late times. A possible role for the product of gene C2 in early and late transcription of the viral genome is suggested.

Requirement of a phage-induced 5'-exonuclease for the expression of late genes of bacteriophage T5

Amber mutants of bacteriophage T5 defective in gene D15, which codes for a 5'-exonuclease, do not express late genes. Electrophoretic separation in sodium dodecyl sulfate-polyacrylamide gels of the proteins induced by this mutant in nonpermissive Escherichia coli show a virtual absence of late proteins. Synthesis of lysozyme and serum-blocking power is very low whereas the extent of synthesis of an early enzyme, deoxyribonucleoside monophosphokinase, is similar to that in wild-type infections. It is proposed that one requirement for the expression of late T5 genes is the introduction of gaps or nicks in the T5 DNA so that late transcription can occur.