T4 DNA replication and viral gene expression

The normal dependence of “late” T4 gene expression on concurrent viral DNA replication is circumvented in cells infected with a triple mutant in which viral DNA polymerase, DNA ligase, and the exonuclease functions of genes 46 or 47 are defective. Acrylamide gel electrophoresis of labeled proteins from infected cells has made possible an extension of the analysis of replication-uncoupled T4 protein synthesis. We find a number of late T4 proteins synthesized: the products of genes 34, 37, 18, 23 and 24. Processing of the gene 23 product, normally headassembly dependent, occurs, but with considerably diminished efficiency compared to wild-type infection. Late T4 protein synthesis in replication-uncoupled infection retains a requirement for T4 gene 33 and gene 55 function. Finally, a number of “early” T4 gene products, normally shut off late in wildtype infection, continue to be synthesized late in replication-uncoupled infection, concurrently with the late proteins.