Regulation of gene 32 expression during bacteriophage T4 infection of Escherichia coli.

The gene 32 protein of the bacteriophage T4 plays an important role in genetic recombination, DNA repair, and DNA replication; the protein functions in these processes by virtue of a strong binding capacity for single-stranded DNA. During infections of Escherichia coli by bacteriophage carrying amber of temperature-sensitive mutations in gene 32, the altered gene 32 protein (that is, the amber fragment of the missense polypeptide) is synthesized at greatly elevated rates. During infections by phages that are mutant in other genes (and wild type in gene 32), gene 32 expression is coupled to the quantity of single-stranded DNA produced during the infection. The data are consistent with a model in which the gene 32 protein binds preferentially to all available single-stranded DNA. When all available single-stranded DNA is complexed with gene 32 protein, free gene 32 protein represses its own synthesis. The high level expression of altered gene 32 proteins (amber fragments or missense polypeptides) is a direct consequence of the proposed autoregulation.