New late gene, dar, involved in the replication of bacteriophage T4 DNA. II. Overproduction of DNA binding protein (gene 32 protein) and further characterization.

We have previously shown that the arrested DNA synthesis of mutant defective in T4 phage gene 59 can be reversed by a mutation in dar. In this paper, we have examined the effect of the dar mutation on the kinetics of gene 32 protein (DNA binding protein) synthesis, DNA packaging, progeny formation, and several other porcesses. Several lines of evidence are presented showing that the regulation of synthesis of gene 32 protein is abnormal in dar 1-infected cells. In these cells, gene 32 protein, an early protein, is also expressed late in the infectious cycle. Our data also indicate that the packaging og DNA into T4 phage heads is delayed in dar mutant-infected cells, and this in turn results in a 6- to 8-min delay in intracellular progeny formation, although the synthesis of late proteins appears to be normal, as shown by gel electrophoresis. We have also studied the phenotypes of the double mutant dar-amC5 (gene 59). The increased sensitivity to hydroxyurea caused by a mutation in the dar gene can be alleviated by a second mutation in gene 59, but an increased sensitivity to UV irradiation caused by a mutation in gene 59 cannot be alleviated by a second mutation in the dar gene. Therefore, the double mutant still exhibits abnormalities in the repair of UV lesions.