Initiation of Lambda DNA Replication in vitro Promoted by Isolated P-Gene Product

Abstract

The product of the P gene of bacteriophage .lambda. was isolated from heat-induced .lambda.-lysogenic Escherichia coli cells. It bound to DNA, was devoid of nuclease activity acting on double-stranded .lambda. DNA and of nicking/closing activity. Initiation of .lambda. DNA replication promoted by the P-gene product in a complementation assay in vitro was sensitive to rifampicin. Sedimentation analysis of the products and their hybridization to separated .lambda. DNA strands indicated that .lambda. DNA was formed in a reaction similar to ring-to-ring replication in vivo. The reaction was symmetric from the beginning, i.e., both .lambda. DNA strands were copied without delay.