PRIMARY AND SECONDARY REPLICATION SIGNALS IN BACTERIOPHAGE λ AND IS 5 INSERTION ELEMENT INITIATION SYSTEMS

A comparison of the available lambdoid origin sequences allows to point out several structural features in common with the DNA sequence of the phage G4 intercistronic region between genes F and G, which can be interpreted as recognition elements of a primase promoter sequence. These leading strand initiation signals are located in leftward orientation on the A-rich strand of all lambdoid origins, and by comparison with G4 require a single-stranded binding sequence, which appears to result from transcriptional activation. Binding of 0 protein to the origin interferes with transcription across ori , which therefore, has to precede these ori/0 interactions.