THE BACTERIOPHAGE-P1 LYTIC REPLICON - DIRECTIONALITY OF REPLICATION AND CIS-ACTING ELEMENTS

We have identified the direction of replication of a bacteriophage P1 lytic replicon. This was accomplished by constructing lambda P1 lysoge ns that contain a functional P1 lytic replicon and analysing which of two nearby bacterial DNA markers flanking the lambda prophage were amp lified when that replicon was activated. We demonstrate that both DNA markers are coordinately amplified, a result consistent with lytic rep lication proceeding in a bidirectional fashion. To analyze the role of various elements comprising the lytic replicon, we assessed the abili ty of a wild type replicon to complement a defective replicon that con tains a transposon inserted between an essential lytic replication gen e (repL) and the promoter (P53) at which transcription of that gene is initiated. We show that the wild type replicon cannot complement the mutant replicon. The simplest hypothesis to explain this result is tha t either P53 or repL protein functions primarily in cis for the replic on to operate.