THE ROLE OF THE OOP ANTISENSE RNA IN COLIPHAGE LAMBDA DEVELOPMENT

We have made a derivative of bacteriophage lambda that makes no OOP antisense RNA. The mutant phage carries a point mutation that inactivates the OOP promoter, p(o). The phages lambda-+ and lambda-p(o)- have identical plaque morphologies, one-step growth curves, and frequencies of lysogenization of a sensitive host. OOP RNA synthesis is weakly repressed by the Escherichia coli LexA protein. Consonant with this inducibility of OOP RNA synthesis by ultraviolet light, we find a two-fold greater phase burst following ultraviolet induction of a lambda-+ than of a lambda-p(o)- prophage. In lambda-+ infections, OOP RNA causes two cleavage events in cII mRNA: one is in the 3'-end of the coding region, and the second is in the intercistronic region between the cII and O genes. The cII gene fragments are subject to additional hydrolytic events, and cII mRNA levels are several-fold lower in lambda-+ than in lambda-p(o)- infections late in the infection cycle. However, O mRNA levels are almost unaffected by the p(o)- mutation.