The role of the OOP antisense RNA in coliphage λ development

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Abstract
We have made a derivative of bacteriophage λ that makes no OOP antisense RNA. The mutant phage carries a point mutation that inactivates the OOP promoter, po. The phages λ+ and λp 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 phage burst following ultraviolet induction of a λ+ than of a λp o− prophage. In λ+ infections, OOP RNA causes two cleavage events in dl mRNA: one is in the 3′ ‐end of the coding region, and the second is in the intercistronic region between the dl and O genes. The dl gene fragments are subject to additional hydrolytic events, and dl mRNA levels are several‐fold lower in λ+ than in λp o‐ infections late in the infection cycle. However, O mRNA levels are almost unaffected by the P o‐ mutation.