DEFINING THE SOS OPERON OF COLIPHAGE-186

We have sequenced the LexA-controlled operon of coliphage 186 that car ries the tum gene, whose product is necessary for UV induction of the 186 prophage. The operon consists of orf95 and orf97, and we have iden tified orf95 as the tum gene. The major translation products from orf9 5 result from internal initiations and modulate Tum activity. Turn is the product of the full-length Orf95 protein. The second gene of the o peron, orf97, is of unknown function but, while it has little effect o n prophage induction, its presence in the cell totally blocks infectio n of that cell by 186. (C) 1996 Academic Press, Inc.