Q-mediated late gene transcription of bacteriophage lambda: RNA start point and RNase III processing sites in vivo.

The location of the RNA start point of in vivo Q-activated late gene RNA of bacteriophage lambda has been determined to be identical to the start point of in vitro 6 S RNA. The 6 S RNA is made early in infection and is efficiently antiterminated by Q. Two RNase III cut sites are located within Q-dependent RNA sequences, 209 and 270 bp from the beginning of the late transcript, and lie on the stem of an inverted repeat which has features in common with previously described RNase III processing sites. This is the third example of RNase III cut sites immediately downstream of transcription termination points in lambda, the others being antiterminated N gene mRNA and int gene mRNA.