Induction of an endonuclease by some substitution and deletion variants of phage lambda

The phage promoter responsible for the expression of the inserted beta-galactosidase gene in bacteriophage lambda plac5

The lac transducing phage, lambda plac5, carries a segment of the E. coli lac operon on the left side of the b2 region of the lambda phage. In the absence of additional cyclic AMP, beta-galactosidase can only be expressed from the phage promoter, and the expression of the inserted lac promoter is suppressed. This phage promoter responsible for beta-galactosidase synthesis is shown to be under the control of the cI and N gene products; however, the repressive action of the cro gene product at high multiplicity of infection is not observed although some turn off at very late time is detected. To pin down this phage promoter, results described in this communication and those described elsewhere can rule out the promoter PI, PR, P'R, and the promoter PL also looks rather unlikely. No firm identification of this phage promoter has been made, but the promoter(s) in the b2 region (the b2 promoter) is proposed. The phage promoter responsible for beta-galacrosidase synthesis is shown to be a weak promoter, requires the Q gene product or one (or more) of the late gene products for activation, and the time of expression is very late.

A rightward promoter to the left of the att site of lambda phage DNA: possible participant in site-specific recombination

The binding has been studied of Escherichia coli RNA-polymerase to the fragments of lambda DNA obtained by digestion with restriction endonucleases BsuI, HindIII, BamHI, EcoRI and HindII + III. There are at least six sites of RNA-polymerase binding in the b2-region. In vitro transcription of those BsuI-fragments of the b2-region which contain six binding sites is rightward. Therefore, the fragments contain promoters rather than mere RNA-polymerase binding sites. One of the promoters of the b2 region named patt was calculated to be about 50 bp to the left of the att site. We postulate that this promoter might correspond to the hef-target which was described as important for the site-specific recombination.