An unusual RNA polymerase binding site in the immunity region of phage lambda.

RNA polymerase binds very tightly at a site called Brex in the lambda immunity region, to the left of the rex gene and about 600 nucleotides to the right of PL. The complex formed is resistant to 1 M NaCl in the absence of nucleotide triphosphate. While in vitro little or no transcription is observed from Brex, in vivo, when inserted in a plasmid vector which allows detection of its activity, it acts as an efficient promoter.

Control of expression of a cloned yeast (Saccharomyces cerevisiae) gene (trp5) by a bacterial insertion element (IS2).

A hybrid ColE1 plasmid [pYe(trp5)1], containing a yeast DNA segment that complements auxotrophic point mutations and deletions in the Escherichia coli tryptophan synthetase gene (trpAB), has been isolated. Expression of the yeast tryptophan synthetase activity from the cloned yeast gene (trp5) is relatively inefficient in E. coli, as measured by growth rates of trpAB/pYe(trp5)1 strains on minimal media lacking tryptophan and by enzyme assays.

Lambda repressor regulates the switch between PR and Prm promoters.

The DNA region containing the Or operator, Pr and Prm promoters and their transcription initiations is sequenced. By binding to Or, repressor turns off Pr, turns on Prm and at higher concentrations turns off Prm, regulating its own synthesis. Prm mRNA is unique in beginning immediately with the initiation of translation, without a preceding leader sequence.

Sequence of the PR promoter of phage lambda.

The RNA polymerase binding site from the lambda PR promoter was isolated and sequenced. This DNA fragment contains the transcription initiation site and shares 25 nucleotides with OR. The sequence preceding the initiation site suggests that the promoter recognition site is not identical with the tight binding and initiation site.