MUTATIONS REDUCING THE ACTIVITY OF C17, A PROMOTER OF PHAGE-LAMBDA FORMED BY A TANDEM DUPLICATION

The isolation of 4 independently selected mutations (scs) in the c17 promoter of phage .lambda. that reduce or eliminate the promoter activity was reported. The c17 promoter is not normally present in .lambda., and was generated by a tandem duplication which creates a Pribnow Box, a heptamer sequence implicated in promoter activity. This sequence is located upstream from the site of transcription initiation and is present, with some variation, in all promoters whose sequences were determined. Analysis of the c17 duplications carrying the scs mutations reveals that 3 of these mutants carry single base-pair changes in the most highly conserved base pairs of the Pribnow Box and that the other mutation is a reversion to the wild-type sequence in this region (i.e., a loss of the duplicated base pairs).