Gene-fusion and the analysis of genetic control signals
The approach of gene-fusion was used to analyse genetic control signals. Vectors carrying the trp/lac W205 substitution were constructed to facilitate the fusion vitro of promoters, terminators and other control signals to the lacZ gene of E. coli. Two systems were developed using either a lambda or pBR322 replicon. The plasmid system was developed further to provide probes for promoter and terminator sequences. Restriction analysis of these vectors added to the physical data on the trp/lac W205 fusion. The lambda system was used to analyse transcriptional termination in the b2 region of the phage. This central region was shown to contain terminators insensitive to the anti-terminator proteins specified by the lambda N and Q genes. Gene-fusions were used to examine the control of late gene expression of phage lambda. This expression was dependent on the activity of the gene product. This protein was unusual, being almost completely cis-specific. Transcription of the late genes is initiated in the "6S region" adjacent to the lambda Q gene. This region was cloned into a trp/lac plasmid and its effect was monitored by expression from the lacZ gene fused to this segment. Expression of lacZ from this promoter was limited by a strong terminator 194 base-pairs downstream. However, a weak positive effect was observed in the presence of the lambda Q gene product, mapping the site of Q action, Qat, in or near the 6S region.