Perturbation of the SOS Response of Escherichia coli by Plasmids Carrying Truncated recA Genes
Several models for the regulation of E. coli recA + gene expression and induction of qS functions envisage that the recA + gene is repressed by the lexA + gene product. Positive control is thought to occur by “activation” of the basal level of recA + protein so that it in2ctivates both lexA + protein and the repressors of the SOS functions2-5. Such models predict that an excess of recA promotor-operato sequences would titrate lexA + repression of the chromosomal recA + gene2. The result would be escape synthesis of recA + protein,and perhaps easier inducibility of SOS functions.To test these naive predictions recA control sequences were introduced into E. coli by transformation with pBR322 derivatives, carr/ing the recA control sequence and 100%, 75% and 20% of the recA + structural gene (fig.l) pgR1453 and pDR1461 were very generously supplied by Dr. Dean Rupp6.
KeywordsrecA Protein lexA Gene Expectation Transformation pBR322 Site pBR322 Derivative
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