Key words RNA polymerase α subunit
Phage λ development
Phage λ promoters
Positive control of transcription
Springer Online Journal Archives 1860-2000
Abstract The C-terminus of the α subunit of Escherichia coli RNA polymerase is known to function in transcriptional activation at certain promoters. This region was previously shown to be necessary for full activation of the p E promoter by the phage λ CII protein in vitro. In this work we investigated the inability of phage λ to follow the lysogenic pathway in cells carrying the point mutation rpoA341 (a change of lysine 271 to glutamic acid). We found that neither overexpression of the cII gene nor stabilisation of the CII protein by the can1 mutation or by cIII gene overexpression was able to suppress the block in lysogenisation. In contrast, the λcin1 phage, which carries a CII-independent promoter for the expression of the cI gene, was able to efficiently lysogenise the rpoA341 mutant strain. Furthermore, the rpoA341 mutation prevented the activation of p E-lacZ and p I-lacZ transcriptional fusions by CII. Therefore we conclude that transcriptional activation by the cII gene product is abolished by the rpoA341 mutation, most probably due to impaired interaction between the CII activator and mutant RNA polymerase. The inability of RNA polymerase to respond to CII results in the impairment of lysogenisation of the rpoA341 mutant by phage λ.
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