Relief of transcriptional polarity by a mutation that creates a promoter in the hisG gene of Salmonella typhimurium LT2

Abstract

Six mutant strains were independently isolated in Salmonella typhimurium as non-polar revertants of a polar Tn10 insertion in hisG. DNA sequence analysis showed that all six mutants result from the same nucleotide alteration: a G/C to A/T transition 4 bp from the end of the hisG coding sequence. We present data suggesting that the mutation (hisG10225) acts by creating a new transcriptional initiation signal. Furthermore, the hisG10225 mutation renders the hisG gene product cold sensitive.