Accumulation of Sigma S due to enhanced synthesis and decreased degradation in acidic phospholipid-deficient Escherichia coli cells

作者：Uchiyama Junji; Sasaki Yu; Nagahama Hideki; Itou Aya; Matsuoka Satoshi; Matsumoto Kouji^*; Hara Hiroshi

来源：FEMS Microbiology Letters, 2010, 307(2): 120-127.

DOI：10.1111/j.1574-6968.2010.01964.x

• Escherichia coli
• sigma S
• acidic phospholipids
• pgsA

The Escherichia coli pgsA3 mutation, which causes deficiency in acidic phospholipids, leads to a significant accumulation of Sigma S. This accumulation is partly accounted for by the higher transcription level of rpoS; however, it has also been suggested that the cells accumulate Sigma S post-transcriptionally. We found that the level of the small regulatory RNA RprA, which is involved in the promotion of rpoS translation, is higher in pgsA3 cells than in pgsA+ cells. Induction of altered rpoS mRNA that does not depend on RprA in pgsA+ cells did not increase the level of Sigma S to the high level observed in pgsA3 cells, suggesting post-translational Sigma S accumulation in the latter. The mRNA levels of clpX and clpP, whose products form a ClpXP protease that degrades Sigma S, were much reduced in pgsA3 cells. Consistent with the reduced mRNA levels, the half-life of Sigma S in pgsA3 cells was much longer than in pgsA+ cells, indicating that downregulation of the degradation is a major cause for the high Sigma S content. We show that the downregulation can be partially attributed to activated CpxAR in the mutant cells, which causes repression of rpoE on whose gene product the expression of clpPX depends.

• 出版日期2010-6