LexA cleavage is required for CTX prophage induction

摘要

The physiologic conditions and molecular interactions that control phage production have been studied in few temperate phages. We investigated the mechanisms that regulate production of CTXphi, a temperate filamentous phage that infects Vibrio cholerae and encodes cholera toxin. In CTXphi lysogens, the activity of P-rstA the only CTXphi P promoter required for CTX prophage development, is repressed by RstR, the CTXphi repressor. We found that the V. cholerae SOS response regulates CTXphi production. The molecular mechanism by which this cellular response to DNA damage controls CTXphi production differs from that by which the E coli SOS response controls induction of many prophages. UV-stimulated CTXphi production required RecA-dependent autocleavage of LexA, a repressor that controls expression of numerous host DNA repair genes. LexA and RstR both bind to and repress P-rstA.Thus, CTXphi production is controlled by a cellular repressor whose activity is regulated by the cell's response to DNA damage.