Study of Ren, RexA, and RexB Functions Provides Insight Into the Complex Interaction Between Bacteriophage ? and Its Host, Escherichia coli

The phage ? rexA and rexB genes are expressed from the P RM promoter in ? lysogens along with the cI repressor gene. RexB is also expressed from a second promoter, P LIT, embedded in rexA. The combined expression of rexA and rexB causes Escherichia coli to be more ultraviolet (UV) sensitive. Sensitivity is further increased when RexB levels are reduced by a defect in the P LIT promoter, thus the degree of sensitivity can be modulated by the ratio of RexA/RexB. Expression of the phage ? ren gene rescues this host UV sensitive phenotype; Ren also rescues an aberrant lysis phenotype caused by RexA and RexB. We screened an E. coli two-hybrid library to identify bacterial proteins with which each of these phage proteins physically interact. The results extend previous observations concerning ? Rex exclusion and show the importance of E. coli electron transport and sulfur assimilation pathways for the phage.

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