Frameshift mutations in the bacteriophage Mu repressor gene can confer a trans-dominant virulent phenotype to the phage

Abstract

Virulent mutations in the bacteriophage Mu repressor gene were isolated and characterized. Recombination and DNA sequence analysis have revealed that virulence is due to unusual frameshift mutations which change several C-terminal amino acids. The vir mutations are in the same repressor region as the sts amber mutations which, by eliminating several C-terminal amino acids, suppress thermosensitivity of repressor binding to the operators by its N-terminal domain

The CRISPR/Cas Adaptive Immune System of Pseudomonas aeruginosa Mediates Resistance to Naturally Occurring and Engineered Phages

“…This lytic variant was made by deleting the nucleotides that encode the first 76 amino acids of the 185-amino-acid c repressor protein, which is required for lysogeny (13). A lytic phage similar to DMS3 that completely lacked its c repressor was previously isolated (17).…”

Control of Bacteriophage Mu Lysogenic Repression

“…Muvir phage induces the resident wild-type (WT) MucC or Mucts prophage by stimulating the degradation of the repressor synthesized by the prophage. [7][8][9] In both cases inactivation of the repressor is the physical cause of Mu induction. The cts and vir mutants thus exemplify two mechanisms of relieving repression of lysis genes by Rep: (i) lowering its affinity for the operators; or (ii) decreasing its intracellular concentration.…”

My life with Mu

“…RepcVir repressor mutants, for instance, are rapidly degraded by the host protease ClpXP. They communicate this instability to the wild type repressor, so that phages carrying the vir mutation not only grow on a Mu lysogen, but also induce a resident prophage because all repressor is degraded 19 ! While characterizing ClpXP as the protease involved, we realized that ClpX was also required for Mu growth.…”