An Unusual Phage Repressor Encoded by Mycobacteriophage BPs.
Temperate bacteriophages express transcription repressors that maintain lysogeny by down-regulating lytic promoters and confer superinfection immunity. Repressor regulation is critical to the outcome of infection-lysogenic or lytic growth-as well as prophage induction into lytic replication. Mycobacteriophage BPs and its relatives use an unusual integration-dependent immunity system in which the phage attachment site (attP) is located within the repressor gene (33) such that site-specific integration leads to synthesis of a prophage-encoded product (gp33103) that is 33 residues shorter at its C-terminus than the virally-encoded protein (gp33136). However, the shorter form of the repressor (gp33103) is stable and active in repression of the early lytic promoter PR, whereas the longer virally-encoded form (gp33136) is inactive due to targeted degradation via a C-terminal ssrA-like tag. We show here that both forms of the repressor bind similarly to the 33-34 intergenic regulatory region, and that BPs gp33103 is a tetramer in solution. The BPs gp33103 repressor binds to five regulatory regions spanning the BPs genome, and regulates four promoters including the early lytic promoter, PR. BPs gp33103 has a complex pattern of DNA recognition in which a full operator binding site contains two half sites separated by a variable spacer, and BPs gp33103 induces a DNA bend at the full operator site but not a half site. The operator site structure is unusual in that one half site corresponds to a 12 bp palindrome identified previously, but the other half site is a highly variable variant of the palindrome.
Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania, 15260, United States of America.
Valerie M
VM
Villanueva
Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania, 15260, United States of America.
Lauren M
LM
Oldfield
Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania, 15260, United States of America.
Graham F
GF
Hatfull
D001483:Base Sequence; D018983:DNA Footprinting; D004279:DNA, Viral / Q000737:chemistry / Q000235:genetics; D008969:Molecular Sequence Data; D009160:Mycobacteriophages / Q000235:genetics* / Q000276:immunology; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D012097:Repressor Proteins / Q000235:genetics*; D014764:Viral Proteins / Q000737:chemistry / Q000235:genetics
D004279:DNA, Viral; D012097:Repressor Proteins; D014764:Viral Proteins