title: Antirepression system associated with the life cycle switch in the temperate podoviridae phage SPC32H.
abstract: Prophages switch from lysogenic to lytic mode in response to the host SOS response. The primary factor that governs this switch is a phage repressor, which is typically a host RecA-dependent autocleavable protein. Here, in an effort to reveal the mechanism underlying the phenotypic differences between the Salmonella temperate phages SPC32H and SPC32N, whose genome sequences differ by only two nucleotides, we identified a new class of Podoviridae phage lytic switch antirepressor that is structurally distinct from the previously reported Sipho- and Myoviridae phage antirepressors. The SPC32H repressor (Rep) is not cleaved by the SOS response but instead is inactivated by a small antirepressor (Ant), the expression of which is negatively controlled by host LexA. A single nucleotide mutation in the consensus sequence of the LexA-binding site, which overlaps with the ant promoter, results in constitutive Ant synthesis and consequently induces SPC32N to enter the lytic cycle. Numerous potential Ant homologues were identified in a variety of putative prophages and temperate Podoviridae phages, indicating that antirepressors may be widespread among temperate phages in the order Caudovirales to mediate a prudent prophage induction.
authors.affiliation: Department of Food and Animal Biotechnology, Department of Agricultural Biotechnology, Research Institute for Agriculture and Life Sciences, and Center for Food and Bioconvergence, Seoul National University, Seoul, South Korea.
authors.forename: Minsik
authors.initials: M
authors.lastname: Kim
authors.forename: Sangryeol
authors.initials: S
authors.lastname: Ryu
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism*; D001665:Binding Sites; D004279:DNA, Viral / Q000737:chemistry / Q000235:genetics; D015967:Gene Expression Regulation, Viral; D008969:Molecular Sequence Data; D017902:Podoviridae / Q000235:genetics* / Q000502:physiology; D011485:Protein Binding; D034741:RNA, Small Interfering / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D012483:Salmonella Phages / Q000235:genetics* / Q000502:physiology; D017422:Sequence Analysis, DNA; D012697:Serine Endopeptidases / Q000378:metabolism*; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism; D014779:Virus Replication; D000099160:LexA Repressor Protein
chemical_list: D001426:Bacterial Proteins; D004279:DNA, Viral; D034741:RNA, Small Interfering; D012097:Repressor Proteins; D012697:Serine Endopeptidases; D014764:Viral Proteins; D000099160:LexA Repressor Protein