title: Bacteriophage GIL01 gp7 interacts with host LexA repressor to enhance DNA binding and inhibit RecA-mediated auto-cleavage.
abstract: The SOS response in Eubacteria is a global response to DNA damage and its activation is increasingly associated with the movement of mobile genetic elements. The temperate phage GIL01 is induced into lytic growth using the host's SOS response to genomic stress. LexA, the SOS transcription factor, represses bacteriophage transcription by binding to a set of SOS boxes in the lysogenic promoter P1. However, LexA is unable to efficiently repress GIL01 transcription unless the small phage-encoded protein gp7 is also present. We found that gp7 forms a stable complex with LexA that enhances LexA binding to phage and cellular SOS sites and interferes with RecA-mediated auto-cleavage of LexA, the key step in the initiation of the SOS response. Gp7 did not bind DNA, alone or when complexed with LexA. Our findings suggest that gp7 induces a LexA conformation that favors DNA binding but disfavors LexA auto-cleavage, thereby altering the dynamics of the cellular SOS response. This is the first account of an accessory factor interacting with LexA to regulate transcription.
authors.affiliation: Department of Biological and Environmental Science and Nanoscience Center, University of Jyvaskyla, Centre of Excellence in Biological Interactions, PO Box 35, F-40014 Jyvaskyla, Finland Instituto de Biología Molecular 'Eladio Viñuela' (CSIC), Centro de Biología Molecular 'Severo Ochoa' (CSIC-Universidad Autónoma de Madrid), Cantoblanco, 28049 Madrid, Spain nadine.fornelos@jyu.fi.
authors.forename: Nadine
authors.initials: N
authors.lastname: Fornelos
authors.affiliation: Department of Biology, Biotechnical Faculty, University of Ljubljana, Večna pot 111, 1000 Ljubljana, Slovenia.
authors.forename: Matej
authors.initials: M
authors.lastname: Butala
authors.affiliation: Department of Biology, Biotechnical Faculty, University of Ljubljana, Večna pot 111, 1000 Ljubljana, Slovenia.
authors.forename: Vesna
authors.initials: V
authors.lastname: Hodnik
authors.affiliation: Department of Biology, Biotechnical Faculty, University of Ljubljana, Večna pot 111, 1000 Ljubljana, Slovenia National Institute of Chemistry, Hajdrihova 19, 1000 Ljubljana, Slovenia.
authors.forename: Gregor
authors.initials: G
authors.lastname: Anderluh
authors.affiliation: Department of Biological and Environmental Science and Nanoscience Center, University of Jyvaskyla, Centre of Excellence in Biological Interactions, PO Box 35, F-40014 Jyvaskyla, Finland.
authors.forename: Jaana K
authors.initials: JK
authors.lastname: Bamford
authors.affiliation: Instituto de Biología Molecular 'Eladio Viñuela' (CSIC), Centro de Biología Molecular 'Severo Ochoa' (CSIC-Universidad Autónoma de Madrid), Cantoblanco, 28049 Madrid, Spain.
authors.forename: Margarita
authors.initials: M
authors.lastname: Salas
mesh_terms: D017103:Bacillus Phages / Q000235:genetics*; D001426:Bacterial Proteins / Q000378:metabolism*; D004247:DNA / Q000378:metabolism; D015967:Gene Expression Regulation, Viral; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D011938:Rec A Recombinases / Q000378:metabolism*; D012097:Repressor Proteins / Q000378:metabolism*; D013014:SOS Response, Genetics / Q000235:genetics*; D012697:Serine Endopeptidases / Q000378:metabolism*; D014158:Transcription, Genetic; D014764:Viral Proteins / Q000378:metabolism*; D000099160:LexA Repressor Protein
chemical_list: D001426:Bacterial Proteins; D004247:DNA; D011938:Rec A Recombinases; D012097:Repressor Proteins; D012697:Serine Endopeptidases; D014764:Viral Proteins; D000099160:LexA Repressor Protein