A bacterial G protein-mediated response to replication arrest.
To define factors in E. coli promoting survival to replication fork stress, we isolated insertion mutants sensitive to replication inhibitors. One insertion caused partial loss of the universally conserved GTPase, obgE/yhbZ gene. Although obgE is essential for growth, our insertion allele supported viability until challenged with various replication inhibitors. A mutation designed to negate the GTPase activity of the protein produced similar phenotypes, but was genetically dominant. Synergistic genetic interactions with recA and recB suggested that chromosome breaks and regressed forks accumulate in obgE mutants. Mutants in obgE also exhibited asynchronous overreplication during normal growth, as revealed by flow cytometry. ObgE overexpression caused SeqA foci, normally localized to replication forks, to spread extensively within the cell. We propose that ObgE defines a pathway analogous to the replication checkpoint response of eukaryotes and acts in a complementary way to the RecA-dependent SOS response to promote bacterial cell survival to replication fork arrest.
Foti
James J
JJ
Department of Biology and Rosenstiel Basic Medical Sciences Research Center, Brandeis University, Waltham, MA 02454-9110, USA.
Schienda
Jaclyn
J
Sutera
Vincent A
VA
Lovett
Susan T
ST
D000251:Adenosine Triphosphatases / Q000378:metabolism; D002470:Cell Survival; D019457:Chromosome Breakage; D002876:Chromosomes, Bacterial / Q000502:physiology; D004265:DNA Helicases / Q000378:metabolism; D004261:DNA Replication; D004926:Escherichia coli / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D043211:Exodeoxyribonuclease V / Q000378:metabolism; D005434:Flow Cytometry; D020558:GTP Phosphohydrolases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D005799:Genes, Dominant; D020559:Monomeric GTP-Binding Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D016254:Mutagenesis, Insertional; D009154:Mutation; D010641:Phenotype
D029968:Escherichia coli Proteins; D043211:Exodeoxyribonuclease V; C468322:exodeoxyribonuclease V, E coli; D000251:Adenosine Triphosphatases; D020558:GTP Phosphohydrolases; C491572:ObgE protein, E coli; D004265:DNA Helicases; D020559:Monomeric GTP-Binding Proteins