title: An SOS-inducible defective retronphage (phi R86) in Escherichia coli strain B.
abstract: In Escherichia coli, RecA protein regulates the DNA damage-inducible survival-enhancing SOS response. Mutant allele recA730, which causes constitutive SOS expression, is lethal at high temperatures in B/r, a derivative of wild-type B, but not in K-12 or in certain B/r--K-12 hybrids. We present evidence that killing is due to SOS induction of a defective retronphage, phi R86, which is integrated into the B/r chromosome at 19 min, but is absent in K-12. phi R86 contains retron EC-86 which encodes reverse transcriptase and a small multicopy DNA-RNA complex, msDNA-RNA. Induction of phi R86 in recA730 B/r strains results in inhibition of host DNA replication before cell death. A retronphage 'killer' gene, ORF336, when overexpressed from a plasmid, causes similar effects without SOS induction. phi R86 is not detectably u.v.-inducible in recA+ strains.
mesh_terms: D003090:Coliphages / Q000235:genetics / Q000502:physiology*; D004269:DNA, Bacterial / Q000096:biosynthesis; D004277:DNA, Single-Stranded / Q000235:genetics / Q000378:metabolism; D003673:Defective Viruses / Q000235:genetics / Q000502:physiology; D004926:Escherichia coli / Q000235:genetics / Q000502:physiology*; D016366:Open Reading Frames; D012329:RNA, Bacterial / Q000235:genetics / Q000378:metabolism; D012194:RNA-Directed DNA Polymerase / Q000235:genetics; D011938:Rec A Recombinases / Q000378:metabolism*; D013014:SOS Response, Genetics; D013696:Temperature; D014466:Ultraviolet Rays; D010948:Viral Plaque Assay; D014775:Virus Activation
chemical_list: D004269:DNA, Bacterial; D004277:DNA, Single-Stranded; D012329:RNA, Bacterial; C058681:msDNA; D011938:Rec A Recombinases; D012194:RNA-Directed DNA Polymerase