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. 1996 May;143(1):5–13. doi: 10.1093/genetics/143.1.5

Differential Suppression of Pria2::Kan Phenotypes in Escherichia Coli K-12 by Mutations in Pria, Lexa, and Dnac

S J Sandler 1, H S Samra 1, A J Clark 1
PMCID: PMC1207281  PMID: 8722757

Abstract

First identified as an essential component of the φX174 in vitro DNA replication system, PriA has ATPase, helicase, translocase, and primosome-assembly activities. priA1::kan strains of Escherichia coli are sensitive to UV irradiation, deficient in homologous recombination following transduction, and filamentous. priA2::kan strains have eightfold higher levels of uninduced SOS expression than wild type. We show that (1) priA1::kan strains have eightfold higher levels of uninduced SOS expression, (2) priA2::kan strains are UV(S) and Rec(-), (3) lexA3 suppresses the high basal levels of SOS expression of a priA2::kan strain, and (4) plasmid-encoded priA300 (K230R), a mutant allele retaining only the primosome-assembly activity of priA(+), restores both UV(R) and Rec(+) phenotypes to a priA2::kan strain. Finally, we have isolated 17 independent UV(R) Rec(+) revertants of priA2::kan strains that carry extragenic suppressors. All 17 map in the C-terminal half of the dnaC gene. DnaC loads the DnaB helicase onto DNA as a prelude for primosome assembly and DNA replication. We conclude that priA's primosome-assembly activity is essential for DNA repair and recombination and that the dnaC suppressor mutations allow these processes to occur in the absence of priA.

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Selected References

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