Lethality of the double mutations rho rep and rho ssb in Escherichia coli

Abstract

The similarity of rho mutants to rep and ssb mutants in sensitivity to UV light and in recombination deficiency suggested that the function of the Rho protein might be related to that of Rep and Ssb. In support of that idea, we found that rho rep and rho ssb double mutants are either nonviable, or at best only marginally viable. Viability could be restored by suppressor mutations, one of which mapped either in the rho gene or close to its 5'-end. Rho may thus share a role with Rep and Ssb in replication and the structural maintenance of DNA; a multifunctional Rho protein could account for the diversity of the defects seen in rho mutants, some of which appear to have no relation to the defect in transcription termination.

The single-stranded DNA-binding protein of Escherichia coli.

“…The helicase activity of helicase II is also known to be stimulated by SSB (245). Fassler et al (111) have shown that rho ssb-113 double-mutation combinations are lethal, indicating a possible interaction of Rho and SSB. Further indirect evidence for protein-protein interactions has come from studies of extragenic suppressors to ssb mutations (260,325).…”

Lethality of rep recB and rep recC double mutants of Escherichia coli

“…rep mutations in combination with uvrD and rho mutations make ceils non-viable (Taucher-Sholtz et aL, 1983;Fassler et aL, 1985;Washburn and Kushner, 1991). UvrD is involved in repair of mismatches and u.v.…”

Escherichia coli repgene: sequence of the gene, the encoded helicase, and its homology withuvrD*

“…coli that have defects in both the rep gene and either rho, or uvrD, or ssb (9,10). In the case of uvrD, which encodes DNA helicase II (9,(11)(12)(13), it is reasonable to postulate that one of the two helicases, Rep or helicase II, is required for an essential cell function.…”