Replication forks stalled at ultraviolet lesions are rescued via RecA and RuvABC protein-catalyzed disintegration in Escherichia coli.

ABSTRACT: Ultraviolet (UV) irradiation is not known to induce chromosomal fragmentation in sublethal doses, and yet UV irradiation causes genetic instability and cancer, suggesting that chromosomes are fragmented. Here we show that UV irradiation induces fragmentation in sublethal doses, but the broken chromosomes are repaired or degraded by RecBCD; therefore, to observe full fragmentation, RecBCD enzyme needs to be inactivated. Using quantitative pulsed field gel electrophoresis and sensitive DNA synthesis measurements, we investigated the mechanisms of UV radiation-induced chromosomal fragmentation in recBC mutants, comparing five existing models of DNA damage-induced fragmentation. We found that fragmentation depends on active DNA synthesis before, but not after, UV irradiation. At low UV irradia

SUBMITTER: Khan SR 

PROVIDER: S-EPMC3307332 | biostudies-literature | 2012 Feb

REPOSITORIES: biostudies-literature