Recombinational Repair of DNA Damage in Escherichia coli and Bacteriophage λ

Abstract

SUMMARY Although homologous recombination and DNA repair phenomena in bacteria were initially extensively studied without regard to any relationship between the two, it is now appreciated that DNA repair and homologous recombination are related through DNA replication. In Escherichia coli, two-strand DNA damage, generated mostly during replication on a template DNA containing one-strand damage, is repaired by recombination with a homologous intact duplex, usually the sister chromosome. The two major types of two-strand DNA lesions are channeled into two distinct pathways of recombinational repair: daughter-strand gaps are closed by the RecF pathway, while disintegrated replication forks are reestablished by the RecBCD pathway. The phage λ recombination system is simpler in that its major reaction is to link two double-stranded DNA ends by using overlapping homologous sequences. The remarkable progress in understanding the mechanisms of recombinational repair in E. coli over the last decade is due to the in vitro characterization of the activities of individual recombination proteins. Putting our knowledge about recombinational repair in the broader context of DNA replication will guide future experimentation.

EXTENSIVE VARIATION IN NATURAL COMPETENCE INHAEMOPHILUS INFLUENZAE

“…Survival of incoming DNA requires the products of the competence genes dprA and comM, which appear to protect DNA from cellular nucleases (Karudapuram et al 1995;Gwinn et al 1998;Berge et al 2003;Mortier-Barriere et al 2007). Recombination of incoming DNA in H. influenzae is known to depend on the actions of the recombinational repair protein Rec-1 (RecA homolog); the genome also contains homologs of many other proteins known to affect recombination (Kuzminov 1999). Mutations affecting these activities could thus be responsible for discrepancies between DNA uptake and transformation.…”

Crystal structure and mutational study of RecOR provide insight into its mode of DNA binding

“…Homologous recombination, in addition to its fundamental role in genetic diversification of bacterial genomes, plays an essential role in the repair of a variety of DNA damage, including double-strand breaks (Kuzminov, 1999;Michel et al, 2004). In Escherichia coli, the initiation of homologous recombination can be carried out by either the RecBCD or the RecFOR proteins; in both cases, these proteins act as mediators for RecA binding to single-stranded DNA (ssDNA) to allow for homologous strand invasion (Kowalczykowski et al, 1994).…”

Roles for replichores and macrodomains in segregation of the Escherichia coli chromosome

“…The RecBCD complexes, which process double-strand breaks during their repair, recognize a skewed octamer termed Chi. This is thought to favour recombinational repair of breaks occurring behind replication forks (Kuzminov, 1999;Gruss & Michel, 2001). A second function of replichore organization has been suggested in the resolution of chromosome dimers (Corre et al, 2000;Pérals et al, 2000;Lobry & Louarn, 2003).…”