Ga. Cromie et Drf. Leach, Recombinational repair of chromosomal DNA double-strand breaks generated by a restriction endonuclease, MOL MICROB, 41(4), 2001, pp. 873-883
DNA double-strand break repair can be accomplished by homologous recombinat
ion when a sister chromatid or a homologous chromosome is available. Howeve
r, the study of sister chromatid double-strand break repair in prokaryotes
is complicated by the difficulty in targeting a break to only one copy of t
wo essentially identical DNA sequences. We have developed a system using th
e Escherichia coli chromosome and the restriction enzyme EcoKI, in which do
uble-strand breaks can be introduced into only one sister chromatid. We hav
e shown that the components of the RecBCD and RecFOR 'pathways' are require
d for the recombinational repair of these breaks. Furthermore, we have show
n a requirement for SbcCD, the prokaryotic homologue of Rad50/Mre11. This i
s the first demonstration that, like Rad50/Mre11, SbcCD is required for rec
ombination in a wild-type cell. Our work suggests that the SbcCD-Rad50/Mre1
1 family of proteins, which have two globular domains separated by a long c
oiled-coil linker, is specifically required for the co-ordination of double
-strand break repair reactions in which two DNA ends are required to recomb
ine at one target site.