The RecBC enzyme loads RecA protein onto ssDNA asymmetrically and independently of chi, resulting in constitutive recombination activation.
Double-strand DNA break repair and homologous recombination in Escherichia coli proceed by the RecBCD pathway, which is regulated by cis-acting elements known as chi sites. A crucial feature of this regulation is the RecBCD enzyme-directed loading of RecA protein specifically onto the 3'-terminal, chi-containing DNA strand. Here we show that RecBC enzyme (lacking the RecD subunit) loads RecA protein constitutively onto the 3'-terminal DNA strand, with no requirement for chi. This strand is preferentially utilized in homologous pairing reactions. We propose that RecA protein loading is a latent property of the RecBCD holoenzyme, which is normally blocked by the RecD subunit and is revealed following interaction with chi.
Churchill
J J
JJ
Biochemistry and Molecular Biology Graduate Group, University of California, Davis, California 95616-8665 USA.
Anderson
D G
DG
Kowalczykowski
S C
SC
D015139:Blotting, Southern; D004260:DNA Repair; D004277:DNA, Single-Stranded / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics; D029968:Escherichia coli Proteins; D043211:Exodeoxyribonuclease V; D005090:Exodeoxyribonucleases / Q000378:metabolism*; D005798:Genes, Bacterial; D008957:Models, Genetic; D015345:Oligonucleotide Probes; D011938:Rec A Recombinases / Q000378:metabolism*; D011995:Recombination, Genetic; D013997:Time Factors
D004277:DNA, Single-Stranded; D029968:Escherichia coli Proteins; D015345:Oligonucleotide Probes; D011938:Rec A Recombinases; D005090:Exodeoxyribonucleases; C028450:exodeoxyribonuclease I; D043211:Exodeoxyribonuclease V; C468322:exodeoxyribonuclease V, E coli