Hotspots of homologous recombination.
Homologous recombination occurs at higher than average frequency at and near hotspots. Hotspots are special nucleotide sequences recognized by proteins that promote, directly or indirectly, a rate limiting step of recombination. This review focuses on two well-studied examples, the Chi sites of the bacterium Escherichia coli and the M26 site of the fission yeast Schizosaccharomyces pombe. Chi, 5' G-C-T-G-G-T-G-G 3', is recognized by the RecBCD enzyme, which nicks the DNA near Chi and produces a 3'-ended single-stranded DNA 'tail'; this tail is a potent substrate for homologous pairing by RecA and single-stranded DNA binding proteins. M26, 5' A-T-G-A-C-G-T 3', is recognized by a heterodimeric protein and stimulates, by an as-yet-unknown mechanism, meiotic recombination at and near the ade6 gene. Additional hotspots in bacteria, fungi, and mammals enhance recombination directly or indirectly via a variety of mechanisms. Although hotspots are widespread among organisms, the biological role of their localized enhancement of recombination remains a matter of speculation.
Smith
G R
GR
Fred Hutchinson Cancer Research Center, Seattle, Washington 98104.
D001665:Binding Sites; D004926:Escherichia coli / Q000235:genetics*; D043211:Exodeoxyribonuclease V; D005090:Exodeoxyribonucleases / Q000378:metabolism*; D011995:Recombination, Genetic; D012045:Regulatory Sequences, Nucleic Acid; D012568:Schizosaccharomyces / Q000235:genetics*
D005090:Exodeoxyribonucleases; D043211:Exodeoxyribonuclease V