Human Rad51 protein displays enhanced homologous pairing of DNA sequences resembling those at genetically unstable loci

摘要

DNA strand exchange, the central step of homologous recombination, is considered to occur approximately independently of DNA sequence content. However, certain prokaryotic and eukaryotic genomic loci display either an enhanced or reduced frequency ofgenetic exchange. Here we show that the Homo sapiens DNA strand exchange protein, HsRad51, shows a preference for binding to single-stranded DNA sequences primarily rich in G-residues and poor in A- and C-residues, and that these DNA sequences manifest enhanced HsRad51 protein-dependent homologous pairing. Both of these properties are common to all DNA strand exchange proteins examined thus far. These preferred DNA pairing sequences resemble those found at genetic loci in human cells that cause genomicinstability and lead to genetic diseases.