A non-hypervariable human minisatellite strongly stimulates in vitro intramolecular homologous recombination

Several features indicate that the low polymorphic human minisatellite MsH42 region could be involved in recombination. It contains different well-known recombination motifs, is able to generate single-stranded loops and is specifically recognized by nuclear proteins. These characteristics led us to investigate the possible recombinogenic activity of the MsH42 region in terms of intramolecular recombination. We constructed two plasmids, one of them carrying two copies of the minisatellite region and the other one containing sequences upstream of this repetitive region. We showed that MsH42 strongly stimulates intramolecular in vitro recombination, approximately 22 times more than the control sequence, solely when the source of biological extract is mouse testes, suggesting that MsH42 could be a hotspot involved in meiotic recombination. Furthermore, there is a direct relationship between the frequency of equal crossovers and the enhancement of recombination. Interestingly, the third repeat of the minisatellite array is always involved in the resolution of unequal crossovers leading to minisatellite shortening. As far as we know, our results provide the first evidence that a non-hypervariable minisatellite can enhance homologous recombination.