Meiotic recombination as a potential driver of short tandem repeat evolution
Sprache des Vortragstitels:
Mechanisms of Recombination
Sprache des Tagungstitel:
Meiotic recombination, a key biological process during germ cell production, is clustered in 0.5-2kb regions called recombination hotspots. The factors influencing the rapid sequence evolution observed in these hotspots are not well known yet, but the repair of double-strand breaks, required for the initiation of recombination, seems to play an important role in their sequence evolution. This could be either by biased transmission of GC alleles (GC-biased gene conversion, gBGC), or due to a higher frequency of de novo mutations at recombination hotspots. Short tandem repeats (STRs) probably also play an important role in hotspot evolution. In the last years, it has been shown that polymorphic STRs are enriched at recombination hotspots and several studies in E.coli and yeast identified STRs as drivers for recombination between plasmids. DSBs at recombination hotspots normally avoid poly-A tracts, but the deletion of 14 consecutive As within a mononucleotide run in the ARG4 hotspot in yeast leads to a reduction in recombination activity by 75%. Moreover, other studies have shown that length polymorphisms at STRs can lead to a reduction in recombination frequency, indicating that different types of STRs could either inhibit or decrease recombination, known as crossover refraction. Additionally, Drosophila studies showed an over-transmission of longer over shorter repeats, suggesting an insertion-biased gene conversion process similar to gBGC. These data suggests that recombination is able to influence the evolution of STRs and vice versa, but additional evidence is needed to obtain a more complete picture.