Catching a (Double-Strand) Break: The Rad51 and Dmc1 Strand Exchange Proteins Can Co-occupy Both Ends of a Meiotic DNA Double-Strand Break.

Amy J Macqueen,Michael Lichten

doi:10.1371/journal.pgen.1005741

Abstract

Catching a (Double-Strand) Break: The Rad51 and Dmc1 Strand Exchange Proteins Can Co-occupy Both Ends of a Meiotic DNA Double-Strand Break.

Highlights

The central task of meiosis poses an interesting challenge to recombination machinery, as its aim is to reinforce interactions between relatively distant homologous chromatids rather than spatially proximal sister chromatids. Both ends of a single broken DNA molecule must identify the same distant repair template but behave differently with respect to one another at the site of repair; the identification of single-end invasion (SEI) meiotic recombination intermediates in budding yeast [4] suggests that the ends of meiotic double-strand break (DSB) engage with a homologous template in a sequential fashion, as postulated in classic doublestrand break repair (DSBR) models [5]
Their super-resolution images reveal that Rad51 and Dmc1 assemble short filaments spanning only ~100 nt of single-stranded DNA (ssDNA) at meiotic DSB termini
Perhaps surprising given the capacity of RecA to form long filaments on ssDNA in vitro, the observations resonate well with recent single molecule studies that suggest RecA-mediated strand invasion occurs through discrete capture events involving just eight nucleotides of homology [22]

Summary

Introduction

Both ends of a single broken DNA molecule must identify the same distant repair template but behave differently with respect to one another at the site of repair; the identification of single-end invasion (SEI) meiotic recombination intermediates in budding yeast [4] suggests that the ends of meiotic DSBs engage with a homologous template in a sequential fashion, as postulated in classic doublestrand break repair (DSBR) models [5]. These Rad51-Dmc1 co-foci, observed in Arabidopsis [16], have been cited as evidence that Rad51 and Dmc1 load differentially on opposite ends of the meiotic DSB (Fig 1) [17,18].

Results

Conclusion