Sister Cohesion and Structural Axis Components Mediate Homolog Bias of Meiotic Recombination

SummaryMeiotic double-strand break (DSB)-initiated recombination must occur between homologous maternal and paternal chromosomes (“homolog bias”), even though sister chromatids are present. Through physical recombination analyses, we show that sister cohesion, normally mediated by meiotic cohesin Rec8, promotes “sister bias”; that meiosis-specific axis components Red1/Mek1kinase counteract this effect, thereby satisfying an essential precondition for homolog bias; and that other components, probably recombinosome-related, directly ensure homolog partner selection. Later, Rec8 acts positively to ensure maintenance of bias. These complexities mirror opposing dictates for global sister cohesion versus local separation and differentiation of sisters at recombination sites. Our findings support DSB formation within axis-tethered recombinosomes containing both sisters and ensuing programmed sequential release of “first” and “second” DSB ends. First-end release would create a homology-searching “tentacle.” Rec8 and Red1/Mek1 also independently license recombinational progression and abundantly localize to different domains. These domains could comprise complementary environments that integrate inputs from DSB repair and mitotic chromosome morphogenesis into the complete meiotic program.

Graphical AbstractFigure optionsDownload high-quality image (285 K)Download as PowerPoint slideHighlights
► Meiotic axis proteins counteract cohesion to permit homolog bias establishment
► Meiotic cohesin Rec8 promotes homolog bias maintenance for crossover recombination
► Rec8 and Red1/Mek1 are independent progression brakes for normal recombination
► Tethered-loop axis recombinosomes form before recombination and contain both sisters