Crossing-over between homologous chromosomes is essential for accurate segregation during meiosis. In mammals, factors required for crossing over include RNF212 and HEI10, RING-finger domain proteins implicated in modification by SUMO and ubiquitin, respectively. Here we show that a third RING protein, RNF212B, is essential for crossing over in mouse and characterize its relationships with RNF212 and HEI10. Mutant analysis indicates that, analogous to RNF212, RNF212B regulates recombination occurring in the context of synapsed chromosomes by stabilizing pro-crossover factors, regulating the progression of recombination, and enabling the differentiation and maturation of crossover-specific recombination complexes. Also, like RNF212, RNF212B localizes between synapsed chromosomes, initially as numerous foci along synaptonemal complexes (SCs) before undergoing HEI10-dependent redistribution to accumulate at prospective crossover sites. Despite these similarities, accumulation of RNF212B at nascent crossover sites is much greater than RNF212 and occurs earlier, coincident with the appearance of HEI10 foci, implicating concerted action of RNF212B and HEI10 in the differentiation of crossover sites. RNF212B localization also shows greater dependence on DNA double-strand breaks and SC formation than RNF212. Together, our analysis delineates three distinct but interdependent RING proteins that regulate meiotic recombination by integrating signals from DSBs, synapsis, the cell-cycle, and developing crossover sites.

Distinct and interdependent functions of three RING proteins regulate recombination during mammalian meiosis

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