Ubiquitin E3 ligase that acts as a crucial factor for crossing-over (CO) formation during meiosis. Essential for normal prophase I progression and for ensuring appropriate CO designation in meiosis. Recruits key components of the cross-over machinery either directly ou indirectly, leading to the activation of the MutL-gamma complex. The function of RNF212B in CO designation is dependent on its catalytic activity. . This is the function of Ensembl gene identifier ENSG00000215277 (RNF212B, ring finger protein 212B).