Identification and molecular characterization of the mammalian α-kleisin RAD21L

Meiosis is a fundamental process that generates new combinations between maternal and paternal genomes and haploid gametes from diploid progenitors. Many of the meiosis-specific events stem from the behavior of the cohesin complex (CC), a proteinaceous ring structure that entraps sister chromatids until the onset of anaphase. CCs ensure chromosome segregation, participate in DNA repair, regulate gene expression, and also contribute to synaptonemal complex (SC) formation at meiosis by keeping long-range distant DNA interactions through its conserved structure. Studies from yeast to humans have led to the assumption that Scc1/RAD21 is the alpha-kleisin that closes the tripartite CC that entraps two DNA molecules in mitosis, while its paralog REC8 is essential for meiosis. Here we describe the identification of RAD21L, a novel mammalian CC subunit with homology to the RAD21/REC8 alpha-kleisin subfamily, which is expressed in mouse testis. RAD21L interacts with other cohesin subunits such as SMC1 alpha, SMC1 beta, SMC3 and with the meiosis-specific STAG3 protein. Thus, our results demonstrate the existence of a new meiotic-specific CC constituted by this alpha-kleisin and expand the view of REC8 as the only specific meiotic alpha-kleisin.