Cohesin complexes hold sister chromatids together during meiosis and mitosis but relatively little is known about the meiotic form of cohesin. Radhika Khetani and Sharon Bickel remedy this on p. 3123 by describing the localisation and dynamics of the cohesin subunits SMC1 and SMC3 during Drosophila oogenesis. They show that the SMCs colocalise with Orientation Disruptor (ORD), a protein needed for meiotic cohesion, at centromeres and along the arms of meiotic chromosomes during pachytene, where they form part of the chromosome cores (structures needed for homologous recombination at meiosis). In ord mutants, the SMCs do not accumulate at centromeres in oocytes but localise normally along chromosome cores during early meiosis, although the chromosome cores subsequently disassemble. The authors also show that chromosome core assembly but not recruitment of SMCs to the centromeres requires C(2)M, a meiosis-specific protein. Their data thus indicate that cohesin loading is regulated differently at centromeres and chromosome arms during meiosis.
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