INO80 requires a polycomb subunit to regulate the establishment of poised chromatin in murine spermatocytes [ChIP-seq]

INO80 is the catalytic subunit of the multi-subunit INO80-chromatin remodeling complex that has been implicated in DNA replication, repair, and transcription regulation. Ino80-deficiency in murine spermatocytes (Ino80cKO) results in pachytene arrest of spermatocytes, due to incomplete synapsis and aberrant DNA double-strand break repair (DSBR) that leads to apoptosis. We explored the mechanism by which INO80 mediates meiotic progression. RNA-seq on Ino80cKO spermatocytes revealed major changes in transcription, indicating that an aberrant transcription program arises upon INO80 depletion. In Ino80WTspermatocytes, genome-wide analysis showed that INO80-binding sites were mostly promoter proximal and necessary for the regulation of spermatogenic gene expression, primarily of premeiotic and meiotic genes. Further, most of the genes poised for activity, as well as those genes that are active, shared INO80 binding. In Ino80cKO spermatocytes, most poised genes demonstrated de-repression due to reduced H3K27me3 enrichment, and in turn showed increased expression levels. INO80 interacts with the core PRC2 complex member SUZ12 and promotes its recruitment. Further, INO80 mediates H2A.Z incorporation at the poised promoters, which was reduced in Ino80cKO spermatocytes. Taken together, INO80 is emerging as a major regulator of the meiotic transcription program by mediating poised chromatin establishment through SUZ12 binding. INO80 ChIPs were performed on spermatogenic cells isolated from Ino80WT mouse testis on P18. H2A.Z ChIPs were performed on spermatogenic cells obtained from Ino80WT and Ino80cKO (testis specific Ino80-deletion generated with Stra8-Cre) testes.