USP16-mediated Histone H2A Lysine-119 Deubiquitination during Oocyte Maturation is a Prerequisite for Zygotic Genome Activation

Maternal-to-zygotic transition (MZT) is the first and key step in the control of animal development and is intimately related to changes of chromatin structure and histone modifications. Mono-ubiquitination of histone H2A at lysine-119 (H2AK119ub1), an important epigenetic modification in regulating chromatin configuration and function, is primarily catalyzed by polycomb repressive complex 1 (PRC1) and contributes to resistance to transcriptional reprogramming in mouse embryos. In this study, the genome-wide dynamic distribution of H2AK119ub1 during MZT in mice was investigated by chromosome immunoprecipitation and sequencing. The results indicated that H2AK119ub1 accumulated in fully grown oocytes, enriched at the transcriptional start sequences (TSSs) of maternal genes, but was promptly removed after meiotic resumption, particularly at the TSSs of early zygotic genes, by a previously unidentified mechanism. Genetic evidences indicated that ubiquitin-specific peptidase 16 (USP16) is the major deubiquitinase of H2AK119ub1 in mouse oocytes. Conditional knockout of Usp16 in oocytes did not impair their survival, growth, andor meiotic maturation. However, oocytes lacking USP16 were unable to undergo zygotic genome activation or gain developmental competence after fertilization, due to high levels of H2AK119ub1 deposition on the zygotic genomes. Taken together, this study indicates that H2AK119ub1 is erased during oocyte maturation by an USP16-dependent mechanism, which ensures zygotic genome reprogramming and transcriptional activation of essential early zygotic genes. Overall design: WT oocytes at GV and MII stages, WT Zygotes, WT 2-cell stage embryos are collected to perform H2AK119ub1 ChIP sequencing. WT and Usp16 cKO embryos at zygote and 2-cell stages for two replicates are performed RNA sequencing.