PIASy overexpression effects on gene expression in mouse 2-cell embryos

During the maternal-to-zygotic transition (MZT), maternal mRNAs and proteins are degraded, and zygotic genes are activated. We have previously shown that the ubiquitin-proteasome system (UPS) after fertilization plays a role in onset of zygotic transcription. However, the maternal proteins, which are degraded by UPS and can contribute to the zygotic transcription, have not been identified. Here, we identified PIASy (Protein inhibitor of activated STAT y), which is an E3 SUMO ligase, as the maternal proteins that were degraded via UPS after fertilization and by examining the overexpression of PIASy. We observed developmental arrest at the mouse 2-cell stage. Therefore, we examined the effect of PIASy overexpression on zygotic gene expression by using the RNA-sequencing analysis. Overall design: Total RNA-seq was performed using (1) PIASy-WT, (2) PIASy-C335F (SUMO ligase mutant) overexpressed mouse 2-cell embryos, and (3) non-injected mouse 2-cell embryos, in duplicates.