H2A monoubiquitination targeting by cohesi n subunits in Arabidopsis

Histone H2A monoubiquitination (H2Aub1) is a ubiquitous and conserved post-translational modification, playing a non-degradative role in multiple progresses including transcription regulation. In Arabidopsis thaliana, H2Aub1 is mediated by AtRING1s and AtBMI1s, catalytic subunits of Polycomb repressive complex 1 (PRC1). Despite PRC2-associated repressive role of H2Aub1, the mechanism regarding how H2Aub1 distributed on non-H3K27me3 region need to be explained. In this article, we show that the two cohesin subunits AtSCC3 and AtSYN4 directly interact with AtBMI1A/B/C, and theH2Aub1 levels are significantly reduced in atsyn4orAtSCC3RNAi plants. By ChIP-seq analysis, we found that AtSYN4 and AtSCC3 co-localize with H2Aub1 in genome, and are related to H3K27me3-independent transcription activation. Further, we provide evidences to show that AtSYN4 directly bind to G-box element and regulate H2Aub1 modification in G-box containing loci. These findings reveal that AtSCC3 and AtSYN4 are directly and functionally associated with AtBMI1s. Our study uncovers the mechanism of H2Aub1 targeting modification. Overall design: The 7-day-old whole seedlings of wild type (WT) were sequenced.