Fbxl19 recruits Rnf20 to CpG Islands and promotes H2B mono-ubiquitination [ChIP-Seq]

Rnf20 catalyzes lysine 120 mono-ubiquitination of histone H2B (H2Bub1) that has been previously invloved in normal differentiation of embryonic stem (ES) and adult stem cells. However,the mechanims underlying by which Rnf20 is recruited to its target chromosomal loci to generate H2Bub1 is still elusive. Here, we reveal that Fbxl19, a CxxC domain-containing protein, physically interacts with Rnf20, guides it preferentially to CpG island-containing target promoters, and thereby promotes mono-ubiqutination of H2B. We first show that up-regulation of Fbxl19 induces the level of global H2Bub1, while down-regulation of Fbxl19 reduces the level of H2Bub1 in mouse ES cells. Our genome-wide target mapping unveils the preferential occupancy of Fbxl19 on CpG island-containing promoters, and we further show that the binding of Fbxl19 is essential for the recruitment of Rnf20 to its target genes and subsequent H2Bub1. Altogether, our results demonstrate that Fbxl19 plays critical roles in the H2Bub1 pathway by recruiting Rnf20 to CGI target genes specifically and selectively. ChIP sequenicngs were performed for Fbxl19 and H2Bub1 in mouse ES cells. To perform Fbxl19 ChIP-seq we generated Fbxl19-overexpressing flag-biotin tagged clones and selected overexpression (OE)-high (more than 5 fold) and OE-low (sub-endogeous level) clones. Using these two OE-high and OE-low clones, we performed ChIP-seq of Fbxl19 using Streptavidin-conjugated beads. We also conducted H2Bub1 ChIP-seq under various conditions: normal, differentiation, Fbxl19-OE, Fbxl19-KD, and Fbxl19-KD under differentaiton conditions. Input was also sequenced and used for control.