PHF7 Links H3K4 Methylation to H2A Ubiquitination During Spermiongenesis

Histone ubiquitination has been suggested to serve as a “tag” for nucleosome removal during histone-to-protamine exchange that is essential for chromatin packaging in round spermatids. Here, we screen for putative E3 ligase and identify that the PHF7, containing both RING finger and PHD domains, is critical for H2A ubiquitination and histone removal. Mechanistically, its PHD domain as a histone code reader can specifically bind H3K4me3/me2 and its RING domain as a histone writer can ubiquinate H2A. So we want to use ChIP-seq to see whether all PHF7-binding peaks overlapped with those of H3K4me3. We report the application of ChIP-seq for high-throughput profiling of histone modifications in spermatids. By obtaining over 240M of sequences from chromatin immunoprecipitated DNA, we generated genome-wide chromatin-state maps and PHF7 binding position of late spermatids. We find binding peaks of PHF7, H3K4me3 and ub-H2A were mainly enriched at gene-regulatory elements (-5kb to +5kb from transcriptional start site), including promoter and enhancers, indicative of important roles in gene regulations. More than 96% (n=15419) of all PHF7-binding peaks overlapped with those of H3K4me3, supporting a specific binding of PHF7 to H3k4me3. Moreover, the common binding sites between PHF7 and H3K4me3 were associated with ub-H2A. Taken together, these results demonstrate that PHF7 ubiquitinate H2A through binding with H3K4me3. Examination of different histone modifications (H3K4me3 and ub-H2A) and PHF7 binding in late spermatids. We isolated late spermatids from testes of Phf7-KI-flag mice according to reported protocol (Bastos et al., 2005) as different sample for downsrream analysis.