RPA interacts with HIRA and regulates H3.3 deposition at gene regulatory elements in mammalian cells. Homo sapiens

The incorporation of histone variant H3.3 has been implicated in the formation and maintenance of specialized chromatin structure in metazoan cells. H3.3 is enriched in promoters, regulatory elements and genebody, and HIRA is required for H3.3 enrichment in these regions. But the mechanism of regulating H3.3 deposition by HIRA remains elusive. By screening a custom library of small hairpin RNAs (shRNAs) targeting known chromatin regulators, we identify single-stranded DNA binding protein RPA as being critically required for deposition of newly synthesized H3.3. RPA interacts with HIRA and H3.3 and co-localizes with HIRA at gene promoters and some regulatory elements across genome wide. Deletion of RPA dramatically reduces the enrichment of HIRA and newly synthesized H3.3 at these regions and reduced nascent anti-sense transcription. Taken together, our data demonstrate that RPA functions as new regulator of H3.3 deposition in promoter and some regulatory elements by recruiting HIRA and reveal a novel mechanism for RPA in chromatin and gene regulation. Overall design: We performed RPA1 and RPA2 ChIP-seq to find the RPA binding regions. mRNA-seq and BrU-seq were performed after shHIRA or shRPA1.