HIRA Complex Presets Transcriptional Potential Through Coordinating Depositions Of The Histone Variants H3.3 And H2A.Z On Genome In MESCs

In eukaryotic cells,genomic DNA is packaged into a high-order structure known as chromatin in the nucleus.The exchange of histones alters chromatin compaction degree and participates in many cellular processes such as transcription regulation,DNA repair,assembly of 30 nm chromatin fiber and idiochromosome condensation.As the most conserved histone variants among different species,H3.3 and H2 A.Z act actively in the regulation processes of chromatin dynamics and gene transcription.In previous studies,it's well known that H3.3 makes the chromatin structure loose whereas H2 A.Z contributes to the chromatin compaction.HIRA complex act as the chaperone of H3.3 responsible for H3.3 recruitment to actively transcribed regions.SRCAP complex is an important chromatin remodeler which is implicated in H2 A.Z enrichment on genome.However,the correlation between H2 A.Z and H3.3 is still unclear.To better understand the mechanism,we mapped anti-H2 A.Z Ch IP-seq data on genome-wide in mouse embryonic stem cells.The enrichment of H2 A.Z is reduced significantly,especially at promoters,due to HIRA complex defect in H3.3 dependent or independent manner.In vivo and in vitro biochemical assays show the interaction between HIRA and SRCAP complex,which indicates that HIRA complex regulates H2 A.Z distribution via SRCAP complex.Then we performed CUT&Tag assay to monitor the distribution of SRCAP and HIRA on genome wide.The analysis shows that a significant portion of HIRA colocalize with SRCAP.HIRA complex deletion reduces the enrichment of SRCAP,which further impacts the recruitment of H2 A.Z.Further analyses of GST-MNase-seq and ATAC-seq clarified HIRA complex characterized high-order chromatin around TSSs to preset the t RA induced transcriptional activation.This cooperation between histone variants and chaperones mediated chromatic accessibility and transcriptional potential.HIRA complex deletion leads to ineffective differentiation of NPC and disordered expression of relative genes.In addition,HIRA complex delation impacts expression levels of a series DNMTs,along with dramatic reduction of DNA methylation on genome wide.To sum up,HIRA complex,the chaperone of H3.3,mediates H2 A.Z deposition through coordinating with SRCAP complex to preset transcriptional potential during differentiation.