GSE118827
Sodium arsenite exposure inhibits histone acetyltransferase p300 for attenuating H3K27ac at enhancers in mouse embryonic fibroblast cells
Both epidemiological investigations and animal studies have linked arsenic-contaminated water to cancers, in- cluding skin, liver and lung cancers. Besides genotoxicity, arsenic exposure-related pathogenesis of disease is widely considered through epigenetic mechanisms; however, the underlying mechanism remains to be deter- mined. Herein we explore the initial epigenetic changes via acute sodium arsenite (As) exposures of mouse em- bryonic fibroblast (MEF) cells and histone H3K79 methyltransferase Dot1L knockout (Dot1L-? /-) MEF cells. Our RNA-seq and Western blot data demonstrated that, in both cell lines, acute As exposure abolished histone acetyl- transferase p300 at the RNA level and subsequent protein level. Consequently, p300-specific main target histone H3K27ac, a marker separating active from poised enhancers, decreased dramatically as validated by both West- ern blot and ChIP-qPCR/seq analyses. Concomitantly, H3K4me1 as another well-known marker for enhancers also showed significant decreases, suggesting an underappreciated crosstalk between H3K4me1 and H3K27ac involved in As exposure. Significantly, As exposure-reduced H3K27ac and H3K4me1 inhibited the expression of genes including EP300 itself and Kruppel Like Factor 4(Klf4) that both are tumor suppressor genes. Collectively, our investigations identified p300 as an internal bridging factor within cells to sense external environmental As exposure to alter chromatin, thereby changing gene transcription for disease pathogenesis. Overall design: RNA-seq were performed for the control and low dose As treated MEF cell and Dot1L mutant to explore the  whole genome wide transcriptional response to the low dose As. In addition, we also investigated changes in histone mark  H3K27ac occupancy at the MEF and As treated MEF cells to see the histone change at the enhancer or promoter reigions of the differentially expressed genes.