Protein kinase N1 mediates phosphorylation of H3.3 serine 31 for rapid gene activation (ATAC-Seq II)
Atherosclerosis, which develops in the inner layer of arteries, is the major cause of myocardial infarction and stroke. Atherosclerotic plaques develop preferentially in arterial regions exposed to disturbed blood flow, such as vessel curvatures, bifurcations and branching points, where endothelial cells develop an inflammatory phenotype. How disturbed flow induces endothelial cell inflammation is incompletely understood. We show here that histone H3.3 phosphorylation at serine 31 (H3.3S31) plays a critical role in disturbed flow-induced endothelial inflammation, as it allows the rapid induction of FOS and FOSB, which are required for disturbed flow-induced inflammatory gene expression. We identified protein kinase N1 (PKN1) as the kinase responsible for disturbed flow-induced H3.3S31 phosphorylation. PKN1 becomes activated by disturbed flow in an integrin a5b1-dependent manner and then translocates to the cell nucleus. We found that PKN1 is also involved in the phosphorylation of the AP-1 transcription factor JUN. Mice with endothelium-specific loss of PKN1 or endothelial expression of S31 phosphorylation-deficient mutants of H.3.3 show reduced endothelial inflammation and disturbed flow-induced vascular remodeling in vitro and in vivo. Our data identify a novel mechanism of H3.3S31 phosphorylation which may serve as a target for preventive and therapeutic anti-atherosclerotic strategies. Overall design: In order to identify early changes in endothelial chromatin accessibility induced by disturbed flow, we performed the Assay of Transposase-Accessible Chromatin coupled to high-throughput sequencing (ATAC-Seq) in human umbilical artery endothelial cells (HUAECs) exposed to disturbed flow.