Histone acetyltransferase 7 (KAT7)-dependent intragenic histone acetylation regulates endothelial cell gene regulation.

Although the functional role of chromatin marks at promoters in mediating cell-restricted gene expression has been well characterized, the role of intragenic chromatin marks is not well understood, especially in endothelial cell (EC) gene expression. Here, we characterized the histone H3 and H4 acetylation profiles of 19 genes with EC-enriched expression via locus-wide chromatin immunoprecipitation followed by ultra-high-resolution (5 bp) tiling array analysis in ECs versus non-ECs throughout their genomic loci. Importantly, these genes exhibit differential EC enrichment of H3 and H4 acetylation in their promoter in ECs versus non-ECs. Interestingly, VEGFR-2 and VEGFR-1 show EC-enriched acetylation across broad intragenic regions and are up-regulated in non-ECs by histone deacetylase inhibition. It is unclear which histone acetyltransferases (KATs) are key to EC physiology. Depletion of KAT7 reduced VEGFR-2 expression and disrupted angiogenic potential. Microarray analysis of KAT7-depleted ECs identified 263 differentially regulated genes, many of which are key for growth and angiogenic potential. KAT7 inhibition in zebrafish embryos disrupted vessel formation and caused loss of circulatory integrity, especially hemorrhage, all of which were rescued with human KAT7. Notably, perturbed EC-enriched gene expression, especially the VEGFR-2 homologs, contributed to these vascular defects. Mechanistically, KAT7 participates in VEGFR-2 transcription by mediating RNA polymerase II binding, H3 lysine 14, and H4 acetylation in its intragenic region. Collectively, our findings support the importance of differential histone acetylation at both promoter and intragenic regions of EC genes and reveal a previously underappreciated role of KAT7 and intragenic histone acetylation in regulating VEGFR-2 and endothelial function.

[Effect of epidermal growth factor on expression of cell cycle-regulatory proteins and proliferation of rabbit corneal epithelial cells].

OBJECTIVE: To investigate the effects of epidermal growth factor (EGF) on the proliferation of cultured rabbit corneal epithelial (RCE) cells and the expression of cell cycle-regulatory proteins in these cells. METHODS: It was an experimental study. Cultured RCE cells were exposed to EGF at different concentrations (0, 1, 5, 10, 25 and 50 microg/L) and different time (0, 2, 4, 6, 8 and 10 days). Cell morphologic changes were observed under a phase contrast microscope. Cell proliferation was measured using the WST-1 cell proliferation assay. The expression of cell cycle-regulatory proteins, cyclinD1, CDK4, p27, p21 and p18, was examined using Western blot analysis. The data was statistically analyzed with SPSS 11.5 software, difference between two groups and multiple groups was compared by t test and ANOVA, respectively. RESULTS: Treatment with EGF did not obviously change the cell morphology. EGF significantly induced the proliferation of RCE cells in a dose- and time-dependent manner. In cells treated with different concentrations of EGF, the proliferation rate of 5, 10, 25 and 50 microg/L EGF group at 72 h were 9.0%, 23.5%, 20.8% and 17.7%, respectively. The difference was statistically significant as compared with the control group (F = 45.48, P < 0.01). EGF at 10 microg/L showed maximally stimulating effect. After EGF treatment for 0, 24, 48 and 72 h, the expression of cyclinD1 and CDK4 proteins was markedly increased (cyclinD1/beta-actin ratio was 0.253, 0.591, 0.885 and 1.043; CDK4/beta-actin ratio was 0.422, 0.588, 0.804 and 1.241 at different periods, respectively). Furthermore, p27 protein expression was significantly inhibited by EGF (p27/beta-actin ratio was 0.225, 0.163, 0.107 and 0.082 after EGF treatment for 0, 24, 48 and 72 h, respectively). However, there was no detectable difference in p21 and p18 protein expression between EGF treatment and control groups (p21/beta-actin ratio was 0.432, 0.391, 0.407 and 0.329 and p18/beta-actin ratio was 0.268, 0.274, 0.231 and 0.309, respectively). CONCLUSIONS: This study suggests that EGF could induce RCE cell proliferation. EGF up-regulates cyclinD1 and CDK4 and down-regulates p27 in RCE cells. These changes may be the causes for EGF-induced proliferation of RCE.