PHF8 functions as a transcriptional coactivator that regulates HER2 expression. a.Chromatin immunoprecipitation (ChIP) analysis of PHF8 bound to HER2 in HER2+ cells. Enrichment of PHF8 on the HER2 promoter 1 (P1), promoter 2 (P2), HER2 gene body regulatory element (HGE), and an unmodified region (NC) were analysed using ChIP-qPCR. Relative enrichment represents the average fold-enrichment of PHF8 vs. the input, normalised to the NC region. b. Western blotting and RT-PCR analyses of the levels of HER2 and its mRNA in the indicated cells with and without PHF8 knockdown. NC: control scrambled siRNA or shRNA; PHF8-siRNAs, PHF8-si1 and PHF8-si2 and PHF8 shRNAs, PHF8-sh1 and PHF8-sh2, are described in the methods section. Lower panel: RT-qPCR analysis of HER2 mRNA expression normalised to that of RPL13A. c. ChIP-qPCR analysis of the recruitment of H3K27ac, H3K4me3, and TFAP2C to HER2 in HER2+ cells with PHF8 knockdown. The Student t-test was performed to evaluate the significance of differences between variables. * p ≤ 0.05, ** p ≤ 0.01.