The function of PHF19 (PHD finger protein 19, Ensembl gene identifier ENSG00000119403) is as follows. Polycomb group (PcG) protein that specifically binds histone H3 trimethylated at 'Lys-36' (H3K36me3) and recruits the PRC2 complex, thus enhancing PRC2 H3K27me3 methylation activity (PubMed:15563832, PubMed:18691976, PubMed:23104054, PubMed:23160351, PubMed:23228662, PubMed:23273982, PubMed:29499137, PubMed:31959557). Probably involved in the transition from an active state to a repressed state in embryonic stem cells: acts by binding to H3K36me3, a mark for transcriptional activation, and recruiting H3K36me3 histone demethylases RIOX1 or KDM2B, leading to demethylation of H3K36 and recruitment of the PRC2 complex that mediates H3K27me3 methylation, followed by de novo silencing (PubMed:23160351). Recruits the PRC2 complex to CpG islands and contributes to embryonic stem cell self- renewal. Also binds histone H3 dimethylated at 'Lys-36' (H3K36me2) (PubMed:23104054). Isoform 1 and isoform 2 inhibit transcription from an HSV-tk promoter (PubMed:15563832). {ECO:0000269|PubMed:15563832, ECO:0000269|PubMed:18691976, ECO:0000269|PubMed:23104054, ECO:0000269|PubMed:23160351, ECO:0000269|PubMed:23228662, ECO:0000269|PubMed:23273982, ECO:0000269|PubMed:29499137, ECO:0000269|PubMed:31959557}.