SUMMARY Upon androgen stimulation, PKN1-mediated histone H3 threonine 11 phosphorylation (H3T11P) promotes AR target genes activation. However, the underlying mechanism is not completely understood. Here, we show that WDR5, a subunit of the SET1/MLL complex, interacts with H3T11P and this interaction facilitates the recruitment of the MLL1 complex and subsequent H3K4 trimethylation (H3K4me3). Using ChIP-seq, we find that androgen stimulation results in a six-fold increase in the number of H3T11P-marked regions and induces WDR5 colocalization to one third of H3T11P-enriched promoters, thus establishing a genome-wide relationship between H3T11P and recruitment of WDR5. Accordingly, PKN1 knock-down or chemical inhibition severely blocks WDR5 association and H3K4me3 on AR target genes. Finally, WDR5 is critical in prostate cancer cell proliferation, and is hyperexpressed in human prostate cancers. Together, these results identify WDR5 as a critical epigenomic integrator of histone phosphorylation and methylation and a major driver of androgen-dependent prostate cancer cell proliferation.

Androgen receptor (AR) plays pivotal roles in prostate cancer. Upon androgen stimulation, AR recruits the Protein kinase N1 (PKN1), which phosphorylates histone H3 at threonine 11, with subsequent recruitment of tryptophan, aspartic acid (WD) repeat-containing protein 5 (WDR5) and the su(var)3-9, enhancer of zeste, trithorax/mixed-lineage leukemia (SET1/MLL) histone methyltransferase complex to promote AR target gene activation and prostate cancer cell growth. However, the underlying mechanisms of target gene activation and cell growth subsequent to WDR5 recruitment are not well understood. Here, we demonstrate an epigenetic cross talk between histone modifications and AR target gene regulation. We discovered that K(lysine) acetyltransferase 8 (KAT8), a member of the MOZ, YBF2/SAS2, and TIP 60 protein 1 (MYST) family of histone acetyltransferases that catalyzes histone H4 lysine 16 acetylation, colocalized with WDR5 at AR target genes, resulting in hormone-dependent gene activation in prostate cancer cells. PKN1 or WDR5 knockdown severely inhibited KAT8 association with AR target genes and histone H4 lysine 16 acetylation upon androgen treatment. Knockdown of KAT8 significantly decreased AR target gene expression and prostate cancer cell proliferation. Collectively, these data describe a trans-histone modification pathway involving PKN1/histone H3 threonine 11 phosphorylation followed by WDR5/MLL histone methyltransferase and KAT8/histone acetyltransferase recruitment to effect androgen-dependent gene activation and prostate cancer cell proliferation.