Hijacking a key chromatin modulator creates epigenetic vulnerability for MYC-driven cancer.

While the genomic binding of MYC protein correlates with active epigenetic marks on chromatin, it remains largely unclear how major epigenetic mechanisms functionally impact the tumorigenic potential of MYC. Here, we show that, compared with the catalytic subunits, the core subunits, including DPY30, of the major H3K4 methyltransferase complexes were frequently amplified in human cancers and selectively upregulated in Burkitt lymphoma. We show that DPY30 promoted the expression of endogenous MYC and was also functionally important for efficient binding of MYC to its genomic targets by regulating chromatin accessibility. Dpy30 heterozygosity did not affect normal animal physiology including lifespan, but significantly suppressed Myc-driven lymphomagenesis, as cells failed to combat oncogene-triggered apoptosis as a result of insufficient epigenetic modulation and expression of a subset of antiapoptotic genes. Dpy30 reduction also greatly impeded MYC-dependent cellular transformation, without affecting normal cell growth. These results suggest that MYC hijacks a major epigenetic pathway - H3K4 methylation - to facilitate its molecular activity in target binding and to coordinate its oncogenic program for efficient tumorigenesis, meanwhile creating "epigenetic vulnerability." DPY30 and the H3K4 methylation pathway are thus potential epigenetic targets for treating certain MYC-driven cancers.