In this study we leveraged a comprehensive panel of mMSC lines harboring combinatorial deletions of all five K36MTs—NSD1, NSD2, NSD3, ASH1L, and SETD2—alongside complementary analyses in human HNSCC lines expressing the H3K36M oncohistone, to dissect the downstream consequences of H3K36me loss at multiple levels of chromatin function. Here, ASH1L is linked to head and neck squamous cell carcinoma.