KMT5A and breast cancer: For another, co‐transfection of wild type (WT) SETD8 but not the inactive R336G mutant with MYC significantly reduced the ubiquitination level and prolonged the half‐life of MYC (Figure S2k,l, Supporting Information).[9] All these results indicated that SETD8 stabilizes MYC protein by inhibiting its ubiquitin‐proteasome degradation in BC.