The incorporation loci of H3.3K36M determine its preferential prevalence in chondroblastomas.

The histone H3.3K36M mutation, identified in over 90% of chondroblastoma cases, reprograms the H3K36 methylation landscape and gene expression to promote tumorigenesis. However, it's still unclear how the H3K36M mutation preferentially occurs in the histone H3 variant H3.3 in chondroblastomas. Here, we report that H3.3K36M-, but not H3.1K36M-, mutant cells showed increased colony formation ability and differentiation defects. H3K36 methylations and enhancers were reprogrammed to different status in H3.3K36M- and H3.1K36M-mutant cells. The reprogramming of H3K36 methylation and enhancers was depended on the specific loci at which H3.3K36M and H3.1K36M were incorporated. Moreover, targeting H3K36M-mutant proteins to the chromatin inhibited the H3K36 methylation locally. Taken together, these results highlight the roles of the chromatic localization of H3.3K36M-mutant protein in the reprogramming of the epigenome and the subsequent induction of tumorigenesis, and shed light on the molecular mechanisms by which the H3K36M mutation mainly occurs in histone H3.3 in chondroblastomas.