Study of NSD2 using a dTAG system reveals their molecular mechanism and oncogenic implications in t(4;14) multiple myeloma

The H3K36me2 methyltransferase NSD2 is deleted in Wolf-Hirschhorn syndrome and aberrantly expressed in 10-15% of multiple myeloma (MM) due to a t(4;14) translocation. Although NSD2 is thought to be a primary driver in MM, the exact molecular mechanisms by which it regulates transcription remain unclear. We applied the dTAG system to acutely degrade NSD2 and used this, in combination with time-resolved SLAM-seq, to identify 307 transcriptional targets of NSD2. Reconstitution with either wild-type NSD2 or a catalytically inactive mutant (NSD2Y1179A) showed that NSD2's transcriptional effects are almost exclusively dependent on its SET domain activity. Mechanistically, H3K36me2 deposition by NSD2 antagonizes H3K27me3 levels, and treatment with two distinct PRC2 inhibitors demonstrated that approximately half of NSD2 target genes are regulated in an H3K27me3-dependent manner. CUT&Tag analysis showed that upon NSD2 depletion there was an increase in H3K27me3 that occurred at genome-wide intergenic regions, rather than at the promoters or gene bodies of NSD2 target genes. These data suggest that NSD2, via H3K36me2, antagonizes H3K27me3 deposition likely at distal regulatory elements including enhancers, creating a chromatin landscape favorable for target gene transcription. Importantly, NSD2 target genes were enriched for key oncogenic pathways, and 24 transcription factors implicated in neurodevelopment and acute leukemia, consistent with its role in Wolf-Hirschhorn syndrome and MM. Eight of these transcription factors are known oncogenic drivers in acute leukemia or MM, highlighting a novel molecular mechanism for NSD2's role in t(4;14) MM.