The C-terminal of NSD2 regulates transcription of cell adhesion genes in multiple myeloma

The overexpression of the histone methyltransferase NSD2 (MMSET) in multiple myeloma (MM) patients plays a significant role in the development of this specific subtype of disease. Through the expansion of gene activation associated H3K36me2 and suppression of repressive H3K27me3 marks, NSD2 activates an aberrant set of genes that contribute to myeloma growth adhesive and invasive activities. NSD2 transcriptional activity also depends on its non-catalytic domains, which facilitate its recruitment to chromatin through histone binding. In this study, using NMR and ITC techniques, we demonstrate that the tandem PHD domain of NSD2 (PHDvC5HCHNSD2) acts as a reader for both unmodified histone H3K4 and three-methylated H3K27, making it the first PHD tandem cassette known to decode the methylation status of H3K27. We present a three-dimensional model of the complex based on NMR data and molecular dynamics simulations. Importantly, expression of mutants of PHDvC5HCHNSD2, designed to impair binding to the histone H3 tail in NSD2 deficient cells, leads to decreased activation of adhesive properties and cell adhesion genes and a decrease in corresponding H3K27ac signal at promoters. Moreover, expression of PHDvC5HCH mutant forms of NSD2 result in incomplete loss of H3K27 methylation throughout the genome compared to expression of wild-type NSD2. Collectively, these data indicate that PHDvC5HCH of NSD2 plays an important role in modulating gene expression and chromatin modification, thus opening new opportunities for pharmacological intervention.