Epigenetics and the associated post-translational modifications of histones are involved in multi-level gene regulation. Changes in the function of the enzymes that regulate histone modification can lead to changes in gene expression, which in turn can affect many cellular processes. Among these enzymes are the histone methyltransferases (HMTs) which methylate lysine and arginine amino acid residues on the histones. NSD (Nuclear Receptor SET Domain) The family is a subdivision of HMTs, consisting of 3 members NSD1, NSD2 and NSD3 in mammals and humans. NSD proteins are implicated in a variety of human diseases including many cancers. However, the molecular mechanisms through which deregulation of NSD proteins contribute to disease is unclear and there is no consensus about their catalytic specificity to histones. We will use advanced mass spectrometry to identify the specific biochemical activity of the NSD proteins. Interaction partners for the NSD proteins will be identified by purifying protein complexes followed by mass spectrometry. The NSD proteins are further characterized by their ability to bind to DNA and thereby affect gene regulation. We will therefore also investigate where on the genome NSD proteins specifically bind to clarify their effect on gene expression. It is expected that the proposed work will increase the understanding of how the NSD proteins help to develop cancer.