Abstract 1060: Structural insights into the regulation and the recognition of histone marks by the SET domain of histone lysine HMTase NSD1, NSD2/MMSET/WHSC1, and NSD3/WHSC1L1

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Abstract Background: The nuclear receptor binding SET domain (NSD) protein is a family of three histone-lysine N-methyltransferase (HMTase), NSD1, NSD2/MMSET/WHSC1, and NSD3/WHSC1L1 that are critical in maintaining the chromatin integrity. NSD1 methylates H3K36 and H4K20 and is associated with acute myeloid leukemia, multiple myeloma, and lung cancer. The NSD1-NUP98 translocation plays a significant role in childhood acute myeloid leukemia with NUP98-NSD1 being an active H3K36 methylase. NSD1 is amplified in multiple myeloma, lung cancer, neuroblastomas and glioblastomas. NSD2 methylates H3K36 and is linked to prostate cancer and multiple myeloma. Over expression of NSD2 in myeloma cells leads to aberrantly high levels of H3K36 di-methylation, accompanied by a decrease in H3K27 methylation. NSD2 is found over expressed in fifteen different cancers and is associated with tumor aggressiveness or prognosis in most types of cancers. NSD3 methylates H3K36 and is associated with both lung and breast cancers along with the acute myeloid leukemia. The amplification of either NSD1 or NSD2 triggers the cellular transformation. NSD3 is found amplified in breast cancer cell lines and primary breast carcinomas. Reducing NSDs activity through specific and selective lysine-HMTase inhibitors appears promising to help suppressing cancer growth. Little is known about the NSD pathways and our understanding of the histone Lysine-HMTase mechanism is partial. The SET domain of NSD1 has specific mechanisms to recognize histone marks unlike other HMTase. The precise catalytic activities of the NSDs are obscure and discrepancies exist hindering progress in understanding their exact biological functions and pathways in cancer pathogenesis. In this study, we explored the in vitro catalytic activities on histone substrates to understand the substrate recognition and to pave the way for the design of selective and specific NSD inhibitors usable in cancer therapies. Methods: We used both biochemical and computational methods to understand the substrates recognition by the NSDs and to investigate the structural mechanisms happening in the SET domain during the binding of histone tails. Results: A key regulatory and a recognition mechanism is driven by the flexibility of a loop at the interface of the SET and postSET region who rotates ∼45° and translated 7Å opening the SET domain for the binding of the peptide ligand. This regulatory loop acts as a seat belt for the ligand and contributes to the discrimination and the substrate specificity. In vitro, The SET domain of the NSDs favor H3 recognition and are able to methylate a range of substrate. To reconcile with the in vivo activities previously reported on H3K36 and H4K20, we propose a cross-talk mechanism controlling the substrate recognition. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1060. doi:1538-7445.AM2012-1060