Understanding the contribution of inositol phosphate signalling to class-1 HDAC complex function

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'Histone deacetylase' (HDAC) enzymes are present in all cells of the body. Their function is to switch genes 'off', and make sure they stay 'off'. In many respects shutting a gene down is every bit as important as switching a gene on. HDAC enzymes represent an exciting medical opportunity because they are 'druggable'. Already, drugs which inhibit HDAC activity are being used in the clinic as anti-cancer agents, and in the laboratory for their beneficial effects on dementia and anti-inflammatory properties. There is therefore a compelling applied, as well as academic, motivation for studying their physiological roles in order to assess their potential as pharmacological targets. We use a technique called 'X-ray crystallography' which allows us to determine the shape and structure of HDAC enzymes at a molecular level. Once we have determined their shape it allows us to understand the way that HDACs bind to other proteins and small molecules such as inositol phosphate (IP). We recently showed in vitro (i.e. in a test tube) that the enzymatic activity of HDACs was dependent upon the binding of IP. Following on from this discovery, the purpose of this project is to understand the importance of IP to HDAC function in cells and in mice. To do this we have three main objectives: 1) We plan to generate cells with low, medium and high levels of IP and test whether these correlate with level of HDAC activity. 2) In cells, HDACs interact with other proteins to form a multi-protein 'complex'. The complex most sensitive to the presence of IP is called, MIDAC and it consists of three proteins bound together (HDAC1, DNTTIP1 and MIDEAS). To understand the regulation of HDAC complexes by IP we plan to solve the structure of MIDAC using X-ray crystallography. 3) The role of MIDAC in cells is completely unknown and so we aim characterize the physiological activity of MIDAC, using cells lacking one of the three members of the complex, DNTTIP1. By understanding the molecular basis of HDAC complex function we can use that knowledge to design new drugs to prevent them from working. The ability to stop HDACs from working has beneficial effects on a wide-range of diseases, including epiplepsy, bipolar dissorder and Alzheimer's disease, making them excellent drug targets.