Grant: Discovery Grants Program - Individual

Histone proteins and their many post-translational modifications (PTMs) are exquisitely conserved in eukaryotes where they regulate gene expression in diverse ways. Accordingly, the factors that control the deposition, removal, and interpretation of histone modifications are themselves deeply conserved, with many established to strongly impact normal biological processes in humans. A key type of PTM occurring on histones is lysine methylation. Lysine residues can be mono-, di-, or tri-methylated (Kme1, 2, 3) and these modification states have distinctive consequences reflecting the binding of Kme-specific binding proteins. Of central importance to the research proposed here, although numerous enzymes have been highly characterized with respect to their ability to dynamically control lysine methylation at specific histone residues, the known targets of these enzymes remain almost exclusively restricted to their respective histone substrates. My research program details the investigation of new targets of histone demethylase enzymes that we have already identified, as well as works toward the systematic discovery of yet unknown substrates of lysine demethylases. Jumonji C (JmjC) lysine demethylases (KDMs) catalyze the removal of methyl (-CH3) groups from modified lysyl residues and a prominent role for histone H3-K4me3 demethylation has been attributed to the KDM5 family; a family of JmjC-class KDMs. Indeed, the KDM5-family has been identified as `cancer drivers', belaying a critical need to better understand its fundamental biology beyond solely H3-K4me3 demethylation. The exceptions to this tenet have come from my lab's recent identification of histone H2B-K43me2 as a new substrate of KDM5B demethylation. However, the broader biological role(s) of these enzymes are increasingly being shown to also be attributed to non-histone demethylation. Furthering these ideas, my lab now has evidence to support that the KDM5 is capable of demethylating substrates that deviate from the H3-K4 sequence. From these studies, our most notable finding is that KDM5A demethylates the non-histone protein, p53 at K370me3. This represents the first non-histone substrate for this crucial protein family. Our findings to date identify new substrates of histone demethylase enzymes and suggest there are many more to be discovered. The specific objectives of this research program are (1) uncovering the functional implication of KDM5A/B demethylation of our newly discovered p53-K370me3 substrate, (2) build upon our study of the p53-K370me3 modification to uncover its biological implication, and (3) continue our study of KDM5 substrate selection and systematically expand the KDM5 enzyme-substrate network beyond histone H3-K4me2/3, H2B-K43me2 and p53-K370me3 substrates. The long-term objectives of my research program are to build upon both our new methodologies and our previous discoveries toward a new comprehension of the roles of lysine demethylation in the human cell.