Enzymes that modify histone tails play critical roles in transcription, cell proliferation, differentiation, aging and tumorigenesis. A main interest of my lab is to understand the molecular mechanism and biology of the CtBP (C-terminal binding protein) super- complex, which contains histone deacetylases (HDACs), methylases (G9a/EuHMT1), a demethylase (LSD1), and a nuclear protein (CDYL) that shares sequence homology with lipid metabolizing enzymes. In the past funding period, we discovered the first histone demethylase LSD1 and made breakthroughs in understanding the biological roles of CtBP and CDYL. Loss of Ce-CtBP function results in C. elegans life span extension, dependent on the forkhead transcription factor DAF-16/FOXO, which is the point of convergence of multiple signaling pathways that regulate life span. Microarray analysis identified ~200 putative Ce-CtBP target genes with functions in metabolism, stress response, transcription and translation. Our model is that Ce-CtBP regulates life span by intersecting with these signaling pathways and by antagonizing DAF-16. In this application, I will investigate the underlying molecular mechanisms by exploring the genetic and biochemical relationship between Ce-CtBP and the signaling pathways that regulate life span. Since DAF-16 interacts with Ce-CtBP in vitro, I will investigate whether this interaction is mediated by the putative CtBP-binding motif PIDLE located within DAF-16, and determine if physical interaction is important for Ce-CtBP to antagonize DAF16-mediated transcription and life span regulation. I will identify common target genes regulated by Ce-CtBP and DAF-16 by ChIP and ChIP-chip and investigate their roles in life span by RNAi and over-expression experiments. The proposed studies will identify players and pathways involved in Ce-CtBP-mediated life span regulation. Purification of CDYL-interacting proteins led us to the exciting discovery that CDYL bridges the interaction of the neuronal gene master regulator, REST, and the histone methylase G9a to repress gene transcription. REST is also a newly identified tumor suppressor. We found that CDYL and G9a, but not CoREST (another REST co- repressor) may mediate REST tumor suppression, identifying CDYL and G9a as novel candidate tumor suppressors. We will investigate CDYL tumor suppression in clinical cancers and explore the molecular mechanisms by which CDYL regulates tumor suppression. Given its homology to lipid metabolizing enzymes and ability to bind CoA, we will also explore whether binding of CoA and its lipid derivatives regulate CDYL transcription and tumor suppression functions. Our proposed investigations of CtBP and CDYL offer a unique opportunity to gain novel insights into chromatin regulation in critical biological processes such as ageing and cancer, and have the potential to uncover a new facet of metabolic regulation of chromatin-based processes.
This application proposes to study two proteins that regulate life span, metabolism and tumorigenensis, respectively. Findings will provide new insights into mechanisms that control these processes and may help future development of small molecules that modulate metabolism, aging and oncogenesis.
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