Homeostatic Regulation of Folate Metabolism

描述（由申请人提供）：我们建议阐明在DNA合成位点调节de novo thymidylate （dTMP）合成的生化、遗传和营养因素，并建立这一途径中潜在的损伤机制。叶酸和维生素b12依赖性单碳（1C）代谢受损与许多常见病理有关，但机制尚未确定。最近，我们报道了Shmt-/+小鼠模型在DNA中积累尿嘧啶，并对肠道肿瘤和神经管缺陷敏感。SHMT1是唯一报道的叶酸依赖酶，其破坏导致叶酸反应性神经管缺陷。我们的研究结果表明，核和线粒体dTMP生物合成是叶酸和维生素b12相关疾病的基础。通过这些研究，我们将建立对细胞核和线粒体中1C通路的基本理解，阐明特定维生素和代谢物对其的调节，并表征其在维持基因组完整性方面的作用。这些研究还将确定dTMP生物合成与DNA表观遗传修饰之间是否存在代谢相互作用。这些结果将为未来的人体研究提供信息，这些研究将转化为预防和治疗叶酸和维生素b12相关疾病的医疗实践和公共卫生政策。目的1：确定MTHFD1和KDM1酶对细胞核中维生素B12和叶酸介导的1C代谢的贡献。这些研究将确定和描述两种叶酸利用酶MTHFD1和KDM1的作用，它们是合成dTMP的核多酶复合物的组成部分，并与DNA复制机制相关。这些研究还将确定核dTMP生物合成和表观遗传染色质修饰是否通过叶酸辅助因子的使用而相互依赖。目的二世。阐明核dTMP合成调控的决定因素和机制。这些研究将确定核叶酸依赖酶在dTMP合成中的作用、调控和贡献。研究包括对核dTMP生物合成和基因组稳定性的营养、代谢和遗传因素的调查。第三目标。阐明线粒体dTMP合成调控的决定因素和机制。这些研究将确定线粒体叶酸依赖酶在dTMP合成中的作用、调控和贡献，包括控制线粒体dTMP生物合成和线粒体基因组稳定性的营养、代谢和遗传因素。

DESCRIPTION (provided by applicant): We propose to elucidate the biochemical, genetic and nutritional factors that regulate de novo thymidylate (dTMP) synthesis at the sites of DNA synthesis, and establish the mechanisms underlying impairments in this pathway. Impaired folate- and vitamin B12-dependent one-carbon (1C) metabolism is associated with numerous common pathologies, but mechanisms have yet to be established. Recently, we reported that the Shmt-/+ mouse model accumulates uracil in DNA and is sensitized to intestinal tumors and neural tube defects. SHMT1 is the only reported folate-dependent enzyme whose disruption results in folate-responsive neural tube defects. Our findings indicate that nuclear and mitochondrial dTMP biosynthesis underlies folate- and vitamin B12-related disease. As a result of these studies, our fundamental understanding of 1C pathways in the nucleus and mitochondria will be established, their regulation by specific vitamins and metabolites elucidated, and their role in maintaining genome integrity characterized. These studies will also determine if there are metabolic interactions between nuclear de novo dTMP biosynthesis and epigenetic modifications to DNA. The results will inform future human studies that translate into medical practice and public health policy for the prevention and treatment of folate- and vitamin B12-associated pathologies. The three related and overlapping areas to be investigated are: Aim I. Determine the contributions of the enzymes MTHFD1 and KDM1 to vitamin B12- and folate-mediated 1C metabolism in the nucleus. These studies will identify and characterize the role of two folate-utilizing enzymes, MTHFD1 and KDM1, as components of a nuclear multienzyme complex that synthesizes dTMP and associates with the DNA replication machinery. These studies will also determine if nuclear dTMP biosynthesis and epigenetic chromatin modifications are interdependent through their use of folate cofactors. Aim II. Elucidate the determinants and mechanisms of nuclear dTMP synthesis regulation. These studies will determine the role, regulation and contribution of nuclear folate-dependent enzymes in dTMP synthesis. Studies include investigations into the nutritional, metabolic and genetic factors that govern nuclear dTMP biosynthesis and genome stability. AIM III. Elucidate the determinants and mechanisms of mitochondrial dTMP synthesis regulation. These studies will determine the role, regulation and contribution of mitochondrial folate-dependent enzymes in dTMP synthesis, including the nutritional, metabolic and genetic factors that govern mitochondrial dTMP biosynthesis and mitochondrial genome stability. PUBLIC HEALTH RELEVANCE: Folate- and vitamin B12-associated pathologies are common but their underlying mechanisms and pathways are not understood, and folic acid supplementation alone is not sufficient to reduce or eliminate risk of these pathologies and may do harm. The experiments proposed in this application build on recent findings from our laboratory that several folate- and vitamin B12- related pathologies result from impaired thymidylate biosynthesis. The results from these experiments will inform future human studies and ultimately translate into medical practice and public health policy for the prevention and treatment of folate- and vitamin B12-associated pathologies.