title: Nuclear enrichment of folate cofactors and methylenetetrahydrofolate dehydrogenase 1 (MTHFD1) protect de novo thymidylate biosynthesis during folate deficiency.
abstract: Folate-mediated one-carbon metabolism is a metabolic network of interconnected pathways that is required for the de novo synthesis of three of the four DNA bases and the remethylation of homocysteine to methionine. Previous studies have indicated that the thymidylate synthesis and homocysteine remethylation pathways compete for a limiting pool of methylenetetrahydrofolate cofactors and that thymidylate biosynthesis is preserved in folate deficiency at the expense of homocysteine remethylation, but the mechanisms are unknown. Recently, it was shown that thymidylate synthesis occurs in the nucleus, whereas homocysteine remethylation occurs in the cytosol. In this study we demonstrate that methylenetetrahydrofolate dehydrogenase 1 (MTHFD1), an enzyme that generates methylenetetrahydrofolate from formate, ATP, and NADPH, functions in the nucleus to support de novo thymidylate biosynthesis. MTHFD1 translocates to the nucleus in S-phase MCF-7 and HeLa cells. During folate deficiency mouse liver MTHFD1 levels are enriched in the nucleus >2-fold at the expense of levels in the cytosol. Furthermore, nuclear folate levels are resistant to folate depletion when total cellular folate levels are reduced by >50% in mouse liver. The enrichment of folate cofactors and MTHFD1 protein in the nucleus during folate deficiency in mouse liver and human cell lines accounts for previous metabolic studies that indicated 5,10-methylenetetrahydrofolate is preferentially directed toward de novo thymidylate biosynthesis at the expense of homocysteine remethylation during folate deficiency.
authors.affiliation: From the Division of Nutritional Sciences, Cornell University, Ithaca, New York 14853 and.
authors.forename: Martha S
authors.initials: MS
authors.lastname: Field
authors.affiliation: From the Division of Nutritional Sciences, Cornell University, Ithaca, New York 14853 and.
authors.forename: Elena
authors.initials: E
authors.lastname: Kamynina
authors.affiliation: From the Division of Nutritional Sciences, Cornell University, Ithaca, New York 14853 and.
authors.forename: Olufunmilayo C
authors.initials: OC
authors.lastname: Agunloye
authors.affiliation: From the Division of Nutritional Sciences, Cornell University, Ithaca, New York 14853 and.
authors.forename: Rebecca P
authors.initials: RP
authors.lastname: Liebenthal
authors.affiliation: Department of Biochemistry, Memorial University of Newfoundland, St. John's, Newfoundland A1B 3X9, Canada.
authors.forename: Simon G
authors.initials: SG
authors.lastname: Lamarre
authors.affiliation: Department of Biochemistry, Memorial University of Newfoundland, St. John's, Newfoundland A1B 3X9, Canada.
authors.forename: Margaret E
authors.initials: ME
authors.lastname: Brosnan
authors.affiliation: Department of Biochemistry, Memorial University of Newfoundland, St. John's, Newfoundland A1B 3X9, Canada.
authors.forename: John T
authors.initials: JT
authors.lastname: Brosnan
authors.affiliation: From the Division of Nutritional Sciences, Cornell University, Ithaca, New York 14853 and pjs13@cornell.edu.
authors.forename: Patrick J
authors.initials: PJ
authors.lastname: Stover
mesh_terms: D000818:Animals; D059447:Cell Cycle Checkpoints; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism*; D003067:Coenzymes / Q000378:metabolism*; D004247:DNA / Q000378:metabolism; D004032:Diet; D005260:Female; D005492:Folic Acid / Q000378:metabolism*; D005494:Folic Acid Deficiency / Q000201:enzymology* / Q000473:pathology; D005561:Formates / Q000097:blood; D055785:Gene Knockdown Techniques; D012696:Glycine Hydroxymethyltransferase / Q000378:metabolism; D006801:Humans; D008099:Liver / Q000201:enzymology; D008297:Male; D008715:Methionine / Q000096:biosynthesis; D008754:Methylenetetrahydrofolate Dehydrogenase (NADP) / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D021381:Protein Transport; D011687:Purines / Q000096:biosynthesis; D016196:S Phase; D013938:Thymidine Monophosphate / Q000096:biosynthesis*; D014498:Uracil / Q000378:metabolism
chemical_list: D003067:Coenzymes; D005561:Formates; D011687:Purines; D013938:Thymidine Monophosphate; D014498:Uracil; D004247:DNA; D005492:Folic Acid; D008715:Methionine; D008754:Methylenetetrahydrofolate Dehydrogenase (NADP); D012696:Glycine Hydroxymethyltransferase; C559685:Shmt1 protein, mouse
keywords: Cell Compartmentalization; DNA Synthesis; Folate; Homocysteine; MTHFD1; Nucleoside/Nucleotide Metabolism; One-carbon Metabolism; Uracil