MTHFD1 links folate metabolism to BRD4-mediated transcriptional regulation
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ABSTRACT: The histone acetyl-reader BRD4 is an important regulator of chromatin structure and transcription, yet factors modulating its activity have remained elusive. Here we describe two complementary screens for functional regulators and physical interactors of BRD4, which converge on the folate pathway enzyme MTHFD1. We show that a fraction of MTHFD1 resides in the nucleus, where it is recruited to distinct genomic loci by direct interaction with BRD4. Inhibition of either BRD4 or MTHFD1 results in similar changes in nuclear metabolite composition and gene expression, and pharmacologic inhibitors of the two pathways synergize to impair cancer cell viability in vitro and in vivo. Our finding that MTHFD1 and other metabolic enzymes are chromatin-associated suggests a direct role for nuclear metabolism in the control of gene expression.
Project description:The histone acetyl-reader BRD4 is an important regulator of chromatin structure and transcription, yet factors modulating its activity have remained elusive. Here we describe two complementary screens for genetic and physical interactors of BRD4, which converge on the folate pathway enzyme MTHFD1. We show that a fraction of MTHFD1 resides in the nucleus, where it is recruited to distinct genomic loci by direct interaction with BRD4. Inhibition of either BRD4 or MTHFD1 results in similar changes in nuclear metabolite composition and gene expression, and pharmacologic inhibitors of the two pathways synergize to impair cancer cell viability in vitro and in vivo. Our finding that MTHFD1 and other metabolic enzymes are chromatin-associated suggests a direct role for nuclear metabolism in the control of gene expression.
Project description:The histone acetyl-reader BRD4 is an important regulator of chromatin structure and transcription, yet factors modulating its activity have remained elusive. Here we describe two complementary screens for genetic and physical interactors of BRD4, which converge on the folate pathway enzyme MTHFD1. We show that a fraction of MTHFD1 resides in the nucleus, where it is recruited to distinct genomic loci by direct interaction with BRD4. Inhibition of either BRD4 or MTHFD1 results in similar changes in nuclear metabolite composition and gene expression, and pharmacologic inhibitors of the two pathways synergize to impair cancer cell viability in vitro and in vivo. Our finding that MTHFD1 and other metabolic enzymes are chromatin-associated suggests a direct role for nuclear metabolism in the control of gene expression. BRD4 is an important chromatin regulator with roles in gene regulation, DNA damage, cell proliferation and cancer progression1-4. The protein is recruited to distinct genomic loci by the interaction of its tandem bromodomains with acetylated lysines on histones and other nuclear proteins5. There, BRD4 acts as a transcriptional activator by P-TEFb-mediated stimulation of transcriptional elongation6. The activating function of BRD4 on key driver oncogenes like MYC have made this epigenetic enzyme an important therapeutic target in both BRD4 translocated and BRD4 wild-type cancers3,7-12, and at least seven bromodomain inhibitors have reached the clinical stage13. Genome-wide studies have identified the role of BRD4-induced epigenetic heterogeneity in cancer cell resistance14, and factors defining BRD4 inhibitor response15,16. However, despite its clinical importance and the broad role of BRD4 in chromatin organization, surprisingly little is known about factors that are directly required for BRD4 function. To systematically expand the list of known BRD4 interactors5 and to characterize proteins directly required for BRD4 function, we developed a strategy of two complementary screens for genetic and physical partners of BRD4. The two approaches converge on a single factor, methylenetetrahydrofolate dehydrogenase 1 (MTHFD1). Our description of a transcriptional role for this C-1-tetrahydrofolate synthase highlights a direct connection between nuclear folate metabolism and cancer regulation.
Project description:The metabolic pathways that underlie the association between folate deficiency and increased risk for colorectal cancer (CRC) remain unclear. We have studied the effect of C1THF synthase (encoded by the Mthfd1 gene) and dietary folate and choline on intestinal tumor development in Apcmin/+ mice and azoxymethane (AOM)-induced colon cancer in mice. Mthfd1 deficiency did not alter tumor number or load in Apcmin/+ mice, but did result in a decreased incidence of colon tumors. Conversely, Mthfd1 deficiency increased tumor number 3.5-fold and tumor load 2-fold in AOM-treated mice. Here we tested colons isolated from wildtype and Mthfd1-deficient animals for alterations in gene expression. Keywords: genetic modification RNA was isolated from proximal colons of MTHFD heterozygous and wild-type mice raised on a control diet. Three colon samples were isolated from each genotype to provide biological replication.
Project description:The metabolic pathways that underlie the association between folate deficiency and increased risk for colorectal cancer (CRC) remain unclear. We have studied the effect of C1THF synthase (encoded by the Mthfd1 gene) and dietary folate and choline on intestinal tumor development in Apcmin/+ mice and azoxymethane (AOM)-induced colon cancer in mice. Mthfd1 deficiency did not alter tumor number or load in Apcmin/+ mice, but did result in a decreased incidence of colon tumors. Conversely, Mthfd1 deficiency increased tumor number 3.5-fold and tumor load 2-fold in AOM-treated mice. Here we tested colons isolated from wildtype and Mthfd1-deficient animals for alterations in gene expression. Keywords: genetic modification
Project description:Folate metabolism provides the building blocks of many classes of biomolecules including purine nucleotides, thymidylate, serine and methionine and is an important target of antimetabolite drugs. A central enzyme in the pathway is the trifunctional MTHFD1, that catalyzes the interconversion of folates by its formyltetrahydrofolate synthetase and methylenetetrahydrofolate dehydrogenase/methenyltetrahydrofolate cyclohydrolase domains. Here, we employ large-scale chemical and genome-wide genetic screens to investigate the chemical and genetic dependencies caused by MTHFD1 loss-of-function and uncover a central role of the enzyme in balancing the response to extracellular adenosine. We show that adenosine is essential in MTHFD1KO cells, where adenine-containing compounds counter AMPK activation and increase proliferation in a PARP8, ATF7 and PML-dependent manner. In contrast, adenosine supplementation causes strong toxicity in patient-derived MTHFD1-derived cells harboring dehydrogenase/cyclohydrolase domain mutations. This response, mediated by replication stress and activation of the DNA damage response, is dependent on the nucleotide salvage enzyme HRPT1 and on NUDT5, an enzyme involved in nuclear ATP generation. Our findings suggest an evolutionary rationale for integrating three distinct enzymatic activities within the single MTHFD1 protein and propose the application of dehydrogenase/cyclohydrolase inhibitors in tumors located in an adenosine-rich microenvironment.
Project description:In order to further investigate silencing mechanisms, we screened a mutagenized Arabidopsis thaliana population for expression of SDCpro-GFP, redundantly controlled by DNA methyltransferases DRM2 and CMT3. We identified the hypomorphic mutant mthfd1-1, carrying a mutation (R175Q) in the cytoplasmic bifunctional methylenetetrahydrofolate dehydrogenase/methenyltetrahydrofolate cyclohydrolase (MTHFD1). Accumulation of homocysteine and S-adenosylhomocysteine, genome-wide DNA hypomethylation, loss of H3K9me, and transposon derepression indicate that S-adenosylmethionine-dependent transmethylation is inhibited in mthfd1-1.
Project description:[Abstract] The R653Q variant in the synthetase domain of the folate-metabolizing enzyme MTHFD1 has been shown to increase risk for birth defects, but it does not affect risk for development of colorectal cancer (CRC). However, since we have shown that this variant reduces purine synthesis, the goal of this study was to determine whether it could affect tumor growth. Using our mouse model for MTHFD1-synthetase deficiency (Mthfd1S+/-), we induced tumor formation with azoxymethane (AOM) and dextran sodium sulfate (DSS) in male and female wild-type and Mthfd1S+/- mice. Tumor size was significantly smaller due to mutant genotype, particularly in males. Tumor size was increased in female mice compared with males, regardless of genotype. Tumor number was not influenced by genotype and was lower in females. Inflammation within tumors of male Mthfd1S+/- mice was lower than in wild-type mice. Proliferation of mouse embryonic fibroblasts from mutant lines was slower than that in wild-type fibroblasts. Gene expression analysis in tumor adjacent normal (preneoplastic) tissue identified several genes involved in proliferation (Fosb, Fos, Ptk6, Esr2, Atf3) or inflammation (Atf3, Saa1, TNF-α) that were downregulated in mutant male mice. Female mutants did not have changes in expression for those genes, nor in tumor inflammation levels, compared with wild-type, suggesting a different mechanism directing tumor growth in females. We suggest that restriction of purine synthesis and reduced expression of critical tumor-promoting genes leads to slower tumor growth in MTHFD1-synthetase deficiency. These findings may have implications for CRC tumor growth and prognosis in individuals with the R653Q variant.
Project description:What is known is that methionine-dependency is a feature of some cancers. So far, it was attributed to mutations in genes involved in the methionine de novo or salvage pathways. What is new is that in this work we propose that methionine dependency stems from an altered cellular metabolism. We provide evidence that in U251 glioblastoma cell line, only cancer stem cells -isolated as tumor spheres in non adherent conditions- are methionine dependent and not monolayer cells grown in adherent conditions. Transcriptome wide-sequencing reveals that several genes involved in cytosolic folate cycle are downregulated whereas some transcripts of genes involved in mitochondrial folate cycle are upregulated. Genome wide DNA methylation does not account for these changes in gene expression. Mass spectrometry measurements confirm that tumor spheres display low cytosolic folate cycle unable to produce enough 5-methyltetrahydrofolate to remethylate homocystein to methionine. This decreased 5-methyltetrahydrofolate bioavailability is presumably due to a reprogrammed mitochondrial folate cycle which instead of synthesizing formate, intended to fuel the cytosolic folate cycle, oxidizes the formyl group to CO2 with the attendant reduction of NADP+ to NADPH and release of tetrahydrofolate. The originality of this work resides in that it replaces methionine deprivation as a useful nutritional strategy in cancer growth control since cancer stem cells are much more tumoregenic than their non stem-like counterparts. Second, it reveals that the primary default responsible of the reprogrammation of folate metabolism originates in the mitochondria. Thus, mitochondrial enzymes could be novel and more promising anticancer targets than dihydrofolate reductase (DHFR), the current target of drug therapy linked with folate metabolism.
Project description:Folate is a vitamin essential for cell growth and has been used to prevent congenital abnormalities. However, little is known about how folate affects health in older adults. We examined healthspan as a function of dietary folate intake. To begin to measure such effects, we performed a small (2x2; sex-by-diet) pilot study in the long-lived inbred mouse strain C57BL/6.