Arsenic trioxide targets MTHFD1 and SUMO-dependent nuclear de novo thymidylate biosynthesis

• Published in: Proceedings of the National Academy of Sciences - PNAS 2017-03, Vol.114 (12), p.E2319-E2326
• Main Authors: Kamynina, Elena, Lachenauer, Erica R., DiRisio, Aislyn C., Liebenthal, Rebecca P., Field, Martha S., Stover, Patrick J.
• Format: Article
• Language: English
• Subjects: Aminohydrolases - antagonists & inhibitors; Aminohydrolases - genetics; Aminohydrolases - metabolism; Animal models; Animals; Arsenic; Arsenic Trioxide; Arsenicals; Biological Sciences; Biosynthesis; Cell Line; Cell Nucleus - drug effects; Cell Nucleus - enzymology; Cell Nucleus - genetics; Cell Nucleus - metabolism; Deoxyribonucleic acid; DNA; Enzymes; Fibroblasts - drug effects; Fibroblasts - enzymology; Fibroblasts - metabolism; Formate-Tetrahydrofolate Ligase - antagonists & inhibitors; Formate-Tetrahydrofolate Ligase - genetics; Formate-Tetrahydrofolate Ligase - metabolism; Genomic Instability - drug effects; Glycine Hydroxymethyltransferase - genetics; Glycine Hydroxymethyltransferase - metabolism; Humans; Inorganic chemistry; Methylenetetrahydrofolate Dehydrogenase (NADP) - antagonists & inhibitors; Methylenetetrahydrofolate Dehydrogenase (NADP) - genetics; Methylenetetrahydrofolate Dehydrogenase (NADP) - metabolism; Mice; Mice, Knockout; Multienzyme Complexes - antagonists & inhibitors; Multienzyme Complexes - genetics; Multienzyme Complexes - metabolism; Oxides - toxicity; PNAS Plus; Proteolysis; Small Ubiquitin-Related Modifier Proteins - antagonists & inhibitors; Small Ubiquitin-Related Modifier Proteins - genetics; Small Ubiquitin-Related Modifier Proteins - metabolism; Sumoylation; Thymidine Monophosphate - biosynthesis; Thymidylate Synthase - genetics; Thymidylate Synthase - metabolism; Uracil - metabolism
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.1619745114

Arsenic exposure increases risk for cancers and is teratogenic in animal models. Here we demonstrate that small ubiquitin-like modifier (SUMO)- and folate-dependent nuclear de novo thymidylate (dTMP) biosynthesis is a sensitive target of arsenic trioxide (As₂O₃), leading to uracil misincorporation into DNA and genome instability. Methylenetetrahydrofolate dehydrogenase 1 (MTHFD1) and serine hydroxymethyltransferase (SHMT) generate 5,10-methylenetetrahydrofolate for de novo dTMP biosynthesis and translocate to the nucleus during S-phase, where they form a multienzyme complex with thymidylate synthase (TYMS) and dihydrofolate reductase (DHFR), as well as the components of the DNA replication machinery. As₂O₃ exposure increased MTHFD1 SUMOylation in cultured cells and in in vitro SUMOylation reactions, and increased MTHFD1 ubiquitination and MTHFD1 and SHMT1 degradation. As₂O₃ inhibited de novo dTMP biosynthesis in a dose-dependent manner, increased uracil levels in nuclear DNA, and increased genome instability. These results demonstrate that MTHFD1 and SHMT1, which are key enzymes providing one-carbon units for dTMP biosynthesis in the form of 5,10-methylenetetrahydrofolate, are direct targets of As₂O₃-induced proteolytic degradation, providing a mechanism for arsenic in the etiology of cancer and developmental anomalies.