Biology subjects

Heintzman, D. R.

Publications and source records attributed to Heintzman, D. R..

5 recordsLinked to original sources

bioRxiv2026

Topoisomerase IIIα resolves inter- and intra-molecular intertwines during DNA replication

Resolution of topological stress is crucial for genome integrity. Vertebrate topoisomerase II (TOP2) resolves catenanes to relieve topological stress and unlink daughter molecules during DNA replication. Topoisomerase III (TOP3) can also resolve catenanes, but its direct role during DNA replication, substrate specificity, and relevant binding partners remain unclear. Here we show that TOP3 becomes crucial when TOP2 function is compromised. We find that in Xenopus egg extracts, TOP3 promotes replication fork progression and daughter strand unlinking specifically during replication termination. TOP3 can carry out this role independently of its binding partners RMI1-RMI2 and the BLM helicase by acting on lagging-strand single-stranded DNA (ssDNA). Strikingly, elevated lagging-strand ssDNA drives formation of intramolecular ssDNA intertwines, which are ordinarily resolved by TOP3. Thus, TOP3 resolves intermolecular linkages to promote fork progression during termination and resolves intramolecular linkages that arise when high levels of ssDNA are present during DNA replication.

biochemistry↗

bioRxiv2025

Impaired oxidative phosphorylation drives primary tumor escape and metastasis

Metastasis causes most cancer deaths and reflects transitions from primary tumor escape to seeding and growth at metastatic sites. Epithelial-to-mesenchymal transition (EMT) is important early in metastasis to enable cancer cells to detach from neighboring cells, become migratory, and escape the primary tumor. While different phases of metastasis expose cells to variable nutrient environments and demands, the metabolic requirements and plasticity of each step are uncertain. Here we show that EMT and primary tumor escape are stimulated by disrupted oxidative metabolism. Using Renal Cell Carcinoma (RCC) patient samples, we identified the mitochondrial electron transport inhibitor NDUFA4L2 as upregulated in cells undergoing EMT. Deletion of NDUFA4L2 enhanced oxidative metabolism and prevented EMT and metastasis while NDUFA4L2 overexpression enhanced these processes. Mechanistically, NDUFA4L2 suppressed oxidative phosphorylation and caused citric acid cycle intermediates to accumulate, which modified chromatin accessibility of EMT-related loci to drive primary tumor escape. The effect of impaired mitochondrial metabolism to drive EMT appeared general, as renal cell carcinoma patient tumors driven by fumarate hydratase mutations with disrupted oxidative phosphorylation were highly metastatic and also had robust EMT. These findings highlight the importance of dynamic shifts in metabolism for cell migration and metastasis, with mitochondrial impairment driving early phases of this process. Understanding mitochondrial dynamics may have important implications in both basic and translational efforts to prevent cancer deaths.

cancer biology↗

bioRxiv2022

RTEL1 and MCM10 overcome topological stress during vertebrate replication termination

Topological stress can cause replication forks to stall as they converge upon one another during termination of vertebrate DNA synthesis. However, replication forks ultimately overcome topological stress and complete DNA synthesis, suggesting that alternative mechanisms can overcome topological stress. We performed a proteomic analysis of converging replication forks that were stalled by topological stress in Xenopus egg extracts. We found that the helicase RTEL1 and the replisome protein MCM10 were highly enriched on DNA under these conditions. We show that RTEL1 normally plays a minor role during fork convergence while the role of MCM10 is normally negligible. However, RTEL1 and MCM10 both become crucially important for fork convergence under conditions of topological stress. RTEL1 and MCM10 exert non-additive effects on fork convergence and physically interact, suggesting that they function together. Furthermore, RTEL1 and MCM10 do not impact topoisomerase activity but do promote fork progression through a replication barrier. Thus, RTEL1 and MCM10 appear to play a general role in promoting progression of stalled forks, including when forks stall during termination. Overall, our data identify an alternate mechanism of termination involving RTEL1 and MCM10 that can be used to complete DNA synthesis under conditions of topological stress.

biochemistry↗

bioRxiv2021

MTHFD2 is a Metabolic Checkpoint Controlling Effector and Regulatory T Cell Fate and Function

Antigenic stimulation promotes T cells metabolic reprogramming to meet increased biosynthetic, bioenergetic, and signaling demands. We show that the one-carbon (1C) metabolism enzyme Methylenetetrahydrofolate Dehydrogenase-2 (MTHFD2) is highly expressed in inflammatory diseases and induced in activated T cells to promote proliferation and produce inflammatory cytokines. In pathogenic Th17 cells, MTHFD2 also prevented aberrant upregulation of FoxP3 and suppressive capacity. Conversely, MTHFD2-deficiency enhanced lineage stability of regulatory T (Treg) cells. Mechanistically, MTHFD2 maintained cellular 10-formyltetrahydrofolate for de novo purine synthesis and MTHFD2 inhibition led to accumulation of the intermediate 5-aminoimidazole carboxamide ribonucleotide that was associated with decreased mTORC1 signaling. MTHFD2 was also required for proper histone de-methylation in Th17 cells. Importantly, inhibiting MTHFD2 in vivo reduced disease severity in Experimental Autoimmune Encephalomyelitis and Delayed-Type Hypersensitivity. MTHFD2 induction is thus a metabolic checkpoint for pathogenic effector cells that suppresses anti-inflammatory Treg cells and is a potential therapeutic target within 1C metabolism.

immunology↗

bioRxiv2020

Glycosylation Limits Forward Trafficking of the Tetraspan Membrane Protein PMP22

Peripheral myelin protein 22 (PMP22) folds and traffics inefficiently, a phenomenon closely related to the mechanisms by which this tetraspan membrane protein causes Charcot-Marie-Tooth disease (CMTD). We report that elimination of N-glycosylation results in a 3-fold increase in the cell surface trafficking of wild type (WT) PMP22 and a 10-fold increase in trafficking of the unstable L16P disease mutant form. Studies of the interactions of PMP22 with oligosaccharyltransferases A and B as well as quantitative proteomic experiments established that critical endoplasmic reticulum (ER) quality control decisions occur earlier in the biogenesis to cell surface trafficking pathway for the L16P mutant than for WT. CRISPR knock-out cell lines for ER proteins calnexin, RER1, and UGGT1 illuminated the role of each protein in glycosylation dependent and independent surface trafficking of WT PMP22, as well as for a series of disease mutants of varying folding stabilities. One Sentence SummaryN-linked glycosylation was seen to dramatically limit the cell surface trafficking of PMP22, with some key quality control factors in PMP22 biogenesis being identified.

cell biology↗