Serine is a both a proteinogenic amino acid and the source of one-carbon units essential for de novo purine and deoxythymidine synthesis. In the canonical glucose-derived serine synthesis pathway, Homo sapiens phosphoglycerate dehydrogenase (PHGDH) catalyzes the first, rate-limiting step. Genetic loss of PHGDH is toxic towards PHGDH-overexpressing breast cancer cell lines even in the presence of exogenous serine. Here, we use a quantitative high-throughput screen to identify small molecule PHGDH inhibitors. These compounds reduce the production of glucose-derived serine in cells and suppress the growth of PHGDH-dependent cancer cells in culture and in orthotopic xenograft tumors. Surprisingly, PHGDH inhibition reduced the incorporation into nucleotides of one-carbon units from glucose-derived and exogenous serine. We conclude that glycolytic serine synthesis coordinates the use of one-carbon units from endogenous and exogenous serine in nucleotide synthesis, and suggest that one-carbon unit wasting may contribute to the efficacy of PHGDH inhibitors in vitro and in vivo.

Energy-coupling factor (ECF) transporters mediate uptake of micronutrients in prokaryotes. The transporters consist of an S-component that binds the transported substrate and an ECF module (EcfAA′T) that binds and hydrolyses ATP. The mechanism of transport is poorly understood but presumably involves an unusual step in which the membrane-embedded S-component topples over to carry the substrate across the membrane. In many ECF transporters, the S-component dissociates from the ECF module after transport. Subsequently, substrate-bound S-components out-compete the empty proteins for re-binding to the ECF module in a new round of transport. Here we present crystal structures of the folate-specific transporter ECF–FolT from Lactobacillus delbrueckii. Interaction of the ECF module with FolT stabilizes the toppled state, and simultaneously destroys the high-affinity folate-binding site, allowing substrate release into the cytosol. We hypothesize that differences in the kinetics of toppling can explain how substrate-loaded FolT out-competes apo-FolT for association with the ECF module.

Background: ABC transporter OpuA controls cell volume. Results: Anionic lipids are required for gating and efficient energy coupling of transport. Conclusion: Ionic strength and excluded volume effects act synergistically in the gating of transport. Significance: Tight coupling between substrate binding and ATP hydrolysis in ABC transporters allows the study of transmembrane signaling in nanodiscs.

Energy-coupling factor (ECF) transporters are membrane-protein complexes that mediate vitamin uptake in prokaryotes. They bind the substrate through the action of a specific integral membrane subunit (S-component) and power transport by hydrolysis of ATP in the three-subunit ECF module. Here, we have studied the binding of thiamine derivatives to ThiT, a thiamine-specific S-component. We designed and synthesized derivatives of thiamine that bind to ThiT with high affinity; this allowed us to evaluate the contribution of the functional groups to the binding affinity. We determined six crystal structures of ThiT in complex with our derivatives. The structure of the substrate-binding site in ThiT remains almost unchanged despite substantial differences in affinity. This work indicates that the structural organization of the binding site is robust and suggests that substrate release, which is required for transport, requires additional changes in conformation in ThiT that might be imposed by the ECF module.

Myelocytomatosis viral oncogene homolog (MYC) plays an important role in the regulation of many cellular processes, and its expression is tightly regulated at the level of transcription, translation, protein stability, and activity. Despite this tight regulation, MYC is overexpressed in many cancers and contributes to multiple hallmarks of cancer. In recent years, it has become clear that noncoding RNAs add a crucial additional layer to the regulation of MYC and its downstream effects. So far, twenty‐five microRNAs and eighteen long noncoding RNAs that regulate MYC have been identified. Thirty‐three miRNAs and nineteen lncRNAs are downstream effectors of MYC that contribute to the broad oncogenic role of MYC, including its effects on diverse hallmarks of cancer. In this review, we give an overview of this extensive, multilayered noncoding RNA network that exists around MYC. Current data clearly show explicit roles of crosstalk between MYC and ncRNAs to allow tumorigenesis.