Biology subjects

Richards, S. L.

Publications and source records attributed to Richards, S. L..

3 recordsLinked to original sources

bioRxiv2024

USP37 prevents premature disassembly of stressed replisomes by TRAIP

The E3 ubiquitin ligase TRAIP associates with the replisome and helps this molecular machine deal with replication stress. Thus, TRAIP promotes DNA inter-strand crosslink repair by triggering the disassembly of CDC45-MCM2-7-GINS (CMG) helicases that have converged on these lesions. However, disassembly of single CMGs that have stalled temporarily would be deleterious, suggesting that TRAIP must be carefully regulated. Here, we demonstrate that human cells lacking the de-ubiquitylating enzyme USP37 are hypersensitive to topoisomerase poisons and other replication stress-inducing agents. We further show that TRAIP loss rescues the hypersensitivity of USP37 knockout cells to topoisomerase inhibitors. In Xenopus egg extracts depleted of USP37, TRAIP promotes premature CMG ubiquitylation and disassembly when converging replisomes stall. Finally, guided by AlphaFold-Multimer, we discovered that binding to CDC45 mediates USP37s response to topological stress. In conclusion, we propose that USP37 protects genome stability by preventing TRAIP-dependent CMG unloading when replication stress impedes timely termination.

molecular biology↗

bioRxiv2024

Improving the application of Important Plant Areas to conserve threatened habitats: a case study of Uganda

Important Plant Areas (IPAs) are a successful method of identifying priority areas for plant conservation. Assessment of IPAs, however, often relies on criteria related to species, while incorporation of habitats has been less consistent. Using Uganda as a case study, we test the application of the threatened habitat criterion - criterion C. We identified nationally threatened habitats using Red List of Ecosystems criteria and assess, for the first time, how differing application of thresholds under criterion C can influence IPA network outcomes. Eleven threatened habitats were identified, with declines switching from predominantly forest to savanna after the mid-20th century. Significantly, we found current IPA guidance on use of Criterion C needlessly limits the number of sites that qualify as IPAs. The "five best sites" threshold is reserved for countries where quantitative data is unavailable, however, the application of the relevant thresholds to quantitative data largely generated fewer than five IPAs, comparably limiting conservation opportunities identified. We recommend, therefore, that the "five best" threshold is available for application on both qualitative and quantitative data. This will bolster the value of IPAs in conserving and restoring threatened and ecologically important habitats under the Kunming-Montreal Global Biodiversity Framework.

ecology↗

bioRxiv2023

The dCMP deaminase DCTD and the E3 ligase TOPORS are central mediators of decitabine cytotoxicity

The nucleoside decitabine (5-aza-dC) is used to treat several hematological cancers. Upon triphosphorylation and incorporation into DNA, 5-aza-dC induces covalent DNMT1 DNA-protein crosslinks (DPCs) and DNA hypomethylation. However, 5-aza-dC treatment success varies, and relapse is common. Using genome-scale CRISPR/Cas9 screens, we map factors determining 5-aza-dC susceptibility. Unexpectedly, we find that loss of the dCMP deaminase DCTD causes 5-aza-dC resistance, suggesting that 5-aza-dUMP generation underlies most 5-aza-dC cytotoxicity in wild-type cells. Combining results from a subsequent genetic screen in DCTD-deficient cells with identification of the proximal proteome of DNMT1-DPCs, we uncover the ubiquitin/SUMO1 E3 ligase, TOPORS, as a new DPC repair factor. TOPORS is recruited to DNMT1-DPCs in a SUMO-dependent manner and promotes their degradation. Our study suggests that 5-aza-dC-induced DPCs cause cytotoxicity when DPC repair is compromised, while cytotoxicity in wild-type cells arises from perturbed nucleotide metabolism and lays the foundations for the development of predictive biomarkers for decitabine treatment.

cell biology↗