Biology subjects

Deans, A. J.

Publications and source records attributed to Deans, A. J..

7 recordsLinked to original sources

bioRxiv2026

Fanconi Anaemia E3 Ligase complex activity is regulated by a druggable metabolite binding site in FANCX

The Fanconi anaemia (FA) DNA repair pathway is an emerging target for precision cancer therapy. Using a high-throughput FANCD2-monoubiquitination assay, we identified a class of small molecules, including MSG010, that inhibit the FA E3 ligase complex in vitro. Because these molecules, and the metabolite, palmitoyl-CoA, are known to engage allosteric drug and metabolite (ADaM) binding site in AMP-activated kinase (AMPK), we hypothesised that a similar pocket exists within the FA complex. Supporting this, long-chain, but not short-chain, fatty acyl-CoA molecules inhibited the FA E3 ligase complex activity, and sequence analysis revealed similarity between the AMPK ADaM site and a WD40 repeat in the FA subunit FANCX. Targeted mutagenesis of this FANCX region disrupted E3 ligase activity or abolished inhibition by MSG010, suggesting the presence of an ADaM-like site in FANCX. Moreover, MSG010 preferentially killed BRCA1-deficient cells in vitro. These findings identify a putative small-molecule binding site in the FA pathway that may be developed further to test for exploitation as anticancer therapeutics.

cancer biology↗

bioRxiv2024

Improved gene targeting in vivo using EoHR, a small molecule inhibitor of 53BP1

Precise genome editing by programmable nucleases such as Cas9 has revolutionised medical research by enabling the creation of gene-edited or knock-in mouse models of disease. However, a major limitation of the approach is the inefficient process of homology driven recombination (HDR) from an exogenous DNA repair template. This is because error-prone, 53BP1-dependent non-homologous end joining (NHEJ) predominates at Cas9-induced double strand breaks (DSBs). Here we report the validation of a cell-permeable and non-toxic inhibitor of 53BP1 called EoHR. In vitro, EoHR prevents 53BP1 binding to dimethylated lysine 20 on histone H4, a marker of DSBs. In cells, EoHR prevents localisation of 53BP1 at nuclease mediated DSBs and promotes HDR at a Cas9-induced break. When tested in vivo during mouse Cas9-mediated gene editing, inclusion of EoHR at the time of microinjection more than doubled the recovery of correctly edited mice and halved the time to project success. Our work shows that inhibition of 53BP by EoHR is a simple and robust way to increase HDR at Cas9 breaks that can also dramatically increase the success rates of animal model generation.

biochemistry↗

bioRxiv2024

Mechanism of structure-specific DNA binding by the FANCM branchpoint translocase

FANCM is a DNA repair protein that recognizes stalled replication forks, and recruits downstream repair factors. FANCM activity is also essential for the survival of cancer cells that utilize the Alternative Lengthening of Telomeres (ALT) mechanism. FANCM efficiently recognizes stalled replication forks in the genome or at telomeres through its strong affinity for branched DNA structures. In this study, we demonstrate that the N-terminal translocase domain drives this specific branched DNA recognition. The Hel2i subdomain within the translocase is crucial for effective substrate engagement and couples DNA binding to catalytic ATP-dependent branch migration. Removal of Hel2i or mutation of key DNA-binding residues within this domain diminished FANCMs affinity for junction DNA and abolished branch migration activity. Importantly, these mutant FANCM variants failed to rescue the cell cycle arrest, telomere-associated replication stress, or lethality of ALT-positive cancer cells depleted of endogenous FANCM. Our results reveal the Hel2i domain is key for FANCM to properly engage DNA substrates, and therefore plays an essential role in its tumour-suppressive functions by restraining the hyperactivation of the ALT pathway.

biochemistry↗

bioRxiv2022

Fancm regulates meiotic double-strand break repair pathway choice in mammals

Meiotic crossovers are required for accurate chromosome segregation and to produce new allelic combinations. Meiotic crossover numbers are tightly regulated within a narrow range, despite an excess of initiating DNA double-strand breaks. Here, we describe the tumour suppressor FANCM as a meiotic anti-crossover factor in mammals. Crossover analyses with single-gamete and pedigree datasets both reveal a genome-wide increase in crossover frequencies in Fancm-deficient mice. Gametogenesis is heavily perturbed in Fancm loss of function mice, which is consistent with the reproductive defects reported in humans with biallelic FANCM mutations. A portion of the gametogenesis defects can be attributed to the cGAS-STING pathway. Despite the gametogenesis phenotypes in Fancm mutants both sexes were capable of producing offspring. We propose that the anti-crossover function and role in gametogenesis of Fancm are separable and will inform diagnostic pathways for human genomic instability disorders.

genetics↗

bioRxiv2019

Monoubiquitination by the Fanconi Anemia core complex locks FANCI:FANCD2 on DNA in filamentous arrays

FANCI:FANCD2 monoubiquitination is a critical event for replication fork stabilization by the Fanconi anemia (FA) DNA repair pathway. It has been proposed that at stalled replication forks, monoubiquitinated-FANCD2 serves to recruit DNA repair proteins that contain ubiquitin-binding motifs. Here we have reconstituted the FA pathway in vitro to study functional consequences of FANCI:FANCD2 monoubiquitination. We report that monoubiquitination does not promote any specific exogenous protein:protein interactions, but instead stabilizes FANCI:FANCD2 heterodimers on dsDNA. This locking of FANCI:FANCD2 complex on DNA requires monoubiquitination of only the FANCD2 subunit. We further show that purified monoubiquitinated FANCI:FANCD2 forms filament-like arrays on long dsDNA using electron microscopy. Our results reveal how monoubiquitinated FANCI:FANCD2 is activated upon DNA binding and present new insights to potentially modulate monoubiquitinated FANCI:FANCD2/DNA filaments in FA cells.

biochemistry↗

bioRxiv2019

Clinical severity in Fanconi anemia correlates with residual function of FANCB missense variants

Fanconi anemia (FA) is the most common genetic cause of bone marrow failure, and is caused by inherited pathogenic variants in any of 22 genes. Of these, only FANCB is X-linked. We describe a cohort of 19 children with FANCB variants, from 16 families of the International Fanconi Anemia Registry (IFAR). Those with FANCB deletion or truncation demonstrate earlier than average onset of bone marrow failure, and more severe congenital abnormalities compared to a large series of FA individuals in the published reports. This reflects the indispensable role of FANCB protein in the enzymatic activation of FANCD2 monoubiquitination, an essential step in the repair of DNA interstrand crosslinks. For FANCB missense variants, more variable severity is associated with the extent of residual FANCD2 monoubiquitination activity. We used transcript analysis, genetic complementation, and biochemical reconstitution of FANCD2 monoubiquitination to determine the pathogenicity of each variant. Aberrant splicing and transcript destabilization was associated with two missence variants. Individuals carrying missense variants with drastically reduced FANCD2 monoubiquitination in biochemical and/or cell-based assays showed earlier onset of hematologic disease and shorter survival. Conversely, variants with near-normal FANCD2 monoubiquitination were associated with more favorable outcome. Our study reveals a genotype-phenotype correlation within the FA-B complementation group of FA, where severity is linked to the extent of residual FANCD2 monoubiquitination.\n\nKEY POINTSO_LIX-linked FANCB pathogenic variants predominantly cause acute, early onset bone marrow failure and severe congenital abnormalities\nC_LIO_LIBiochemical and cell-based assays with patient variants reveal functional properties of FANCB that associate with clinical severity\nC_LI

molecular biology↗

bioRxiv2018

FANCM-family branchpoint translocases remove co-transcriptional R-loops

Co-transcriptional R-loops arise from physiological or aberrant stalling of RNA polymerase, leading to formation of stable DNA:RNA hybrids. Unresolved R-loops can promote genome instability. Here, we show that the Fanconi anemia- and breast cancer-associated FANCM protein can directly unwind DNA-RNA hybrids from co-transcriptional R-loops in vitro. FANCM processively unwinds both short and long R-loops, irrespective of sequence, topology or coating by replication protein A. R-loops can also be unwound in the same assay by the yeast and bacterial orthologs of FANCM, Mph1 and RecG, indicating an evolutionary conserved function. Consistent with this biochemical activity of FANCM, we show that FANCM deficient cells are sensitive to drugs that stabilize R-loop formation. Our work reveals a mechanistic basis for R-loop metabolism that is critical for genome stability.

biochemistry↗