Biology subjects

Nelson, C. B.

Publications and source records attributed to Nelson, C. B..

8 recordsLinked to original sources

bioRxiv2025

Anillin-dependent actin assembly at PML NBs protects genome stability

Nuclear filamentous actin (F-actin) is emerging as a key regulator of genome stability1-6. During replication stress, transient bursts of nuclear actin assembly in S-phase promote fork remodelling and repair3,4, but how these bursts are initiated, regulated, and whether nuclear F-actin also act on DNA lesions inherited across cell cycles, remains unknown. Here, we show that replication stress induces nuclear actin assembly at liquid-liquid phase-separated (LLPS) promyelocytic leukaemia nuclear bodies (PML NBs), driven by the actin-binding protein Anillin. Although best known as a cytokinesis factor, Anillin localises to PML NBs in interphase, where it concentrates monomeric actin (G-actin) and establishes a favourable environment for spontaneous actin assembly. Filament growth within these condensates remodels PML NB morphology and composition, releasing sequestered AKT into the nucleoplasm. AKT is subsequently phosphorylated and activated, and this nuclear AKT activity is required to regulate 53BP1 nuclear bodies in G1. These protective LLPS compartments shield under-replicated DNA inherited from the stressed S-phase until the following S-phase. This prevents premature engagement by aberrant repair pathways that would otherwise generate toxic intermediates and culminate in mitotic failure. Together, these findings define a condensate-to-filament pathway in which nuclear F-actin dynamically reorganises phase-separated compartments to safeguard genome stability across cell cycles.

cell biology↗

bioRxiv2025

Neutrophil extracellular traps offer a new therapeutic target for elephant endotheliotropic herpes hemorrhagic disease (EEHV-HD)

Elephant survival is threatened by a devastating hemorrhagic disease called elephant endotheliotropic herpes virus-hemorrhagic disease (EEHV-HD). Once clinical signs are observed in elephants, the disease progresses rapidly and frequently results in death. EEHV-HD negatively impacts elephant conservation because very young, reproductively immature elephants are most at risk for death. Ongoing efforts to understand disease pathogenesis and progression may identify treatment targets and improve clinical outcomes. In some lethal EEHV-HD cases, microthrombosis has been observed in organ tissues similar to other hemorrhagic diseases in humans and animals where sticky webs of protein-coated DNA strands called neutrophil extracellular traps (NETs) exacerbate thrombosis and hemorrhage associated with disseminated intravascular coagulation (DIC). In this study, we sought to identify if NET formation occurs in elephants and could contribute to poor outcomes in EEHV-HD. Our study demonstrated NET release for the first time from elephant heterophils (neutrophils) that occurred in response to various stimuli, including plasma from EEHV-HD affected elephants. EEHV-HD affected tissues contained extensive NETs suggesting that dysregulated NET formation contributes to pathogenesis of this disease. Importantly, elephant neutrophils were blocked from releasing NETs in response to EEHV-HD plasma using known NET inhibitors. The ability to stop NETs in EEHV-HD offers a new therapeutic approach that could be combined with current therapies to improve survival for affected elephants and to positively impact conservation efforts.

immunology↗

bioRxiv2025

Potent synthetic lethality between PLK1 and EYA-family inhibitors in tumours of the central and peripheral nervous system

The Eyes Absent family of protein phosphatases (EYA1-4) are aberrantly expressed and tumour-promoting across many devastating cancers of neurological origin affecting both children and adults. It has recently been demonstrated that EYA1 and EYA4 promote tumour cell survival by increasing the active pool of Polo-like kinase 1 (PLK1) molecules. This discovery provides a rationale for the therapeutic combination of EYA inhibitors with direct, ATP-competitive, PLK1 inhibitors. Here, we demonstrate potent and synergistic effects of EYA and PLK1 inhibition in cancer cell lines that overexpress EYA1 and/or EYA4, including in neuroblastoma and glioblastoma models. We identify decreases in PLK1 activity and RAD51 foci formation, and increases in mitotic arrest and cell death, as mechanistic contributors to combination sensitivity. Combined EYA and PLK1 inhibition is also effective in glioblastoma stem cell models that overexpress EYA1/EYA4 and specifically targets the cancer stem cell state. Finally, through multi-omic correlational analysis, we identify high levels of the NuRD complex and SOX9 as contributors to combination treatment sensitivity. Overall, this work identifies a novel synthetic lethal combination therapy with potential utility across a wide range of neurological cancers.

cancer biology↗

bioRxiv2024

Homologous recombination promotes mitotic death to suppress the innate immune response

Double strand breaks (DSBs) can initiate mitotic catastrophe, a complex oncosuppressive phenomenon characterized by cell death during or after cell division. Through single-cell analysis of extended live imaging, we unveiled how cell cycle-regulated DSB repair guides disparate mitotic catastrophe outcomes. Our data reveal that toxic double Holliday junctions (dHjs) generated during homologous recombination (HR) promote non-immunogenic intrinsic apoptosis in the immediate mitosis after S or G2-phase DSB induction. Conversely, the combined activity of non-homologous end joining (NHEJ), microhomology mediated end joining (MMEJ), and single strand annealing (SSA) enable G1 phase cells to tolerate high DSB loads at the cost of aberrant cell division, innate immune response activation and delayed extrinsic lethality. Targeting NHEJ, MMEJ, or SSA promotes HR-dependent mitotic death, while suppressing mitotic death fosters a robust immunogenic response. Together the data indicate that a temporal repair hierarchy, coupled with cumulative DSB load, serves as a reliable predictor of mitotic catastrophe outcomes. In this pathway, HR suppress the innate immune response by promoting mitotic lethality.

cell biology↗

bioRxiv2022

The Eyes Absent family members EYA4 and EYA1 promote PLK1 activation and successful mitosis through tyrosine dephosphorylation.

The Eyes Absent family of proteins (EYA1-4) are a biochemically unique group of tyrosine phosphatases known to be tumour promoting across a range of cancer types. To date, the molecular targets of EYA phosphatase activity remain largely uncharacterised. Here, we identify Polo-like kinase 1 (PLK1) as a direct interactor and phosphatase substrate of both EYA4 and EYA1, with pY445 on PLK1 being the primary target site. EYA-mediated dephosphorylation of PLK1 in the G2 phase of the cell cycle is required for centrosome maturation, PLK1 localization to centrosomes, and polo-box domain (PBD) dependent interactions between PLK1 and the PLK1-activating proteins BORA and CEP192. Molecular dynamics simulations support the rationale that pY445 confers a structural impairment to PBD-substrate interactions that is relieved by EYA-mediated dephosphorylation. Depletion of EYA4 or EYA1, or chemical inhibition of EYA phosphatase activity, dramatically reduces PLK1 activation, causing mitotic defects and cell death. Overall, we have characterized a novel phosphotyrosine signalling network governing PLK1 and mitosis. This work provides a mechanism of cell killing for EYA phosphatase inhibitors with important therapeutic implications.

cell biology↗

bioRxiv2022

Replication stress tolerance and management differs between naive and primed pluripotent cells

Replication stress is an endemic threat to genome stability. For reasons unknown, replication stress response factors become essential during peri-implantation development. This coincides with a stem cell potency switch from the naive to the primed state. Using genetically matched, chimera-derived mouse naive embryonic (mESC) and primed epiblast stem cells (mEpiSC) we found that replication stress management differs between potency states. Primed mEpiSCs rely on Atr activity to prevent replication catastrophe, minimize genomic damage, avoid apoptosis, and re-enter the cell cycle. Conversely, under replications stress, mESCs readily activate Atm regardless of Atr activity, undergo replication catastrophe, and induce apoptosis. Primed pluripotent cells therefore engage Atr to counteract replication difficulties and maintain viability, whereas cells in the naive state are more readily cleared under the same conditions. We anticipate these divergent strategies enable pluripotent cells of different potency states to meet associated proliferative or developmental demands during early development.

developmental biology↗

bioRxiv2022

Deconstructing replicative senescence heterogeneity of human mesenchymal stem cells at single cell resolution reveals therapeutically targetable senescent cell sub-populations

Cellular senescence is characterised by a state of permanent cell cycle arrest. It is accompanied by often variable release of the so-called senescence-associated secretory phenotype (SASP) factors, and occurs in response to a variety of triggers such as persistent DNA damage, telomere dysfunction, or oncogene activation. While cellular senescence is a recognised driver of organismal ageing, the extent of heterogeneity within and between different senescent cell populations remains largely unclear. Elucidating the drivers and extent of variability in cellular senescence states is important for discovering novel targeted seno-therapeutics and for overcoming cell expansion constraints in the cell therapy industry. Here we combine cell biological and single cell RNA-sequencing approaches to investigate heterogeneity of replicative senescence in human ESC-derived mesenchymal stem cells (esMSCs) as MSCs are the cell type of choice for the majority of current stem cell therapies and senescence of MSC is a recognized driver of organismal ageing. Our data identify three senescent subpopulations in the senescing esMSC population that differ in SASP, oncogene expression, and escape from senescence. Uncovering and defining this heterogeneity of senescence states in cultured human esMSCs allowed us to identify potential drug targets that may delay the emergence of senescent MSCs in vitro and perhaps in vivo in the future.

bioinformatics↗

bioRxiv2019

Telomeric Double Strand Breaks Facilitate Formation of 5’ C-Rich Overhangs in G1 Human Cells

Telomeres are repetitive nucleoprotein complexes that protect chromosomal termini and prevent them from activating an inappropriate DNA damage response (DDR). Here, we characterized the human cellular response to targeted telomeric DSBs in telomerase positive and telomerase-independent alternative lengthening of telomeres (ALT) cells, specifically in G1. Telomeric DSBs in G1 human cells elicited early signatures of a DDR, however, localization of 53BP1, an important regulator of resection at broken ends, was not observed at telomeric break sites. Consistent with this finding and previously reported repression of classical nonhomologous end-joining (c-NHEJ) at telomeres, evidence for c-NHEJ was also lacking. Likewise, no evidence of homologous recombination (HR)-dependent repair of telomeric DSBs in G1 was observed. Rather, and supportive of rapid truncation events, telomeric DSBs in G1 human cells facilitated formation of extensively resected tracks of 5 C-rich telomeric single-stranded (ss)DNA, a previously proposed marker of the recombination dependent ALT pathway. Indeed, induction of telomeric DSBs in human ALT cells also resulted in significant increases in 5 C-rich (ss)telomeric DNA in G1, which rather than RPA, were bound by the complementary telomeric RNA, TERRA. These results suggest that targeting TERRA-mediated protection at damaged telomeres may represent a promising therapeutic strategy, particularly against ALT-positive cancers.

molecular biology↗