Biology subjects

Geli, V.

Publications and source records attributed to Geli, V..

9 recordsLinked to original sources

bioRxiv2026

TERT drives liver tumorigenesis beyond telomere elongation

We generated two mouse models, p21/Tert and p21/TertCi, expressing either telomerase reverse transcriptase (TERT) or a catalytically inactive variant under the control of the p21 promoter. By 18-20 months of age, approximately 25% of mice from both genotypes developed liver tumors with histopathological features resembling human hepatocellular carcinoma (HCC). Whole-exome sequencing identified activating Ctnnb1 mutations and recurrent PP1 subunit alterations in p21/Tert tumors, whereas p21/TertCi tumors harbored activating HrasGln61Lys mutations associated with elevated C>A transversions. Both models exhibited chromosomal aberrations commonly observed in human HCC. Transcriptomic analyses revealed that {beta}-catenin-activated tumors recapitulated gene expression signatures of human HCC, while MAPK-mutated tumors showed profiles consistent with MAPK/ERK pathway activation. Metabolically, both genotypes demonstrated increased glycolysis and suppression of gluconeogenesis, including downregulation of FBP1, but expressed distinct NRF2 target genes. Spatial profiling further revealed reduced HNF4-positive hepatocytes across tumors, independent of Hnf4 transcription, and markedly diminished immune cell infiltration particularly in {beta}-catenin-activated tumors. Collectively, these findings uncover telomere-independent functions of TERT and identify molecular and metabolic features with potential relevance for predicting immunotherapy response.

cancer biology↗

bioRxiv2025

Non-canonical TERT function mitigates adipose tissue inflammation in obesity by modulating stem cell-macrophage communication and macrophage states

Background and aimsObesity drives adipose tissue (AT) expansion and chronic inflammation, leading to metabolic dysfunction through adipocyte hypertrophy, impaired ASPC differentiation, immune infiltration, and fibrosis. Stromal vascular remodeling prominently features expansion of Gdf15- and Trem2-expressing lipid-associated macrophages (LAMs), which respond to adipocyte stress and act as lipid scavengers to buffer excess lipids released by adipocytes. Here, we examined macrophage reprogramming in p21+/Tert and p21+/TertCi mice, which express active TERT or its catalytically inactive TERTCi mutant from the endogenous Cdkn1a promoter. ResultsFollowing HFD exposure, conditional expression of TERT or TERTCi resulted in a pronounced downregulation of p21 in macrophage subsets, accompanied by a reduction in AT inflammation. Notably, TERT and TERTCi expression reshaped the adipose-tissue macrophage (ATM) landscape depleting Trem2+ and Gdf15+ LAMs while preserving resident macrophages. This shift was accompanied by marked suppression of the Trem2 transcriptional program and down-regulation of PPAR-{gamma} and NR1H3 in LAMs and by impaired ASPC-LAM signaling pathways that normally drive LAM recruitment and activation. Proteomic profiling further showed that p21+/Tert ASPCs secreted markedly higher levels of proteins associated with non-conventional secretion, while extracellular matrix-associated factors and cytokines/chemokines including key mediators of ASPC-LAM communication such as Ccl2, C3, and Csf1 were substantially reduced. However, only p21+/Tert mice, and not p21+/TertCi mice, exhibited significant metabolic improvements, indicating that macrophage remodeling alone is insufficient to restore systemic metabolic function. Consistent with this, enhanced ASPC expansion and differentiation, supporting improved adipose-tissue remodeling, was observed exclusively in p21+/Tert obese mice. ConclusionsTERT remodels adipose tissue immunity independently of its enzymatic activity, and TERT-driven reprogramming of the ASPC secretome may emerge as a promising strategy to combat obesity-related metabolic dysfunction. HighlightsO_LIConditional expression of TERT or catalytically inactive TERTCi results in the depletion Trem2+ and Gdf15+ LAMs while preserving resident macrophages C_LIO_LITERT and TERTCi expression impairs ASPC-adipocyte/LAM communication pathways that normally drive LAM recruitment and activation. C_LIO_LIIn vitro, TERT conditional expression in ASPCs promotes non-conventional protein secretion and reduces the secretion of key mediators of ASPC-LAM communication C_LIO_LIOnly p21+/Tert mice, and not p21+/TertCi mice, exhibited enhanced ASPC expansion, improved adipose-tissue remodeling, and systemic metabolic benefits, demonstrating that macrophage remodeling alone is insufficient to restore metabolic function. C_LI

physiology↗

bioRxiv2025

Systematic yeast two-hybrid screening identifies novel functions for SET1C/COMPASS

Set1 is the catalytic subunit of SET1C or COMPASS, which methylates histone H3K4 and serves as a scaffold for the association of seven tightly bound polypeptides. We have employed yeast two-hybrid screenings to determine the interactome of Set1 and each subunit, providing a unique resource for exploring known and novel roles of the complex. Our screenings identified a multitude of potential interactors involved in chromatin regulation, DNA replication, meiotic breaks, and Ty transposition, processes previously associated with SET1C. Consistent with Set1 being an RNA-binding protein, the screens link SET1C to multiple aspects of RNA biogenesis, including pre-mRNA splicing and polyadenylation. The results reveal that several importins are candidate interactors of Set1, along with RGG motif-containing proteins, providing insights into the mechanisms by which Set1 moves between cytoplasmic and nuclear compartments. We further reveal that reconstituted SET1C interacts with the AT hook domain of the chromatin remodeler Snf2 and methylates multiple arginines within this domain. In vivo, we report that the ARTSTRGR AT-hook motif is methylated in a Set1-dependent manner revealing new interplay between lysine and arginine methylation.

molecular biology↗

bioRxiv2025

TERT prevents obesity-induced metabolic disorders by promoting adipose stem cell expansion and differentiation

Obesity is linked to limited adipose tissue (AT) remodeling capacity, leading to hypertrophic adipocytes, senescence, and inflammation. We used a mouse model expressing mTert (p21+/Tert) from the Cdkn1a locus to investigate the role of mTERT in obesity-induced metabolic disorders. Conditional expression of mTERT reduces metabolic disorders associated with obesity. In AT, this is accompanied by a decrease in the number of senescent p21-positive cells, very short telomeres, and oxidative DNA damage. Single nucleus RNA-seq data reveal TERT expression attenuates senescence induced by HFD in particular in adipose stem and progenitor cells (ASPC). We show that ASPC expansion and differentiation are promoted in p21+/Tert obese mice, thereby reducing metabolic disorders. We further report that mTERT remodels the landscape of macrophages in AT of obese mice. Strikingly, inactivation of mTERT catalytic activity in p21+/Tert (p21+/TertCi) mice suppresses the promotion of adipocyte formation, but neither affects attenuation of senescence nor macrophage remodeling. These results highlight mTERTs canonical and non-canonical functions in reducing obesity-associated metabolic disorders. Conditional expression of TERT thus appears as a potential therapeutic option for obesity.

physiology↗

bioRxiv2023

Xrs2 C-terminus mediates Tel1-dependent meiotic double-strand break interference

During meiosis, the programmed formation of DNA double-strand breaks (DSBs) by Spo11, a conserved topoisomerase II-like protein, initiates homologous recombination that leads to crossovers between homologous chromosomes, essential for accurate chromosome segregation and genome evolution. The DSB number, distribution and timing of formation are regulated during meiosis to ensure crossing over on all chromosomes and prevent genome instability. In S. cerevisiae, DSB interference suppresses the coincident formation of DSBs in neighboring hotspots through a Tel1/ATM dependent mechanism that remains unexplored. Here, we demonstrate that Tel1 is recruited to meiotic DSB hotspots and chromosomal axis sites in a DSB-dependent manner. This supports the tethered loop-axis complex (TLAC) model that postulates meiotic DSBs are formed within the chromosome axis environment. Tel1 recruitment to meiotic DSBs, DSB interference and the meiotic DNA damage checkpoint are all dependent on the C-terminal moiety of Xrs2, known to mediate Tel1-Xrs2 interaction in vegetative cells. However, mutation of the Xrs2 FxF/Y motif, known to stabilize Tel1 interaction with Xrs2, does not affect DSBs interference but abolishes the Tel1-dependent DNA damage checkpoint. Altogether, this work uncovers the dynamic association of Tel1 with meiotic chromosomes and highlights the critical role of its interaction with Xrs2 in fine-tuning both the meiotic DNA damage checkpoint and DSB interference. AUTHOR SUMMARYDuring meiosis, a special type of cell division that produces gametes, cells intentionally break their own DNA at preferred genomic sites (hotspots) to help shuffle genetic material between chromosomes. The repair process of those breaks, called homologous recombination, is crucial for genetic diversity and for ensuring chromosomes are distributed correctly to gametes. The number and location of DNA breaks are tightly controlled to prevent errors that could affect genetic stability. In the yeast model S. cerevisiae, a protein called Tel1 (the counterpart of ATM in mammals, a DNA damage sensor) helps limit the number of breaks per cell. Our research shows that Tel1 is recruited to DNA breaks and to specific chromosome structures (called axis), supporting the idea that DNA breaks happen within the axis environment. We also found that recruitment of Tel1 to DNA breaks depends on another protein, Xrs2. This interaction is crucial to limit further DNA breaks formation and to arrest cell cycle progression in response to DNA breaks. Overall, these findings shed light on Tel1 dynamics on meiotic chromosomes, and reveal how Tel1 and Xrs2 work together to maintain genetic stability during meiosis, a process essential for healthy reproduction and evolution.

molecular biology↗

bioRxiv2022

Induction of telomerase in p21-positive cells counteracts capillaries rarefaction in aging mice lung

Telomerase is required for long-term cell proliferation and linked to stem cells. This is evident in the lung where short telomeres are associated with lung dysfunction. We constructed a mouse model in which the telomerase (Tert) is expressed from the p21Cdkn1a promoter. We found that this peculiar Tert expression curb age-related emphysema and pulmonary perivascular fibrosis in old mice. In old mice lungs, such Tert expression preferentially occurs in endothelial cells where it reduces the number of senescent endothelial cells. Remarkably, we report that Tert counteracts the age-related decline in capillary density. This was associated with an increased number of Cd34+ cells identified as a subclass of capillary cells with proliferative capacity. Expression of catalytically inactive Tert neither prevents the decline of capillary density in old mice nor protects against age-related emphysema and fibrosis. These findings reveal that telomerase decreases age-decline of pulmonary functions by sustaining microvasculature regeneration and outgrowth.

molecular biology↗

bioRxiv2020

Set1-dependent H3K4 methylation becomes critical for DNA replication fork progression in response to changes in S phase dynamics in Saccharomyces cerevisiae

DNA replication is a highly regulated process that occurs in the context of chromatin structure and is sensitive to several histone post-translational modifications. In Saccharomyces cerevisiae, the histone methylase Set1 is responsible for the transcription-dependent deposition of H3K4 methylation (H3K4me) throughout the genome. Here we show that a combination of a hypomorphic replication mutation (orc5-1) with the absence of Set1 (set1{Delta}) compromises the progression through S phase, and this is associated with a large increase in DNA damage. The ensuing DNA damage checkpoint activation, in addition to that of the spindle assembly checkpoint, restricts the growth of orc5-1 set1{Delta}. Interestingly, orc5-1 set1{Delta} is sensitive to the lack of RNase H activity while a reduction of histone levels is able to counterbalance the loss of Set1. We propose that the recently described Set1-dependent mitigation of transcription-replication conflicts becomes critical for growth when the replication forks accelerate due to decreased origin firing in the orc5-1 background. Furthermore, we show that an increase of reactive oxygen species (ROS) levels, likely a consequence of the elevated DNA damage, is partly responsible for the lethality in orc5-1 set1{Delta}. Author summaryDNA replication, that ensures the duplication of the genetic material, starts at discrete sites, termed origins, before proceeding at replication forks whose progression is carefully controlled in order to avoid conflicts with the transcription of genes. In eukaryotes, DNA replication occurs in the context of chromatin, a structure in which DNA is wrapped around proteins, called histones, that are subjected to various chemical modifications. Among them, the methylation of the lysine 4 of histone H3 (H3K4) is carried out by Set1 in Saccharomyces cerevisiae, specifically at transcribed genes. We report that, when the replication fork accelerates in response to a reduction of active origins, the absence of Set1 leads to accumulation of DNA damage. Because H3K4 methylation was recently shown to slow down replication at transcribed genes, we propose that the Set1-dependent becomes crucial to limit the occurrence of conflicts between replication and transcription caused by replication fork acceleration. In agreement with this model, stabilization of transcription-dependent structures or reduction histone levels, to limit replication fork velocity, respectively exacerbates or moderates the effect of Set1 loss. Last, but not least, we show that the oxidative stress associated to DNA damage is partly responsible for cell lethality.

genetics↗

bioRxiv2020

Modeling heterogeneity of Triple-Negative Breast Cancer highlights potency of WEE1 and BCL-XL targeting

Triple-negative breast cancer (TNBC) is a highly aggressive breast cancer subtype characterized by a remarkable molecular heterogeneity. Currently, there are no effective druggable targets and advanced preclinical models of the human disease. Here, we generated a unique mouse model (MMTV-R26Met mice) of mammary tumors driven by a subtle increase in the expression of the wild-type MET receptor. MMTV-R26Met mice develop spontaneous, exclusive TNBC tumors, recapitulating primary resistance to treatment of patients. Proteomic profiling of MMTV-R26Met tumors and machine learning approach showed that the model faithfully recapitulates inter-tumoral heterogeneity of human TNBC. Further signaling network analysis highlighted potential druggable targets, of which co-targeting of WEE1 and BCL-XL synergistically killed TNBC cells and efficiently induced tumor regression. Mechanistically, BCL-XL inhibition exacerbates the dependency of TNBC cells on WEE1 function, leading to Histone H3 and phosphoS33RPA32 upregulation, RRM2 downregulation, cell cycle perturbation, mitotic catastrophe and apoptosis. Our study introduces a unique, powerful mouse model for studying TNBC formation and evolution, its heterogeneity, and for identifying efficient therapeutic targets.

cancer biology↗

bioRxiv2019

UFMylation of MRE11 is essential for telomere length and hematopoietic stem cell survival

Genetic studies using knockout mouse models provide strong evidence for the essential role of the ubiquitin-like protein UFM1 for hematopoiesis, especially erythroid development, yet its biological roles in this process are largely unknown. Here we have identified a UFL1-dependent UFMylation of the MRE11 nuclease on the K281 and K282 residues. We show that Hela cells lacking the specific UFM1 E3 ligase display severe telomere shortening. We further demonstrate either by deleting UFM1 or by mutating MRE11 UFMylation sites that preventing MRE11 UFMylation impacts its interaction with the telomere protein TRF2. However, the MRE11 function in double-strand-break repair remains intact. We validate these results in vivo by showing that Zebrafish knockouts for the genes ufl1 and ufm1 have shorter telomeres in hematopoietic cells. Here we present UFMylation has a new mechanisms of regulation for telomere length maintenance with a role in hematopoiesis. Key pointsModification of MRE11 by UFM1 regulates telomere maintenance and cell death in HSCs Scientific categoryUFMylation, telomere maintenance, hematopoietic stem cell survival.

molecular biology↗