Biology subjects

Vannier, J.-B.

Publications and source records attributed to Vannier, J.-B..

4 recordsLinked to original sources

bioRxiv2022

Mouse HP1γ regulates TRF1 expression and telomere stability

AimsTElomeric Repeat-containing RNA are long non-coding RNAs generated from the telomeres. TERRAs are essential for the establishment of heterochromatin marks at telomeres, which serve for the binding of Heterochromatin Protein 1 (HP1), a protein family of epigenetic modifiers involved with chromatin compaction and gene silencing. While HP1{gamma} is enriched on gene bodies of actively transcribed human and mouse genes, it is unclear if its transcriptional role is important for HP1{gamma} function in telomere cohesion and telomere maintenance. We aimed to study the effect of mouse HP1{gamma} on the transcription of telomere factors and molecules that can affect telomere maintenance. Main methodsWe investigated the telomere function of HP1{gamma} by using deficient mouse embryonic fibroblasts (MEFs) deriving from 13.5 embryonic day embryos compared to their litter mate controls. We used gene expression analysis of HP1{gamma} deficient MEFs and validated the molecular and mechanistic consequences of HP1{gamma} loss by telomere FISH, immunofluorescence, RT-qPCR and DNA-RNA Immunoprecipitation (DRIP). Key findingsLoss of HP1{gamma} in primary MEFs leads to a downregulation of various telomere and telomere-accessory transcripts, including shelterin protein TRF1. Its downregulation is associated with increased telomere replication stress and DNA damage ({gamma}H2AX), effects more profound in females. We suggest that the source for the impaired telomere maintenance is a consequence of increased telomeric DNA-RNA hybrids and TERRAs arising at and from mouse chromosomes 18 and X. SignificanceOur results suggest an important transcriptional control by mouse HP1{gamma} of various telomere factors including TRF1 protein and TERRAs that has profound consequences on telomere stability, with a potential sexually dimorphic nature.

cell biology↗

bioRxiv2020

Human SKI is a telomere-associated complex involved in DNA-RNA hybrid control and telomere stability.

Super killer (SKI) complex is a well-known cytoplasmic 3' to 5' mRNA decay complex that functions with the exosome to degrade excessive and aberrant mRNAs. Recently, SKIV2L, the 3' to 5' RNA helicase of the human SKI (hSKI) complex has been implicated in the degradation of nuclear non-coding RNAs escaping to the cytoplasm. Here, we show that hSKI is present in the nucleus, on chromatin and in particular at telomeres during the G2 cell cycle phase. In cells, SKIV2L prevents telomeric loss, and DNA damage response activation, and its absence leads to DNA-RNA hybrid-mediated telomere fragility. Moreover, we demonstrate that purified hSKI complex preferentially unwinds telomeric DNA-RNA hybrids in vitro. Taken together, our results provide a nuclear function of the hSKI complex in overcoming replication stress caused by aberrant processing of telomeric DNA-RNA hybrids and thus maintaining telomere stability.

molecular biology↗

bioRxiv2020

Visualising G-quadruplex DNA dynamics in live cells by fluorescence lifetime imaging microscopy

Guanine rich regions of oligonucleotides fold into quadruple-stranded structures called G-quadruplexes (G4). Increasing evidence suggests that these G4 structures form in vivo and play a crucial role in cellular processes. However, their direct observation in live cells remains a challenge. Here we demonstrate that a fluorescent probe (DAOTA-M2) in conjunction with Fluorescence Lifetime Imaging Microscopy (FLIM) can identify G4 within nuclei of live and fixed cells. We present a new FLIM-based cellular assay to study the interaction of non-fluorescent small molecules with G4 and apply it to a wide range of drug candidates. We also demonstrate that DAOTA-M2 can be used to study G4 stability in live cells. Reduction of FancJ and RTEL1 expression in mammalian cells increases the DAOTA-M2 lifetime and therefore suggests an increased number of G4 in these cells, implying that FancJ and RTEL1 play a role in resolving G4 structures in cellulo.

biophysics↗

bioRxiv2019

TRF1 prevents permissive DNA damage response, recombination and Break Induced Replication at telomeres

Telomeres are a significant challenge to DNA replication and are prone to replication stress and telomere fragility. The shelterin component TRF1 facilitates telomere replication but the molecular mechanism remains uncertain. By interrogating the proteomic composition of telomeres, we show that telomeres lacking TRF1 undergo protein composition reorganisation associated with a DNA damage response and chromatin remodelers. Surprisingly, TRF1 suppresses the accumulation of promyelocytic leukemia (PML) protein, BRCA1 and the SMC5/6 complex at telomeres, which is associated with increased Homologous Recombination (HR) and TERRA transcription. We uncovered a previously unappreciated role for TRF1 in the suppression of telomere recombination, dependent on SMC5 and also POLD3 dependent Break Induced Replication at telomeres. We propose that TRF1 facilitates S-phase telomeric DNA synthesis to prevent illegitimate mitotic DNA recombination and chromatin rearrangement.

cell biology↗