Biology subjects

Tellier, M.

Publications and source records attributed to Tellier, M..

12 recordsLinked to original sources

bioRxiv2026

A single-nucleus multi-omic atlas of gene regulation across 21 adult human tissues

Diverse human cell types establish specialized functions through lineage- and context-specific regulatory programs. Interpreting non-coding genetic risk requires integrated multi-omic reference maps that directly connect regulatory DNA to cellular expression across human tissues. Here we present a single-nucleus multi-omic atlas comprising 459,856 transcriptomic and chromatin accessibility profiles from 21 adult human tissues and four donors, including paired measurements from 160,688 nuclei. The atlas resolves nine cell lineages, 61 broad cell types and 313 subclusters, and identifies 1,085,062 candidate cis-regulatory elements (cCREs), including 161,270 novel elements absent from ENCODE. Regulatory activity was dominated by cell identity but refined by tissue context. Joint profiling enabled 871,177 cCRE-gene associations and revealed lineage-specific regulatory architectures. Cross-tissue accessibility further identified lineage-restricted and constitutively inaccessible chromatin domains, the latter showing preferential hypomethylation across human cancers. Furthermore, we leverage this dataset to train sequence-to-function models to predict chromatin-accessibility effects for 548,656 fine-mapped variants, identifying 18,133 high-effect variants, including 1,120 broadly active variants. Models trained for eight endothelial subtypes further resolve predicted variant effects across vascular beds. Together, this atlas provides a comprehensive cellular and computational framework for interpreting regulatory sequence, context-dependent gene control, and complex trait genetics across the human body.

genomics↗

bioRxiv2024

Inhibition of SF3B1 affects recruitment of P-TEFb to chromatin through multiple mechanisms

Processing of nascent pre-mRNAs is tightly coupled to transcription by RNA polymerase II (RNAPII) through reversible phosphorylation of the polymerase and associated factors by transcriptional kinases. P-TEFb, comprising cyclin-dependent kinase (CDK)9 and cyclin T1, is a key transcription elongation kinase, which also regulates co-transcriptional splicing and mRNA cleavage and polyadenylation. Chemical inhibition of SF3B1, a component of the splicing factor U2 snRNP, decreases P-TEFb recruitment to chromatin and mirrors the effect of P-TEFb inhibition on transcription. However, the mechanism of this effect of SF3B1 inhibitors was unclear. Here we show that SF3B1 inhibition causes rapid nuclear export of P-TEFb and loss of SF3B1 phosphorylation. SF3B1 is in complex with P-TEFb on chromatin with the elongation/splicing factor HTATSF1 and the splicing factor SNW1. SF3B1 inhibition causes the nuclear export of SNW1, but not of HTATSF1. The chromatin association of AFF4, an interaction partner of P-TEFb, is also affected by SF3B1 inhibition. Surprisingly, SF3B1 inhibition promotes degradation of SRSF2, a splicing factor known to help recruit P-TEFb to chromatin. Our results indicate that SF3B1 inhibition affects P-TEFb recruitment to genes via multiple pathways. Together, these interactions ensure efficient coupling of transcription and splicing.

molecular biology↗

bioRxiv2024

NELF coordinates Pol II transcription termination and DNA replication initiation

Regulation of RNA polymerase II (Pol II) transcription is closely associated with cell proliferation. However, it remains unclear how the Pol II transcription program is altered in cancer to favour cell growth. Here, we find that gene expression of NELFCD, a known negative elongation factor, is up-regulated in colorectal tumours. To dissect the direct role of NELF-C on Pol II transcription in such cancer, we employed an auxin-dependent protein degradation system for NELF-C in combination with nascent transcript sequencing technologies. Strikingly, we demonstrated that the acute loss of NELF-C protein globally perturbs Pol II transcription termination and also increases transcription elongation rate, independently of promoter-proximal Pol II pausing. This results in Pol II transcription into DNA replication initiation zones, and may link to failure of the cell cycle transition into S phase. We anticipate that NELF will be a potential therapeutic target to restrict colorectal cancers by promoting transcription-replication conflict. HIGHLIGHTSO_LIExpression of NELFCD transcript is up-regulated in colorectal tumors C_LIO_LINELF-C protein is mandatory for the transition between G1-S phases during cell cycle C_LIO_LINELF-C loss impairs transcription termination independently of Pol II promoter-proximal pausing C_LIO_LINELF-C loss leads Pol II to invade DNA replication initiation zones C_LI

molecular biology↗

bioRxiv2023

Pro-inflammatory polarization and colorectal cancer modulate alternative and intronic polyadenylation in primary human macrophages

Macrophages are essential cells of the immune system that alter their inflammatory profile depending on their microenvironment. Alternative polyadenylation in the 3UTR (3UTR-APA) and intronic polyadenylation (IPA) are mechanisms that modulate gene expression, in particular in cancer and activated immune cells. Yet, how polarization and colorectal cancer (CRC) cells microenvironment affect 3UTR-APA and IPA in primary human macrophages remains unknown. Here, primary human monocytes were isolated from healthy donors, differentiated and polarized into a pro-inflammatory state and ChrRNA-Seq and 3RNA-Seq were performed to quantify gene expression and characterize new 3UTR-APA and IPA mRNA isoforms. Our results show that polarization of human macrophages from naive to a pro-inflammatory state causes a marked increase both in proximal polyA site selection in the 3UTR and in IPA events, in genes relevant for macrophage functions. Additionally, we found a negative correlation between differential gene expression and IPA during pro-inflammatory polarization of primary human macrophages. As macrophages are abundant immune cells in the CRC microenvironment that either promote or abrogate cancer progression, we investigated how indirect exposure to CRC cells affects macrophage gene expression and 3UTR-APA and IPA mRNA events. Co-culture with CRC cells alters the inflammatory phenotype of macrophages, increases the expression of pro-tumoral genes and induce 3UTR-APA alterations. Notably, some of these gene expression differences were also found in tumour-associated macrophages of CRC patients, indicating that they are physiological relevant. Upon macrophage pro-inflammatory polarization SRSF12 is the pre-mRNA processing gene that is most upregulated. After SRSF12 knockdown in M1 macrophages there is a global downregulation of gene expression, in particular in genes involved in gene expression regulation and in immune responses. Our results reveal new 3UTR-APA and IPA mRNA isoforms produced during pro-inflammatory polarization of primary human macrophages and CRC co-culture that may be used in the future as diagnostic or therapeutic tools.

molecular biology↗

bioRxiv2023

Differential effects of pre-mRNA splicing inhibitors on RNA polymerase II transcription

The production of eukaryotic mRNAs requires transcription by RNA polymerase (pol) II and co-transcriptional processing, including capping, splicing, and cleavage and polyadenylation. Pol II can positively affect co-transcriptional processing through interaction of factors with its carboxyl terminal domain (CTD), comprising 52 repeats of the heptapeptide Tyr1-Ser2-Pro3-Thr4-Ser5-Pro6-Ser7, and pol II elongation rate can regulate splicing. Splicing, in turn, can also affect transcriptional activity and transcription elongation defects are caused by some splicing inhibitors. Multiple small molecule inhibitors of splicing are now available, some of which specifically target SF3B1, a U2 snRNP component. SF3B1 inhibition results in a general downregulation of transcription elongation, including premature termination of transcription caused by increased use of intronic poly(A) sites. Here, we have investigated the effect of Madrasin and Isoginkgetin, two non-SF3B1 splicing inhibitors, on splicing and transcription. Surprisingly, we found that both Madrasin and Isoginkgetin affect transcription before any effect on splicing, indicating that their effect on pre-mRNA splicing is likely to be indirect. Both small molecules promote a general downregulation of transcription. Based on these and other published results, we conclude that these two small molecules should not be considered as primarily pre-mRNA splicing inhibitors.

molecular biology↗

bioRxiv2022

Cleavage of the pseudoprotease iRhom2 by the signal peptidase complex reveals an ER-to-nucleus signalling pathway

iRhoms are pseudoprotease members of the rhomboid-like superfamily and are cardinal regulators of inflammatory and growth factor signalling; they function primarily by recognising transmembrane domains of their clients. Here we report an unexpected, and mechanistically distinct, nuclear function of iRhoms. iRhom2 is a non-canonical substrate of the signal peptidase complex (SPC), the protease that removes signal peptides from secreted proteins. Cleavage of iRhom2 generates an N-terminal fragment that enters the nucleus and modifies the cellular transcriptome. We observed elevated nuclear iRhom2 in skin biopsies of patients with psoriasis and tylosis with oesophageal cancer (TOC); increased SPC-mediated iRhom2 cleavage in a psoriasis model; and overlapping transcriptional signatures between psoriasis and expression of the iRhom2 N-terminus. This work highlights the pathophysiological significance of this SPC-dependent ER-to-nucleus signalling pathway, and is the first example of a rhomboid-like protein that mediates protease-regulated nuclear signalling.

cell biology↗

bioRxiv2022

Regulation of cytoplasmic mRNA level by chromatin retention

Transcription and co-transcriptional processes, including pre-mRNA splicing and mRNA cleavage and polyadenylation, regulate the production of mature mRNAs. The carboxyl terminal domain (CTD) of RNA polymerase (pol) II, which comprises 52 repeats of the Tyr1Ser2Pro3Thr4Ser5Pro6Ser7 peptide, is involved in the coordination of transcription with co-transcriptional processes. The pol II CTD is dynamically modified by protein phosphorylation, which regulates recruitment of transcription and co-transcriptional factors. We have investigated whether cytoplasmic levels of mature mRNA from intron-containing protein-coding genes are related to pol II CTD phosphorylation, RNA stability, and pre-mRNA splicing and mRNA cleavage and polyadenylation efficiency. We find that genes that produce a low level of mature mRNA are associated with relatively high phosphorylation of the pol II CTD Tyr1 and Thr4 residues, poor RNA processing, increased chromatin retention, and shorter RNA half-life. While these poorly-processed transcripts are degraded by the nuclear RNA exosome, our results indicate that in addition to RNA half-life, chromatin retention due to a low RNA processing efficiency also plays an important role in the regulation of cytoplasmic mRNA levels.

bioinformatics↗

bioRxiv2021

R-loop homeostasis and cancer mutagenesis promoted by the DNA cytosine deaminase APOBEC3B

The single-stranded DNA cytosine-to-uracil deaminase APOBEC3B is an antiviral protein implicated in cancer. However, its substrates in cells are not fully delineated. Here, APOBEC3B proteomics reveal interactions with a surprising number of R-loop factors. Biochemical experiments show APOBEC3B binding to R-loops in human cells and in vitro. Genetic experiments demonstrate R-loop increases in cells lacking APOBEC3B and decreases in cells overexpressing APOBEC3B. Genome-wide analyses show major changes in the overall landscape of physiological and stimulus-induced R-loops with thousands of differentially altered regions as well as binding of APOBEC3B to many of these sites. APOBEC3 mutagenesis impacts overexpressed genes and splice factor mutant tumors preferentially, and APOBEC3-attributed kataegis are enriched in RTCW consistent with APOBEC3B deamination. Taken together with the fact that APOBEC3B binds single-stranded DNA and RNA and preferentially deaminates DNA, these results support a mechanism in which APOBEC3B mediates R-loop homeostasis and contributes to R-loop mutagenesis in cancer. HighlightsO_LIUnbiased proteomics link antiviral APOBEC3B to R-loop regulation C_LIO_LISystematic alterations of APOBEC3B levels trigger corresponding changes in R-loops C_LIO_LIAPOBEC3B binds R-loops in living cells and in vitro C_LIO_LIBioinformatics analyses support an R-loop deamination and mutation model C_LI

cancer biology↗

bioRxiv2021

CDK9 and PP2A regulate the link between RNA polymerase II transcription termination and RNA maturation.

AbstractCDK9 is a kinase critical for the productive transcription of protein-coding genes by RNA polymerase II (pol II). As part of P-TEFb, CDK9 phosphorylates the carboxyl-terminal domain (CTD) of pol II and elongation factors, which allows pol II to elongate past the early elongation checkpoint (EEC) encountered soon after initiation. We show that, in addition to halting pol II at the EEC, loss of CDK9 activity causes premature termination of transcription across the last exon, loss of polyadenylation factors from chromatin, and loss of polyadenylation of nascent transcripts. Inhibition of the phosphatase PP2A abrogates the premature termination and loss of polyadenylation caused by CDK9 inhibition, indicating that this kinase/phosphatase pair regulates transcription elongation and RNA processing at the end of protein-coding genes. We also confirm the splicing factor SF3B1 as a target of CDK9 and show that SF3B1 in complex with polyadenylation factors is lost from chromatin after CDK9 inhibition. These results emphasize the important roles that CDK9 plays in coupling transcription elongation and termination to RNA maturation downstream of the EEC.

molecular biology↗

bioRxiv2018

SETMAR functions in illegitimate DNA recombination and non-homologous end joining

In anthropoid primates, SETMAR is a fusion between a methyltransferase gene and a domesticated DNA transposase. SETMAR has been found to be involved in several cellular functions including regulation of gene expression, DNA integration and DNA repair. These functions are thought to be mediated through the histone methyltransferase, the DNA binding and the nuclease activities of SETMAR. To better understand the cellular roles of SETMAR, we generated several U2OS cell lines expressing either wild type SETMAR or a truncated or mutated variant. We tested these cell lines with in vivo plasmid-based assays to determine the relevance of the different domains and activities of SETMAR in DNA integration and repair. We found that expressing the SET and MAR domains, but not wild type SETMAR, partially affect DNA integration and repair. The methyltransferase activity of SETMAR is also needed for an efficient DNA repair whereas we did not observe any requirement for the putative nuclease activity of SETMAR. Overall, our data support a non-essential function for SETMAR in DNA integration and repair.

molecular biology↗

bioRxiv2018

Development of a papillation assay using constitutive promoters to find hyperactive transposases

BackgroundTransposable elements (TEs) form a diverse group of DNA sequences encoding functions for their own mobility. This ability has been exploited as a powerful tool for molecular biology and genomics techniques. However, their use is sometimes limited because their activity is auto-regulated to allow them to cohabit within their hosts without causing excessive genomic damage. To overcome these limitations, it is important to develop efficient and simple screening assays for hyperactive transposases.\n\nResultsTo widen the range of transposase expression normally accessible with inducible promoters, we have constructed a set of vectors based on constitutive promoters of different strengths. We characterized and validated our expression vectors with Hsmar1, a member of the mariner transposon family. We observed the highest rate of transposition with the weakest promoters. We went on to investigate the effects of mutations in the Hsmar1 transposase dimer interface and of covalently linking two transposase monomers in a single-chain dimer. We also tested the severity of mutations in the lineage leading to the human SETMAR gene, in which one copy of the Hsmar1 transposase has contributed a domain.\n\nConclusionsWe generated a set of vectors to provide a wide range of transposase expression which will be useful for screening libraries of transposase mutants. We also found that mutations in the Hsmar1 dimer interface provides resistance to overproduction inhibition in bacteria, which could be valuable for improving bacterial transposon mutagenesis techniques.

molecular biology↗

bioRxiv2017

The RS Domain of Human CFIm68 Plays a Key Role in Selection Between Alternative Sites of Pre-mRNA Cleavage and Polyadenylation

Many eukaryotic protein-coding genes give rise to alternative mRNA isoforms with identical protein-coding capacities but which differ in the extents of their 3{acute} untranslated regions (3{acute}UTRs), due to the usage of alternative sites of pre-mRNA cleavage and polyadenylation. By governing the presence of regulatory 3{acute}UTR sequences, this type of alternative polyadenylation (APA) can significantly influence the stability, localisation and translation efficiency of mRNA. Though a variety of molecular mechanisms for APA have been proposed, previous studies have identified a pivotal role for the multi-subunit cleavage factor I (CFIm) in this process in mammals. Here we show that, in line with previous reports, depletion of the CFIm 68 kDa subunit (CFIm68) by CRISPR/Cas9-mediated gene disruption in HEK293 cells leads to a shift towards the use of promoter-proximal poly(A) sites. Using these cells as the basis for a complementation assay, we show that CFIm68 lacking its arginine/serine-rich (RS) domain retains the ability to form a nuclear complex with other CFIm subunits, but selectively lacks the capacity to restore polyadenylation at promoter-distal sites. In addition, nanoparticle-mediated analysis indicates that the RS domain is extensively phosphorylated in vivo. Overall, these results suggest that the CFIm68 RS domain makes a key regulatory contribution to APA.

molecular biology↗