Alternative promoters (APs) occur in >30% protein-coding genes and contribute to proteome diversity. However, large-scale analyses of AP regulation are lacking, and little is known about their potential physiopathologic significance. To better understand the transcriptomic impact of estrogens, which play a major role in breast cancer, we analyzed gene and AP regulation by estradiol in MCF7 cells using pan-genomic exon arrays. We thereby identified novel estrogen-regulated genes, and determined the regulation of AP-encoded transcripts in 150 regulated genes. In <30% cases, APs were regulated in a similar manner by estradiol, while in >70% cases, they were regulated differentially. The patterns of AP regulation correlated with the patterns of estrogen receptor (ER) and CCCTC-binding factor (CTCF) binding sites at regulated gene loci. Interestingly, among genes with differentially regulated APs, we identified cases where estradiol regulated APs in an opposite manner, sometimes without affecting global gene expression levels. This promoter switch was mediated by the DDX5/DDX17 family of ER coregulators. Finally, genes with differentially regulated promoters were preferentially involved in specific processes (e.g., cell structure and motility, and cell cycle). We show in particular that isoforms encoded by the NET1 gene APs, which are inversely regulated by estradiol, play distinct roles in cell adhesion and cell cycle regulation, and that their expression is differentially associated with prognosis in ER+ breast cancer. Altogether, this study identifies the patterns of AP regulation in estrogen-regulated genes, demonstrates the contribution of AP-encoded isoforms to the estradiol-regulated transcriptome, as well as their physiopathologic significance in breast cancer.
Estrogen regulation and physiopathologic significance of alternative promoters in breast cancer.
Disease, Disease stage, Cell line, Time
View SamplesAlternative 3-terminal exons, which use intronic polyadenylation sites, are generally unconserved and lowly expressed, while the main gene products end in the last exon of genes. In this study, we discover a class of human genes, where the last exon appeared recently during evolution, and the major gene product uses an alternative 3-terminal exon corresponding to the ancestral last exon of the gene. This novel class of alternative 3-terminal exons are down-regulated on a large scale by doxorubicin, a cytostatic drug targeting topoisomerase II, and play a role in cell cycle regulation, including centromere-kinetochore assembly. The RNA-binding protein, HuR/ELAVL1 is a major regulator of this specific set of alternative 3-terminal exons. HuR binding to the alternative 3-terminal exon in the pre-messenger RNA promotes its splicing, and is reduced by topoisomerase inhibitors. These findings provide new insights into the evolution, function and molecular regulation of alternative 3-terminal exons.
A recently evolved class of alternative 3'-terminal exons involved in cell cycle regulation by topoisomerase inhibitors.
Cell line
View SamplesPre-mRNA splicing is functionally coupled to transcription, and genotoxic stresses can enhance alternative exon inclusion by affecting elongating RNA polymerase II. We report here that various genotoxic stress inducers, including camptothecin, inhibit the interaction between EWS, an RNA polymerase II-associated factor, and YB-1, a spliceosome-associated factor. This results in the cotranscriptional skipping of several exons of the MDM2 gene encoding the main p53 ubiquitin-ligase. This reversible exon skipping participates in the timely regulation of MDM2 expression, and may contribute to the accumulation of p53 during stress exposure and its rapid shut off when stress is removed. Finally, a splicing-sensitive microarray identified numerous exons that are skipped in response to camptothecin and EWS/YB-1 depletion. These data demonstrate genotoxic stress-induced alteration of the communication between the transcriptional and splicing machineries, resulting in widespread exon skipping and playing a central role in the genotoxic stress response.
Cotranscriptional exon skipping in the genotoxic stress response.
Specimen part, Cell line
View SamplesRNA helicases DDX5 and DDX17 are members of a large family of highly conserved proteins involved in gene expression regulation, although their in vivo targets and activities in biological processes like cell differentiation, that requires reprogramming of gene expression programs at multiple levels, are not well characterized. In this report, we uncovered a new mechanism by which DDX5 and DDX17 cooperate with hnRNP H/F splicing factors to define epithelial- and myoblast-specific splicing subprograms. We next observed that downregulation of DDX5 and DDX17 protein expression during epithelial to mesenchymal transdifferentiation and during myogenesis contributes to switching splicing programs during these processes. Remarkably, this downregulation is mediated by the production of microRNAs induced upon differentiation in a DDX5/DDX17-dependent manner. Since DDX5 and DDX17 also function as coregulators of master transcriptional regulators of differentiation, we propose to name these proteins master orchestrators of differentiation, that dynamically orchestrate several layers of gene expression.
RNA helicases DDX5 and DDX17 dynamically orchestrate transcription, miRNA, and splicing programs in cell differentiation.
Specimen part, Cell line
View Samples5-Fluorouracil (5-FU) is a widely used chemotherapeutic drug in colorectal cancer. Previous studies showed that 5-FU modulates RNA metabolism and mRNA expression. In addition, it has been reported that 5-FU incorporates into the RNAs constituting the translational machinery and that 5-FU affects the amount of some mRNAs associated with ribosomes. However, the impact of 5-FU on translational regulation remains unclear. Using translatome profiling, we report that a clinically relevant dose of 5-FU induces a translational reprogramming in colorectal cancer cell lines. Comparison of mRNA distribution between polysomal and non-polysomal fractions in response to 5-FU treatment using microarray quantification identified 313 genes whose translation was selectively regulated. These regulations were mostly stimulatory (91%). Among these genes, we showed that 5-FU increases the mRNA translation of HIVEP2, which encodes a transcription factor whose translation in normal condition is known to be inhibited by mir-155. In response to 5-FU, the expression of mir-155 decreases thus stimulating the translation of HIVEP2 mRNA. Interestingly, the 5-FU-induced increase in specific mRNA translation was associated with reduction of global protein synthesis. Altogether, these findings indicate that 5-FU promotes a translational reprogramming leading to the increased translation of a subset of mRNAs that involves at least for some of them, miRNA-dependent mechanisms. This study supports a still poorly evaluated role of translational control in drug response.
Translational reprogramming of colorectal cancer cells induced by 5-fluorouracil through a miRNA-dependent mechanism.
Treatment
View SamplesHuman mononuclear phagocytes comprise phenotypically and functionally overlapping subsets of dendritic cells (DC) and monocytes, but their identification remains elusive. By integrating high-dimensional single-cell protein and RNA expression data, we clearly delineated monocytes from conventional DC2 (cDC2), identifying new markers including CD88/CD89 for monocytes and HLA-DQ/Fc?RI? for cDC2, allowing their unambiguous characterization in blood and tissues. We also show that cDC2 can be subdivided into phenotypically and functionally distinct subsets based on CD5, CD163 and CD14 expression, including a unique subset of circulating inflammatory CD5-CD163+CD14+ cells related to previously defined DC3. These inflammatory DC3 were expanded in systemic lupus erythematosus patients, correlating with disease activity. Unravelling the heterogeneity of DC sub-populations in health and disease paves the way for specific DC subset-targeting therapies. Overall design: Indexed single cell RNAseq (scRNAseq) of human peripheral blood dendritic cells and monocytes
Single-Cell Analysis of Human Mononuclear Phagocytes Reveals Subset-Defining Markers and Identifies Circulating Inflammatory Dendritic Cells.
Specimen part, Subject
View SamplesA significant proportion of patients with oestrogen receptor (ER) positive breast cancers (BC) develop resistance to endocrine treatments (ET) and relapse with metastatic disease. Bone is the most common metastatic site in ER+ patients, however bone metastases are technically challenging to biopsy and analyse. Difficulties concern both tumour tissue acquisition and techniques for analysis and RNA extractions. Patient-derived xenografts (PDX) of BC bone metastases have not been reported yet. For the first time we established PDX models from bone metastatic biopsies of patients progressing on ET and treated by vertebroplasty. PDX models were analysed at transcriptomic level and compared to patient’s early primary tumours to identify new therapeutic targets associated with endocrine resistance in the metastatic setting.
PLK1 inhibition exhibits strong anti-tumoral activity in CCND1-driven breast cancer metastases with acquired palbociclib resistance.
Disease, Disease stage, Treatment
View SamplesDendritic cells (DC) are professional antigen-presenting cells that orchestrate immune responses. The human DC population comprises two main functionally-specialized lineages, whose origins and differentiation pathways remain incompletely defined. Here we combine two high-dimensional technologies — single-cell mRNA sequencing and Cytometry by Time-of-Flight (CyTOF), to identify human blood CD123+CD33+CD45RA+ DC precursors (pre-DC). Pre-DC share surface markers with plasmacytoid DC (pDC) but have distinct functional properties that were previously attributed to pDC. Tracing the differentiation of DC from the bone marrow to the peripheral blood revealed that the pre-DC compartment contains distinct lineage-committed sub-populations including one early uncommitted CD123high pre-DC subset and two CD45RA+CD123low lineage-committed subsets exhibiting functional differences. The discovery of multiple committed pre-DC populations opens promising new avenues for the therapeutic exploitation of DC subset-specific targeting. Overall design: Single cell mRNA sequencing was used to investigate the transcriptomic relationships within the dendritic cell precursors within the peripheral blood.
Mapping the human DC lineage through the integration of high-dimensional techniques.
Specimen part, Subject
View SamplesDendritic cells (DC) are professional antigen-presenting cells that orchestrate immune responses. The human DC population comprises two main functionally-specialized lineages, whose origins and differentiation pathways remain incompletely defined. Here we combine two high-dimensional technologies — single-cell mRNA sequencing and Cytometry by Time-of-Flight (CyTOF), to identify human blood CD123+CD33+CD45RA+ DC precursors (pre-DC). Pre-DC share surface markers with plasmacytoid DC (pDC) but have distinct functional properties that were previously attributed to pDC. Tracing the differentiation of DC from the bone marrow to the peripheral blood revealed that the pre-DC compartment contains distinct lineage-committed sub-populations including one early uncommitted CD123high pre-DC subset and two CD45RA+CD123low lineage-committed subsets exhibiting functional differences. The discovery of multiple committed pre-DC populations opens promising new avenues for the therapeutic exploitation of DC subset-specific targeting. Overall design: single-cell RNA Seq of human dendritic cells
Mapping the human DC lineage through the integration of high-dimensional techniques.
Specimen part, Subject
View SamplesPurpose: This study was carried out to determine the consequences of the Rfx2-/- genotype on spermatogenesis in the mouse Methods: RNA was extracted from decapsulated testes of 21 day old mixed background mice of either genotype. Deep sequencing was used to determine quantitative expression of the genomes from independent replicates of each genotype Results: RNA-Seq analysis identified some 105 genes that are down regulated at least 2-fold in Rfx2-/- testes, with ~50 being reduced at least 10-fold Conclusion: Spermatogenesis undergoes complete arrest just prior to the end of the round spermatid period of sperm development in mutant mice. Sequencing results showed that approximately 105 genes were downregulated 2 fold or more in the testes of mutant mice. Comparison of similar studies of targeted mutations in genes for other transcription factor demonstrate that Rfx2 has a large and nearly unique set of genes that depend on it directly or indirectly. A large number of downregulated genes are identified with cilia function. Overall design: Testicular mRNA profiles were determined by deep sequencing using testes from 5 independent wild type and 6 independent Rfx2-/- mice
RFX2 Is a Major Transcriptional Regulator of Spermiogenesis.
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