Commentary: HNRNPLL, a newly identified colorectal cancer metastasis suppressor, modulates alternative splicing of CD44 during epithelial-mesenchymal transition.
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ABSTRACT:
SUBMITTER: Baranwal S
PROVIDER: S-EPMC5650611 | biostudies-literature |
REPOSITORIES: biostudies-literature
Similar Datasets
Project description:The transition from naïve to activated T cells is marked by alternative splicing of pre-mRNA encoding the transmembrane phosphatase CD45. Using a short hairpin RNA interference screen, we identified heterogeneous ribonucleoprotein L-like (hnRNPLL) as a critical inducible regulator of CD45 alternative splicing. HnRNPLL was up-regulated in stimulated T cells, bound CD45 transcripts, and was both necessary and sufficient for CD45 alternative splicing. Depletion or overexpression of hnRNPLL in B and T cell lines and primary T cells resulted in reciprocal alteration of CD45RA and RO expression. Exon array analysis suggested that hnRNPLL acts as a global regulator of alternative splicing in activated T cells. Induction of hnRNPLL during hematopoietic cell activation and differentiation may allow cells to rapidly shift their transcriptomes to favor proliferation and inhibit cell death.
| S-EPMC2791692 | biostudies-literature
Project description:Melanoma is one of the most lethal forms of skin cancer because of its early metastatic spread. The variant form of CD44 (CD44v), a cell surface glycoprotein, is highly expressed on metastatic melanoma. The mechanisms of regulation of CD44 alternative splicing in melanoma and its pathogenic contributions are so far poorly understood. Here, we investigated the expression level of CD44 in a large set of melanocytic lesions at different stages. We found that the expression of CD44v8-10 and a splicing factor, U2AF2, is significantly increased during melanoma progression, whereas CD82/KAI1, a tetraspanin family of tumor suppressor, is reduced in metastatic melanoma. CD44v8-10 and U2AF2 expression levels, which are negatively correlated with CD82 levels, are markedly elevated in primary melanoma compared with dysplastic nevi and further increased in metastatic melanoma. We also showed that patients with higher CD44v8-10 and U2AF2 expression levels tended to have shorter survival. By using both in vivo and in vitro assays, we demonstrated that CD82 inhibits the production of CD44v8-10 on melanoma. Mechanistically, U2AF2 is a downstream target of CD82 and in malignant melanoma facilitates CD44v8-10 alternative splicing. U2AF2-mediated CD44 isoform switch is required for melanoma migration in vitro and lung and liver metastasis in vivo. Notably, overexpression of CD82 suppresses U2AF2 activity by inducing U2AF2 ubiquitination. In addition, our data suggested that enhancement of melanoma migration by U2AF2-dependent CD44v8-10 splicing is mediated by Src/focal adhesion kinase/RhoA activation and formation of stress fibers, as well as CD44-E-selectin binding reinforcement. These findings uncovered a hitherto unappreciated function of CD82 in severing the linkage between U2AF2-mediated CD44 alternative splicing and cancer aggressiveness, with potential prognostic and therapeutic implications in melanoma.
| S-EPMC5033661 | biostudies-literature
Project description:There is increasing evidence to suggest that splicing decisions are largely made when the nascent RNA is still associated with chromatin. Here we demonstrate that activity of histone deacetylases (HDACs) influences splice site selection. Using splicing-sensitive microarrays, we identified ∼700 genes whose splicing was altered after HDAC inhibition. We provided evidence that HDAC inhibition induced histone H4 acetylation and increased RNA Polymerase II (Pol II) processivity along an alternatively spliced element. In addition, HDAC inhibition reduced co-transcriptional association of the splicing regulator SRp40 with the target fibronectin exon. We further showed that the depletion of HDAC1 had similar effect on fibronectin alternative splicing as global HDAC inhibition. Importantly, this effect was reversed upon expression of mouse HDAC1 but not a catalytically inactive mutant. These results provide a molecular insight into a complex modulation of splicing by HDACs and chromatin modifications.
| S-EPMC3032741 | biostudies-literature
Project description:The human CD44 gene encodes multiple isoforms of a transmembrane protein that differ in their extracellular domains as a result of alternative splicing of its variable exons. Expression of CD44 is tightly regulated according to the type and physiological status of a cell, with expression of high molecular weight isoforms by inclusion of variable exons and low molecular weight isoforms containing few or no variable exons. Human CD44 variable exon 3 (v3) can follow a specific alternative splicing route different from that affecting other variable exons. Here we map and functionally describe the splicing enhancer element within CD44 exon v3 which regulates its inclusion in the final mRNA. The v3 splicing enhancer is a multisite bipartite element consisting of a tandem nonamer, the XX motif, and an heptamer, the Y motif, located centrally in the exon. Each of the three sites of this multisite enhancer partially retains its splicing enhancing capacity independently from each other in CD44 and shows full enhancing function in gene contexts different from CD44. We further demonstrate that these motifs act cooperatively as at least two motifs are needed to maintain exon inclusion. Their action is differential with respect to the splice-site target abutting v3. The first X motif acts on the 3' splice site, the second X motif acts on both splice sites (as a bidirectional exonic splicing enhancer), and the Y motif acts on the 5' splice site. We also show that the multisite v3 splicing enhancer is functional irrespective of flanking intron length and spatial organization within v3.
| S-EPMC2080591 | biostudies-literature
Project description:HnRNPLL was identified as a critical regulator of CD45 alternative splicing in a lentiviral shRNA screen. RNAi-mediated depletion of hnRNPLL eliminated the activation-induced induced transition from the CD45RA to the CD45RO isoform. HnRNPLL is induced during the process of T cell activation, raising the possibility that it regulates a broad program of alternative splicing in activated T cells. To test this possibility and to identify additional potential targets of hnRNPLL, we performed exon array analysis on RNA isolated from five cellular conditions: 1) activated peripheral CD4+ T cells, 2) peripheral CD4+ T cells infected with a control shRNA directed against GFP, 3) peripheral CD4+ T infected with an shRNA directed against hnRNPLL, 4) naïve cord blood CD4+ T cells, and 5) cord blood CD4+ T cells that had been activated with anti-CD3 and anti-CD28 for 24 hours. The RNA was hybridized to Affymetrix human exon arrays and the hybridization signals were analyzed with XRAYTM software (Biotique). Using stringent filters for non-expressed probesets, we identified 132 genes that showed significant alternative exon usage (p<0.01) in response to hnRNPLL knockdown, but not in response to shGFP infection. Of these 132 genes, 36 also showed significant alternative exon usage in response to activation of cord blood cells, which results in an approximate 5-fold increase in hnRNPLL expression. We thus conclude that induction of hnRNPLL represents a mechanism by which cells can rapidly shift their transcriptomes during the process of T cell activation. This SuperSeries is composed of the SubSeries listed below.
2008-06-20 | GSE11834 | GEO
Project description:HnRNPLL was identified as a critical regulator of CD45 alternative splicing in a lentiviral shRNA screen. RNAi-mediated depletion of hnRNPLL eliminated the activation-induced induced transition from the CD45RA to the CD45RO isoform. HnRNPLL is induced during the process of T cell activation, raising the possibility that it regulates a broad program of alternative splicing in activated T cells. To test this possibility and to identify additional potential targets of hnRNPLL, we performed exon array analysis on RNA isolated from five cellular conditions: 1) activated peripheral CD4+ T cells, 2) peripheral CD4+ T cells infected with a control shRNA directed against GFP, 3) peripheral CD4+ T infected with an shRNA directed against hnRNPLL, 4) naïve cord blood CD4+ T cells, and 5) cord blood CD4+ T cells that had been activated with anti-CD3 and anti-CD28 for 24 hours. The RNA was hybridized to Affymetrix human exon arrays and the hybridization signals were analyzed with XRAYTM software (Biotique). Using stringent filters for non-expressed probesets, we identified 132 genes that showed significant alternative exon usage (p<0.01) in response to hnRNPLL knockdown, but not in response to shGFP infection. Of these 132 genes, 36 also showed significant alternative exon usage in response to activation of cord blood cells, which results in an approximate 5-fold increase in hnRNPLL expression. We thus conclude that induction of hnRNPLL represents a mechanism by which cells can rapidly shift their transcriptomes during the process of T cell activation. This SuperSeries is composed of the following subset Series: GSE11832: naive/activated ANOVA group GSE11833: LL-sh4/uninfected/shGFP ANOVA group
2010-09-15 | E-GEOD-11834 | biostudies-arrayexpress
Project description:An epithelial to mesenchymal transition (EMT) has been shown to be a necessary precursor to prostate cancer metastasis. Additionally, the differential expression and splicing of mRNAs has been identified as a key means to distinguish epithelial from mesenchymal cells by qPCR, western blotting and immunohistochemistry. However, few markers exist to differentiate between these cells by flow cytometry. We previously developed two cell lines, PC3-Epi (epithelial) and PC3-EMT (mesenchymal). RNAseq was used to determine the differential expression of membrane proteins on PC3-Epi/EMT. We used western blotting, qPCR and flow cytometry to validate the RNAseq results. CD44 was one of six membrane proteins found to be differentially spliced between epithelial and mesenchymal PC3 cells. Although total CD44 was positive in all PC3-Epi/EMT cells, PC3-Epi cells had a higher level of CD44v6 (CD44 variant exon 6). CD44v6 was able to differentiate epithelial from mesenchymal prostate cancer cells using either flow cytometry, western blotting or qPCR.
| S-EPMC4391735 | biostudies-literature
Project description:Retention of a subset of introns in spliced polyadenylated mRNA is emerging as a frequent, unexplained finding from RNA deep sequencing in mammalian cells.Here we analyze intron retention in T lymphocytes by deep sequencing polyadenylated RNA. We show a developmentally regulated RNA-binding protein, hnRNPLL, induces retention of specific introns by sequencing RNA from T cells with an inactivating Hnrpll mutation and from B lymphocytes that physiologically downregulate Hnrpll during their differentiation. In Ptprc mRNA encoding the tyrosine phosphatase CD45, hnRNPLL induces selective retention of introns flanking exons 4 to 6; these correspond to the cassette exons containing hnRNPLL binding sites that are skipped in cells with normal, but not mutant or low, hnRNPLL. We identify similar patterns of hnRNPLL-induced differential intron retention flanking alternative exons in 14 other genes, representing novel elements of the hnRNPLL-induced splicing program in T cells. Retroviral expression of a normally spliced cDNA for one of these targets, Senp2, partially corrects the survival defect of Hnrpll-mutant T cells. We find that integrating a number of computational methods to detect genes with differentially retained introns provides a strategy to enrich for alternatively spliced exons in mammalian RNA-seq data, when complemented by RNA-seq analysis of purified cells with experimentally perturbed RNA-binding proteins.Our findings demonstrate that intron retention in mRNA is induced by specific RNA-binding proteins and suggest a biological significance for this process in marking exons that are poised for alternative splicing.
| S-EPMC4053824 | biostudies-literature
Project description:Wnt5a is a non-canonical signaling Wnt. Low expression of WNT5A is correlated with poor prognosis in breast cancer patients. The highly invasive breast cancer cell lines, MDA-MB-231 and 4T1, express very low levels of WNT5A. To determine if enhanced expression of WNT5A would affect metastatic behavior, we generated WNT5A expressing cells from the 4T1 and MDA-MB-231 parental cell lines. WNT5A expressing cells demonstrated cobblestone morphology and reduced in vitro migration relative to controls. Cell growth was not altered. Metastasis to the lung via tail vein injection was reduced in the 4T1-WNT5A expressing cells relative to 4T1-vector controls. To determine the mechanism of WNT5A action on metastasis, we performed microarray and whole-transcriptome sequence analysis (RNA-seq) to compare gene expression in 4T1-WNT5A and 4T1-vector cells. Analysis indicated highly significant alterations in expression of genes associated with cellular movement. Down-regulation of a subset of these genes, Mmp13, Nos2, Il1a, Cxcl2, and Lamb3, in WNT5A expressing cells was verified by semi-quantitative RT-PCR. Significant differences in transcript splicing were also detected in cell movement associated genes including Cd44. Cd44 is an adhesion molecule with a complex genome structure. Variable exon usage is associated with metastatic phenotype. Alternative spicing of Cd44 in WNT5A expressing cells was confirmed using RT-PCR. We conclude that WNT5A inhibits metastasis through down-regulation of multiple cell movement pathways by regulating transcript levels and splicing of key genes like Cd44.
| S-EPMC3590134 | biostudies-literature
Project description:Alternative splicing of genes is an efficient means of generating variation in protein function. Several disease states have been associated with rare genetic variants that affect splicing patterns. Conversely, splicing efficiency of some genes is known to vary between individuals without apparent ill effects. What is not clear is whether commonly observed phenotypic variation in splicing patterns, and hence potential variation in protein function, is to a significant extent determined by naturally occurring DNA sequence variation and in particular by single nucleotide polymorphisms (SNPs). In this study, we surveyed the splicing patterns of 250 exons in 22 individuals who had been previously genotyped by the International HapMap Project. We identified 70 simple cassette exon alternative splicing events in our experimental system; for six of these, we detected consistent differences in splicing pattern between individuals, with a highly significant association between splice phenotype and neighbouring SNPs. Remarkably, for five out of six of these events, the strongest correlation was found with the SNP closest to the intron-exon boundary, although the distance between these SNPs and the intron-exon boundary ranged from 2 bp to greater than 1,000 bp. Two of these SNPs were further investigated using a minigene splicing system, and in each case the SNPs were found to exert cis-acting effects on exon splicing efficiency in vitro. The functional consequences of these SNPs could not be predicted using bioinformatic algorithms. Our findings suggest that phenotypic variation in splicing patterns is determined by the presence of SNPs within flanking introns or exons. Effects on splicing may represent an important mechanism by which SNPs influence gene function.
| S-EPMC1904363 | biostudies-literature