Cytokeratin 18 regulates the transcription and alternative splicing of apoptotic?related genes and pathways in HeLa cells.
ABSTRACT: Cytokeratin 18 (CK18), one of the major components of intermediate filaments (IF) in simple epithelial cells, undergoes caspase?mediated cleavage upon epithelial cell necrosis and apoptosis. CK18 has been used as a biomarker of several cancers and has been reported to be dysregulated in cervical cancers. The effects of dysregulated expression of CK18 at a molecular level are, however, unclear. In the present study, the function of CK18 in HeLa cells, a cell line derived from a cervical cancer cells, was investigated using shRNA knockdown. Reduced levels of CK18 led to a significant decrease in cell apoptosis, compared with control cells. Notably, RNA?seq analysis of the transcriptomes of HeLa cells, with or without CK18 knockdown, revealed that genes in the NF??B pathway, and certain apoptosis pathways, were under global transcriptional and alternative splicing regulation. Quantitative RT?PCR confirmed the CK18?regulated transcription of apoptotic genes FAS and FADD, as well as immune genes CXCL2 and CD79B, in addition to alternative splicing of FAS and CTNNB1. Western blot analysis further revealed that CK18 knockdown led to reduced expression of CASP8. In conclusion, the present study indicated that CK18 played a role in apoptosis, which may be mediated via a feed?back regulation loop and may involve regulation of transcription and alternative splicing of a number of genes in apoptotic pathways.
Project description:Cytokeratin 18(CK18), one of the major components of intermediate filaments (IF) in simple-type epithelial cells, has been used as the biomarker of several cancers. CK18 has been also reported to be dysregulated in cervical cancers, however, the precise molecular pathways regulated by CK18 remained elusive. In this study, CK18 was knockdown in Hela cells and which led to a significantly decrease of cell apoptosis compared with control cells. The global transcript profile and alternative splicing of CK18 knockdown cells and control were analyzed. A total of 593 differentially expressed genes were identified, and these genes were mainly involved in synaptic transmission, immune response, innate immune response, signal transduction pathways. Strikingly, hundreds of genes were regulated by CK18, which mainly enriched in immune and apoptosis related pathways. In conclusion, our study indicates that CK18 plays important regulatory role in cervical cancers in transcriptional level as well as alternative splicing regulation. Overall design: transcrptional analysis of CK18 knockdown and control in Hela cells
Project description:Post?transcriptional mechanisms are an important approach in the treatment of cancer, and may also be hijacked by tumor cells to help adapt to the local microenvironment. Filamin B (FLNB), an actin?binding protein that provides crucial scaffolds for cell motility and signaling, has also been identified as an RNA?binding protein. Recent studies demonstrated that FLNB might play an important role, not only in skeletal development, but also in regulating tumorigenesis; however, the effects of dysregulated expression of FLNB at the molecular level are not clear. In the present study, RNA?sequencing was performed to analyze changes in overall transcriptional and alternative splicing between the knocked?down FLNB and the control in HeLa cells. Decreased FLNB levels resulted in significantly lower apoptosis compared with control cells. FLNB knockdown extensively regulated the expression of genes in cell apoptosis, tumorigenesis, metastases, transmembrane transport and cartilage development. Moreover, FLNB regulated alternative splicing of a large number of genes involved in 'cell death' and the 'apoptotic process'. Some genes and alternative splicing related to skeletal development were enriched and regulated by FLNB. Reverse transcription?quantitative?PCR identified FLNB?regulated transcription and alternative splicing of genes, such as NLR family apoptosis inhibitory protein, interleukin 23 subunit ?, metastasis associated lung adenocarcinoma transcript 1, phosphofurin acidic cluster sorting protein 2, bone morphogenetic protein 7, matrix metallopeptidase 13, collagen type II ? 1 chain, fibroblast growth factor receptor 2 and vitamin D receptor. The present study is the first study, to the best of the authors' knowledge, to provide transcriptome?wide analysis of differential gene expression and alternative splicing upon FLNB silencing. The present results suggested that FLNB may play an important regulatory role in cervical cancer cell apoptosis via regulation of transcription and alternative splicing, which provide insight for the current understanding of the mechanisms of FLNB?mediated gene regulation.
Project description:PURPOSE:Cervical cancer is one of the most fatal diseases among women in under-developed countries. To improve cervical cancer treatment, discovery of new targets is needed. In this study, we investigated the expression of NUP210, miR-22, and Fas in cervical cancer tissues and their functions in cell cycle regulation. MATERIALS AND METHODS:We detected and compared the expression levels of NUP210, miR-22, and Fas in cervical cancer tissues with paired normal tissues using immunohistochemistry, Western blot, and real-time quantitative polymerase chain reaction. NUP210 was knocked down in HeLa cells via lentivirus, followed by cell cycle and proliferation analysis. Using a luciferase reporter assay, we explored the link between miR-22 and NUP210. We overexpressed miR-22 in HeLa cells and analyzed cell cycle and proliferation function. We then overexpressed miR-22 in NUP210 knockdown cells to explore the connection between Fas and miR-22-NUP210 signaling. RESULTS:We found that NUP210 was overexpressed in cervical cancer patients. Knocking down NUP210 restored cell apoptosis and proliferation. We confirmed miR-22 as a regulator of NUP210 and verified that miR-22 was inhibited in cervical cancer development. We also found that restoring miR-22 expression could induce cell apoptosis. Finally, we found that miR-22-regulated expression of NUP210 could alter Fas expression and, in turn, elicit cell cycle arrest and proliferation. CONCLUSION:miR-22 in cervical cancer is downregulated, resulting in NUP210 overexpression and inhibition of Fas-induced cell apoptosis.
Project description:T-cell intracellular antigen (TIA)-proteins are known regulators of alternative pre-mRNA splicing. In this study, pull-down experiments and mass spectrometry indicate that TIAR/TIAL1 and hnRNP C1/C2 are associated in HeLa nuclear extracts. Co-immunoprecipitation and GST-pull-down assays confirmed this interaction. Interestingly, binding requires the glutamine-rich (Q-rich) C-terminal domain of TIAR and the leucine-rich plus acidic residues-rich C-terminal domains of hnRNP C1/C2. This interaction also occurs in an RNA-dependent manner. Recombinant GFP-TIAR and RFP-hnRNP C1 proteins display partial nuclear co-localization when overexpressed in HeLa cells, and this requires the Q-rich domain of TIAR. hnRNP C1 overexpression in the presence of rate-limiting amounts of TIAR in HeLa and HEK293 cells affects alternative splicing of Fas and FGFR2 minigenes, promoting Fas exon 6 and FGFR2 exon K-SAM skipping, respectively. The repressor activity of hnRNP C1 on Fas exon 6 splicing is mediated by Hu antigen R (HuR). Experiments involving tethering approaches showed that the repressor capacity of hnRNP C1 is associated with an exonic splicing silencer in Fas exon 6. This effect was reversed by splice-site strengthening and is linked to its basic leucine zipper-like motif. These results suggest that hnRNP C1/C2 acts as a bridge between HuR and TIAR to modulate alternative Fas splicing.
Project description:CRKL adaptor protein was demonstrated to have important effects in various types of human cancer and contributes to malignant cell growth and chemoresistance as an overexpressed oncoprotein in cervical carcinoma. But the special molecular mechanisms of CRKL in cervical cancer remain unknown. Here we reported that CRKL regulates genes in cervical cancer related pathways via targeting alternative splicing. We analyzed the expression level of CRKL in 300 cervical cancer tissue samples available in TCGA database, showing a significant increase expression in Stage I cancer samples. From these tumor samples, we selected 40 cancer samples with 20 showing high CRKL expression and 20 showing low, which were analyzed for the potential impact of CRKL on alternative splicing regulation of cancer transcriptome. We further explored the potential function of CRKL in promoting cell proliferation and regulating alternative splicing in HeLa cells using shRNA to knock-down CRKL expression. More importantly, we showed that 34 (94%) of CRKL-regulated alternative splicing events detected in HeLa cells could be validated by qPCR approach and more than a half of these validated events detected in HeLa cells were also correlated with the CRKL expression level in cervical cancers. These results together support a conclusion that CRKL adaptor protein extensively regulates alternative splicing of many genes which are important in tumorigenesis and cancer progression, which expands the functional importance of signaling adaptors in coordinating the dynamic activation of signaling pathways with cellular responses at the alternative splicing level. Overall design: transcrptional analysis of CRKL knockdown and control in Hela cells
Project description:In multicellular organisms, cell growth and differentiation is controlled in part by programmed cell death or apoptosis. One major apoptotic pathway is triggered by Fas receptor (Fas)-Fas ligand (FasL) interaction. Neoplastic cells are frequently resistant to Fas-mediated apoptosis, evade Fas signals through down regulation of Fas and produce soluble Fas proteins that bind FasL thereby blocking apoptosis. Soluble Fas (sFas) is an alternative splice product of Fas pre-mRNA, commonly created by exclusion of transmembrane spanning sequences encoded within exon 6 (Fas?Ex6). Long non-coding RNAs (lncRNAs) interact with other RNAs, DNA, and proteins to regulate gene expression. One lncRNA, Fas-antisense or Saf, was shown to participate in alternative splicing of Fas pre-mRNA through unknown mechanisms. We show that Saf is localized in the nucleus where it interacts with Fas receptor pre-mRNA and human splicing factor 45 (SPF45) to facilitate alternative splicing and exclusion of exon 6. The product is a soluble Fas protein that protects cells against FasL-induced apoptosis. Collectively, these studies reveal a novel mechanism to modulate this critical cell death program by an lncRNA and its protein partner.
Project description:Fas is a transmembrane cell surface protein recognized by Fas ligand (FasL). When FasL binds to Fas, the target cells undergo apoptosis. A soluble Fas molecule that lacks the transmembrane domain is produced from skipping of exon 6 encoding this region in alternative splicing procedure. The soluble Fas molecule has the opposite function of intact Fas molecule, protecting cells from apoptosis. Here we show that knockdown of hnRNP A1 promotes exon 6 skipping of Fas pre-mRNA, whereas overexpression of hnRNP A1 reduces exon 6 skipping. Based on the bioinformatics approach, we have hypothesized that hnRNP A1 functions through interrupting 5' splice site selection of exon 5 by interacting with its potential binding site close to 5' splice site of exon 5. Consistent with our hypothesis, we demonstrate that mutations of the hnRNP A1 binding site on exon 5 disrupted the effects of hnRNP A1 on exon 6 inclusion. RNA pull-down assay and then western blot analysis with hnRNP A1 antibody prove that hnRNP A1 contacts the potential binding site RNA sequence on exon 5 but not the mutant sequence. In addition, we show that the mutation of 5' splice site on exon 5 to a less conserved sequence destructed the effects of hnRNP A1 on exon 6 inclusion. Therefore we conclude that hnRNP A1 interacts with exon 5 to promote distal exon 6 inclusion of Fas pre-mRNA. Our study reveals a novel alternative splicing mechanism of Fas pre-mRNA.
Project description:Post-transcriptional mechanisms is an important means for the body to fight against cancer, and it may also be hijacked by tumor cells to help them adapt to local microenvironment. Filamin B (FLNB), an actin-binding protein and providing crucial scaffolds for cell motility and signaling, was also identified as one of RNA binding proteins (RBPs). Recent works showed that FLNB might play important role not only in skeletal development but also in the regulation of tumorigenesis. However, the effects of dysregulated expression of FLNB at a molecular level are unclear. In this study, we used RNA-seq to analyze the global transcriptional level changes and alternative splicing between the knocked-down FLNB and the control in Hela cells. Reduced levels of FLNB led to a significant decrease in cell apoptosis, compared with control cells. FLNB knockdown extensively regulated the expression of genes in cell apoptosis, tumorigenesis, metastases, transmembrane transport, cartilage and nerve development. Moreover, FLNB regulated alternative splicing of a large number of genes enriched in cell death and apoptotic process. Meanwhile, some genes and alternative splicing related to skeletal development were enriched and regulated by FLNB. Quantitative RT-PCR confirmed the FLNB-regulated transcription and alternative splicing. This study provides the first transcriptome-wide analysis of FLNB. Our findings indicated that FLNB may play an important regulatory role in cancer cell apoptosis via the regulation of alternative splicing and potentially transcription, which greatly expands the current understanding of the mechanisms of FLNB mediated gene regulation. Overall design: transcrptional analysis of FLNB knockdown and control in Hela cells
Project description:BACKGROUND:Aberrant spliced isoforms are specifically associated with cancer progression and metastasis. The cytoplasmic adaptor CRKL (v-crk avian sarcoma virus CT10 oncogene homolog-like) is a CRK like proto-oncogene, which encodes a SH2 and SH3 (src homology) domain-containing adaptor protein. CRKL is tightly linked to leukemia via its binding partners BCR-ABL and TEL-ABL, upregulated in multiple types of human cancers, and induce cancer cell proliferation and invasion. However, it remains unclear whether signaling adaptors such as CRKL could regulate alternative splicing. METHODS:We analyzed the expression level of CRKL in 305 cervical cancer tissue samples available in TCGA database, and then selected two groups of cancer samples with CRKL differentially expressed to analyzed potential CRKL-regulated alternative splicing events (ASEs). CRKL was knocked down by shRNA to further study CRKL-regulated alternative splicing and the activity of SR protein kinases in HeLa cells using RNA-Seq and Western blot techniques. We validated 43 CRKL-regulated ASEs detected by RNA-seq in HeLa cells, using RT-qPCR analysis of HeLa cell samples and using RNA-seq data of the two group of clinical cervical samples. RESULTS:The expression of CRKL was mostly up-regulated in stage I cervical cancer samples. Knock-down of CRKL led to a reduced cell proliferation. CRKL-regulated alternative splicing of a large number of genes were enriched in cancer-related functional pathways, among which DNA repair and G2/M mitotic cell cycle, GnRH signaling were shared among the top 10 enriched GO terms and KEGG pathways by results from clinical samples and HeLa cell model. We showed that CRKL-regulated ASEs revealed by computational analysis using ABLas software in HeLa cell were highly validated by RT-qPCR, and also validated by cervical cancer clinical samples. CONCLUSIONS:This is the first report of CRKL-regulation of the alternative splicing of a number of genes critical in tumorigenesis and cancer progression, which is consistent with CRKL reported role as a signaling adaptor and a kinase. Our results underline that the signaling adaptor CRKL might integrate the external and intrinsic cellular signals and coordinate the dynamic activation of cellular signaling pathways including alternative splicing regulation.
Project description:The Sendai virus strain Tianjin is a novel genotype of the Sendai virus. In previous studies, ultraviolet-inactivated Sendai virus strain Tianjin (UV-Tianjin) demonstrated antitumor effects on human breast cancer cells. The aim of the present study was to investigate the in vitro antitumor effects of UV-Tianjin on the human cervical carcinoma HeLa, human small cell lung cancer NCI-H446 and human hepatocellular carcinoma Hep 3B cell lines, and the possible underlying mechanisms of these antitumor effects. A 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay revealed that UV-Tianjin treatment inhibited the proliferation of HeLa, NCI-H446 and Hep 3B cells in a dose- and time-dependent manner. Hoechst and Annexin V-fluorescein isothiocyanate/propidium iodide double staining indicated that UV-Tianjin induced dose-dependent apoptosis in all three cell lines with the most significant effect observed in the HeLa cell line. In the HeLa cell line, UV-Tianjin-induced apoptosis was further confirmed by the disruption of the mitochondria membrane potential and the activation of caspases, as demonstrated by fluorescent cationic dye and colorimetric assays, respectively. In addition, western blot analysis revealed that UV-Tianjin treatment resulted in significant upregulation of cytochrome c, apoptosis protease activating factor-1, Fas, Fas ligand and Fas-associated protein with death domain, and activated caspase-9, -8 and -3 in HeLa cells. Based on these results, it is hypothesized that UV-Tianjin exhibits anticancer activity in HeLa, NCI-H446 and Hep 3B cell lines via the induction of apoptosis. In conclusion, the results of the present study indicate that in the HeLa cell line, intrinsic and extrinsic apoptotic pathways may be involved in UV-Tianjin-induced apoptosis.