RNA-binding protein CELF1 promotes tumor growth and alters gene expression in oral squamous cell carcinoma

Loss of CELF2 promotes skin tumorigenesis and increases drug resistance

BACKGROUND

CELF2 belongs to the CELF RNA-binding protein family and exhibits antitumor activity in various tumor models. Analysis of the pan-cancer TCGA database reveals that CELF2 expression strongly correlates with favorable prognosis among cancer patients. The function of CELF2 in nonmelanoma skin cancer has not been studied.

METHODS

We used shRNA-mediated knockdown (KD) of CELF2 expression in human squamous cell carcinoma (SCC) cells to investigate how CELF2 impacted SCC cell proliferation, survival, and xenograft tumor growth. We determined CELF2 expression in human SCC tissues and adjacent normal skin using immunofluorescence staining. Additionally, we investigated the changes in CELF2 and its target gene expression during UV-induced and chemical-induced skin tumorigenesis by western blotting.

RESULTS

CELF2 KD significantly increased SCC cell proliferation, colony growth, and SCC xenograft tumor growth in immunodeficient mice. CELF2 KD in SCC cells led to activation of KRT80 and GDF15, which can potentially promote cell proliferation and tumor growth. While control SCC cells were sensitive to anticancer drugs such as doxorubicin, SCC cells with CELF2 KD became resistant to drug-induced tumor growth retardation. Finally, we found CELF2 expression diminished during both UV- and chemical-induced skin tumorigenesis in mice, consistent with reduced CELF2 expression in human SCC tumors compared to adjacent normal skin.

CONCLUSION

This study shows for the first time that CELF2 loss occurs during skin tumorigenesis and increases drug resistance in SCC cells, highlighting the possibility of targeting CELF2-regulated pathways in skin cancer prevention and therapies.

Curriculum vitae of CUG binding protein 1 (CELF1) in homeostasis and diseases: a systematic review

RNA-binding proteins (RBPs) are kinds of proteins with either singular or multiple RNA-binding domains (RBDs), and they can assembly into ribonucleic acid-protein complexes, which mediate transportation, editing, splicing, stabilization, translational efficiency, or epigenetic modifications of their binding RNA partners, and thereby modulate various physiological and pathological processes. CUG-BP, Elav-like family 1 (CELF1) is a member of the CELF family of RBPs with high affinity to the GU-rich elements in mRNA, and thus exerting control over critical processes including mRNA splicing, translation, and decay. Mounting studies support that CELF1 is correlated with occurrence, genesis and development and represents a potential therapeutical target for these malignant diseases. Herein, we present the structure and function of CELF1, outline its role and regulatory mechanisms in varieties of homeostasis and diseases, summarize the identified CELF1 regulators and their structure-activity relationships, and prospect the current challenges and their solutions during studies on CELF1 functions and corresponding drug discovery, which will facilitate the establishment of a targeted regulatory network for CELF1 in diseases and advance CELF1 as a potential drug target for disease therapy.

High-Throughput Transcriptomics of Celf1 Conditional Knockout Lens Identifies Downstream Networks Linked to Cataract Pathology

Defects in the development of the ocular lens can cause congenital cataracts. To understand the various etiologies of congenital cataracts, it is important to characterize the genes linked to this developmental defect and to define their downstream pathways that are relevant to lens biology and pathology. Deficiency or alteration of several RNA-binding proteins, including the conserved RBP Celf1 (CUGBP Elav-like family member 1), has been described to cause lens defects and early onset cataracts in animal models and/or humans. Celf1 is involved in various aspects of post-transcriptional gene expression control, including regulation of mRNA stability/decay, alternative splicing and translation. Celf1 germline knockout mice and lens conditional knockout (Celf1cKO) mice develop fully penetrant cataracts in early postnatal stages. To define the genome-level changes in RNA transcripts that result from Celf1 deficiency, we performed high-throughput RNA-sequencing of Celf1cKO mouse lenses at postnatal day (P) 0. Celf1cKO lenses exhibit 987 differentially expressed genes (DEGs) at cut-offs of >1.0 log2 counts per million (CPM), ≥±0.58 log2 fold-change and <0.05 false discovery rate (FDR). Of these, 327 RNAs were reduced while 660 were elevated in Celf1cKO lenses. The DEGs were subjected to various downstream analyses including iSyTE lens enriched-expression, presence in Cat-map, and gene ontology (GO) and representation of regulatory pathways. Further, a comparative analysis was done with previously generated microarray datasets on Celf1cKO lenses P0 and P6. Together, these analyses validated and prioritized several key genes mis-expressed in Celf1cKO lenses that are relevant to lens biology, including known cataract-linked genes (e.g., Cryab, Cryba2, Cryba4, Crybb1, Crybb2, Cryga, Crygb, Crygc, Crygd, Cryge, Crygf, Dnase2b, Bfsp1, Gja3, Pxdn, Sparc, Tdrd7, etc.) as well as novel candidates (e.g., Ell2 and Prdm16). Together, these data have defined the alterations in lens transcriptome caused by Celf1 deficiency, in turn uncovering downstream genes and pathways (e.g., structural constituents of eye lenses, lens fiber cell differentiation, etc.) associated with lens development and early-onset cataracts.

Cooperation and competition by RNA-binding proteins in cancer

Post-transcriptional regulation of gene expression plays a major role in determining the cellular proteome in health and disease. Post-transcriptional control mechanisms are disrupted in many cancers, contributing to multiple processes of tumorigenesis. RNA-binding proteins (RBPs), the main post-transcriptional regulators, often show altered expression and activity in cancer cells. Dysregulation of RBPs contributes to many cancer phenotypes, functioning in complex regulatory networks with other cellular players such as non-coding RNAs, signaling mediators and transcription factors to alter the expression of oncogenes and tumor suppressor genes. RBPs often function combinatorially, based on their binding to target sequences/structures on shared mRNA targets, to regulate the expression of cancer-related genes. This gives rise to cooperativity and competition between RBPs in mRNA binding and resultant functional outcomes in post-transcriptional processes such as mRNA splicing, stability, export and translation. Cooperation and competition is also observed in the case of interaction of RBPs and microRNAs with mRNA targets. RNA structural change is a common mechanism mediating the cooperative/competitive interplay between RBPs and between RBPs and microRNAs. RNA modifications, leading to changes in RNA structure, add a new dimension to cooperative/competitive binding of RBPs to mRNAs, further expanding the RBP regulatory landscape. Therefore, cooperative/competitive interplay between RBPs is a major determinant of the RBP interactome and post-transcriptional regulation of gene expression in cancer cells.

CUGBP1, a crucial factor for heart regeneration in mice

The mammalian heart is capable of achieving perfect regeneration following cardiac injury through sustained cardiomyocyte proliferation during the early period after birth. However, this regenerative capacity is lost by postnatal day 7 and throughout adulthood. CUGBP1 is critical for normal cardiac development but its role in heart regeneration remains unclear. Cardiac CUGBP1 levels are high in the early postnatal period and soon downregulate to adult levels within 1 week following birth in mice. The simultaneously diminished regenerative capacity and CUGBP1 levels by postnatal day lead us to hypothesize that CUGBP1 may be beneficial in heart regeneration. In this study, the function of CUGBP1 in heart regeneration was tested by a heart apex resection mouse model. We demonstrate that cardiac inactivation of CUGBP1 impairs neonatal heart regeneration at P1, in turn, replenishment of CUGBP1 levels prolong regenerative potential at P8 and P14. Furthermore, our results imply that the Wnt/β-catenin signaling and GATA4 involve in the CUGBP1 modulated neonatal heart regeneration. Altogether, our findings support CUGBP1 as a key factor promoting post-injury heart regeneration and provide a potential therapeutic method for heart disease.

Identification of Novel Lung Cancer Driver Genes Connecting Different Omics Levels With a Heat Diffusion Algorithm

Cancer driver gene is a type of gene with abnormal alterations that initiate or promote tumorigenesis. Driver genes can be used to reveal the fundamental pathological mechanisms of tumorigenesis. These genes may have pathological changes at different omics levels. Thus, identifying cancer driver genes involving two or more omics levels is essential. In this study, a computational investigation was conducted on lung cancer driver genes. Four omics levels, namely, epigenomics, genomics, transcriptomics, and post-transcriptomics, were involved. From the driver genes at each level, the Laplacian heat diffusion algorithm was executed on a protein–protein interaction network for discovering latent driver genes at this level. A following screen procedure was performed to extract essential driver genes, which contained three tests: permutation, association, and function tests, which can exclude false-positive genes and screen essential ones. Finally, the intersection operation was performed to obtain novel driver genes involving two omic levels. The analyses on obtained genes indicated that they were associated with fundamental pathological mechanisms of lung cancer at two corresponding omics levels.

Circular RNA CELF1 drives immunosuppression and anti-PD1 therapy resistance in non-small cell lung cancer via the miR-491-5p/EGFR axis

Aim: To explore the immunoregulatory effects of circ_CELF1 in non-small cell lung cancer (NSCLC).

Methods: The mRNA level of circ_CELF1 in primary tissue samples was analyzed by qRT-PCR. The assays of CCK-8, colony formation, wound healing as well as Transwell were employed for measurement of cancer cell malignant transformation. The murine subcutaneous tumor model was used to assess the tumorigenesis of NSCLC in vivo. The assays of circRNA precipitation, RNA immunoprecipitation, and luciferase reporter were performed to study the relationship between circ_CELF1, miR-491-5p, and EGFR.

Results: circ_CELF1 is upregulated in primary cancer tissues from patients with NSCLC, and a high level of circ_CELF1, is associated with malignant characteristics and poor outcomes of patients with NSCLC. Enforced expression of circ_CELF1 exacerbated the malignant transformation of NSCLC cells. Mechanistically, through directly interacting with miR-491-5p, circ_CELF1 acted as a miRNA sponge that increased the expression of the miR-491-5p target gene EGFR, eventually promoting the progression of NSCLC and increasing cancer resistance to immunotherapy.

Conclusion: Our data demonstrate that upregulation of circ_CELF1 elicits both oncogenic and immunoregulatory effects on the development of NSCLC. We believe that circ_CELF1 can act as a potential therapeutic target for the treatment of NSCLC.

CELF Family Proteins in Cancer: Highlights on the RNA-Binding Protein/Noncoding RNA Regulatory Axis

Post-transcriptional modifications to coding and non-coding RNAs are unquestionably a pivotal way in which human mRNA and protein diversity can influence the different phases of a transcript's life cycle. CELF (CUGBP Elav-like family) proteins are RBPs (RNA-binding proteins) with pleiotropic capabilities in RNA processing. Their responsibilities extend from alternative splicing and transcript editing in the nucleus to mRNA stability, and translation into the cytoplasm. In this way, CELF family members have been connected to global alterations in cancer proliferation and invasion, leading to their identification as potential tumor suppressors or even oncogenes. Notably, genetic variants, alternative splicing, phosphorylation, acetylation, subcellular distribution, competition with other RBPs, and ultimately lncRNAs, miRNAs, and circRNAs all impact CELF regulation. Discoveries have emerged about the control of CELF functions, particularly via noncoding RNAs, and CELF proteins have been identified as competing, antagonizing, and regulating agents of noncoding RNA biogenesis. On the other hand, CELFs are an intriguing example through which to broaden our understanding of the RBP/noncoding RNA regulatory axis. Balancing these complex pathways in cancer is undeniably pivotal and deserves further research. This review outlines some mechanisms of CELF protein regulation and their functional consequences in cancer physiology.

Alternative splicing: An important regulatory mechanism in colorectal carcinoma

Alternative splicing (AS) is a process that produces various mRNA splicing isoforms via different splicing patterns of mRNA precursors (pre-mRNAs). AS is the primary mechanism for increasing the types and quantities of proteins to improve biodiversity and influence multiple biological processes, including chromatin modification, signal transduction, and protein expression. It has been reported that AS is involved in the tumorigenesis and development of colorectal carcinoma (CRC). In this review, we delineate the concept, types, regulatory processes, and technical advances of AS and focus on the role of AS in CRC initiation, progression, treatment, and prognosis. This summary of the current knowledge about AS will contribute to our understanding of CRC initiation and development. This study will help in the discovery of novel biomarkers and therapeutic targets for CRC prognosis and treatment.

miR-322/miR-503 clusters regulate defective myoblast differentiation in myotonic dystrophy RNA-toxic by targeting Celf1

Myotonic dystrophy (DM) is a genetic disorder featured by muscular dystrophy. It is caused by CUG expansion in the myotonic dystrophy protein kinase gene that leads to aberrant signaling and impaired myocyte differentiation. Many studies have shown that microRNAs are involved in the differentiation process of myoblasts. The purpose of this study was to investigate how the miR-322/miR-503 cluster regulates intracellular signaling to affect cell differentiation. The cell model of DM1 was employed by expressing GFP-CUG200 or CUGBP Elav-like family member 1 (Celf1) in myoblasts. Immunostaining of MF-20 was performed to examine myocyte differentiation. qRT-PCR and western blot were used to determine the levels of Celf1, MyoD, MyoG, Mef2c, miR-322/miR-503, and mitogen-activated protein kinase/extracellular signal-regulated kinase (MEK/ERK) signaling. Dual luciferase assay was performed to validate the interaction between miR-322/miR-503 and Celf1. CUG expansion in myoblasts impaired the cell differentiation, increased the Celf1 level, but it decreased the miR-322/miR-503 levels. miR-322/miR-503 mimics restored the impaired differentiation caused by CUG expansion, while miR-322/miR-503 inhibitors further suppressed. miR-322/miR-503 directly targeted Celf1 and negatively regulated its expression. Knockdown of Celf1 promoted myocyte differentiation. Further, miR-322/miR-503 mimics rescued the impaired differentiation of myocytes caused by CUG expansion or Celf1 overexpression through suppressing of MEK/ERK signaling. miR-322/miR-503 cluster recover the defective myocyte differentiation caused by RNA-toxic via targeting Celf1. Restoring miR-322/miR-503 levels could be an avenue for DM1 therapy.

RNA-binding protein CELF1 enhances cell migration, invasion, and chemoresistance by targeting ETS2 in colorectal cancer

Colorectal cancer (CRC) is often diagnosed at later stages after it has metastasized to other organs. The development of chemoresistance also contributes to a poor prognosis. Therefore, an increased understanding of the metastatic properties of CRC and chemoresistance could improve patient survival. CUGBP elav-like family member 1 (CELF1) is an RNA-binding protein, which is overexpressed in many human malignant tumors. However, the influence of CELF1 in CRC is unclear. V-ets erythroblastosis virus E26 oncogene homologue 2 (ETS2) is an evolutionarily conserved proto-oncogene known to be overexpressed in a variety of human cancers including CRC. In thespresent tudy, we investigated the association between CELF1 and ETS2 in CRC tumorigenesis and oxaliplatin (L-OHP) resistance. We found a positive correlation between the elevated expression of CELF1 and ETS2 in human CRC tissues. Overexpression of CELF1 increased CRC cell proliferation, migration, and invasion in vitro and in a xenograft tumor growth model in vivo, and induced resistance to L-OHP. In contrast, CELF1 knockdown improved the response of CRC cells to L-OHP. Overexpression of ETS2 increased the malignant behavior of CRC cells (growth, migration, and invasion) and L-OHP resistance in vitro. Moreover, L-OHP resistance induced by CELF1 overexpression was reversed by ETS2 knockdown. The results of luciferase reporter and ribonucleoprotein immunoprecipitation assays indicated that CELF1 up-regulates ETS2 by binding to its 3'-UTR. Taken together, our findings have identified that CELF1 regulates ETS2 in a mechanism that results in CRC tumorigenesis and L-OHP resistance, and CELF1 may be a promising target for overcoming chemoresistance in CRC.

Proteomic and Transcriptomic Analysis Identify Spliceosome as a Significant Component of the Molecular Machinery in the Pituitary Tumors Derived from POU1F1- and NR5A1-Cell Lineages

Background: Pituitary adenomas (PA) are the second most common tumor in the central nervous system and have low counts of mutated genes. Splicing occurs in 95% of the coding RNA. There is scarce information about the spliceosome and mRNA-isoforms in PA, and therefore we carried out proteomic and transcriptomic analysis to identify spliceosome components and mRNA isoforms in PA. Methods: Proteomic profile analysis was carried out by nano-HPLC and mass spectrometry with a quadrupole time-of-flight mass spectrometer. The mRNA isoforms and transcriptomic profiles were carried out by microarray technology. With proteins and mRNA information we carried out Gene Ontology and exon level analysis to identify splicing-related events. Results: Approximately 2000 proteins were identified in pituitary tumors. Spliceosome proteins such as SRSF1, U2AF1 and RBM42 among others were found in PA. These results were validated at mRNA level, which showed up-regulation of spliceosome genes in PA. Spliceosome-related genes segregate and categorize PA tumor subtypes. The PA showed alterations in CDK18 and THY1 mRNA isoforms which could be tumor specific. Conclusions: Spliceosome components are significant constituents of the PA molecular machinery and could be used as molecular markers and therapeutic targets. Splicing-related genes and mRNA-isoforms profiles characterize tumor subtypes.

CELF6 modulates triple-negative breast cancer progression by regulating the stability of FBP1 mRNA

BACKGROUND

Triple-negative breast cancer (TNBC) remains a great challenge in clinical treatment due to a shortage of effective therapeutic targets and acquired chemoresistance. Here, we identified the role of an RNA-binding protein, CUG-BP Elav-like family member 6 (CELF6), in the TNBC development and paclitaxel (PTX) chemoresistance.

METHODS

Stable CELF6-overexpressing cell lines were established in BT549 and MDA-MB-231 cells. Cell proliferation was determined using cell counting, two-dimensional colony formation, and MTT assay. Meanwhile, cell migration and cell invasion were detected by Transwell assay. Furthermore, the downstream target gene of CELF6 was identified and the direct interaction was further determined by luciferase reporter assay, immunoprecipitation, and RNA pull-down. Additionally, the PTX resistant cell line was established to determine the role of CELF6 in PTX resistance.

RESULTS

CELF6 overexpression suppressed cell proliferation, cell migration, and cell invasion. Mechanistically, Fructose-Bisphosphatase 1 (FBP1) was identified as the target gene of CELF6 and stabilized by CELF6 via binding 3'UTR. CELF6 overexpression mediated inhibition in TNBC development was dependent on FBP1. Moreover, CELF6 overexpression increased the sensitivity to PTX treatment.

CONCLUSION

CELF6 functions as a tumor suppressor by upregulating FBP 1 expression via stabilizing its mRNA, and thereby inhibits TNBC progression.

MiR-330-3p functions as a tumor suppressor that regulates glioma cell proliferation and migration by targeting CELF1

INTRODUCTION

Glioma is a common type of neoplasm that occurs in the central nervous system. miRNAs have been demonstrated to act as critical regulators of carcinogenesis and tumor progression in multiple cancers, but the molecular mechanism of miR-330-3p in glioma remained unclear. The purpose of the study was to explore the role of miR-330-3p in glioma cell reproduction and migration.

MATERIAL AND METHODS

The expression levels of miR-330-3p and CELF1 in 27 glioma tissue specimens and human glioma cell lines were examined by qRT-PCR and western blot. The TargetScan database was used to predict the relationship between miR-330-3p and CELF1. Then the target relationship was verified using dual-luciferase reporter assay. The effects of miR-330-3p/CELF1 on glioma cell proliferation were evaluated by MTT and colony formation assay. Wound healing assay was employed to measure the migration ability of glioma cells.

RESULTS

MiR-330-3p was found lowly expressed in glioma tissues and cells compared with adjacent tissues and normal astrocytes, while CELF1 expression was relatively high in the glioma tissues and cells. Dual-luciferase reporter assay confirmed that miR-330-3p could directly target CELF1. Furthermore, miR-330-3p could down-regulate the expression of CELF1, therefore suppressing glioma cell reproduction and migration.

CONCLUSIONS

MiR-330-3p inhibited the propagation and migration of glioma cells by repressing CELF1 expression.

A Computational Analysis of Alternative Splicing across Mammalian Tissues Reveals Circadian and Ultradian Rhythms in Splicing Events

Mounting evidence points to a role of the circadian clock in the temporal regulation of post-transcriptional processes in mammals, including alternative splicing (AS). In this study, we carried out a computational analysis of circadian and ultradian rhythms on the transcriptome level to characterise the landscape of rhythmic AS events in published datasets covering 76 tissues from mouse and olive baboon. Splicing-related genes with 24-h rhythmic expression patterns showed a bimodal distribution of peak phases across tissues and species, indicating that they might be controlled by the circadian clock. On the output level, we identified putative oscillating AS events in murine microarray data and pairs of differentially rhythmic splice isoforms of the same gene in baboon RNA-seq data that peaked at opposing times of the day and included oncogenes and tumour suppressors. We further explored these findings using a new circadian RNA-seq dataset of human colorectal cancer cell lines. Rhythmic isoform expression patterns differed between the primary tumour and the metastatic cell line and were associated with cancer-related biological processes, indicating a functional role of rhythmic AS that might be implicated in tumour progression. Our data shows that rhythmic AS events are widespread across mammalian tissues and might contribute to a temporal diversification of the proteome.

Events of alternative splicing in head and neck cancer via RNA sequencing - an update

Background

Alternative splicing (AS) is a regulatory mechanism used to create many forms of mature messengers RNAs (mRNAs) from the same gene. Sequencing of RNA (RNA-Seq) is an advanced technology, which has been utilized by different studies to find AS mechanisms in head and neck cancer (HNC). Hitherto, there is no available review that could inform us of the major findings from these studies. Hence, we aim to perform a systematic literature search following PRISMA guidelines to study AS events in HNC identified through RNA-Seq studies.

Results

A total of five records were identified that utilized RNA-Seq data for identifying AS events in HNC. Five software was used in these records to identify AS events. Two genes influenced by AS i.e. MLL3 and RPS9 were found to be common in 4 out of 5 records. Likewise, 38 genes were identified to be similar in at least 3 records.

Conclusions

Alternative splicing in HNC is a multifaceted regulatory mechanism of gene expression. It can be studied via RNA-Seq using different bioinformatics tools. Genes MLL3, as well as RPS9, were repeatedly found to be associated with HNC, however needs further functional validation.

Electronic supplementary material

The online version of this article (10.1186/s12864-019-5794-y) contains supplementary material, which is available to authorized users.

RNA regulons are essential in intestinal homeostasis

Intestinal epithelial cells are among the most rapidly proliferating cell types in the human body. There are several different subtypes of epithelial cells, each with unique functional roles in responding to the ever-changing environment. The epithelium's ability for rapid and customized responses to environmental changes requires multitiered levels of gene regulation. An emerging paradigm in gastrointestinal epithelial cells is the regulation of functionally related mRNA families, or regulons, via RNA-binding proteins (RBPs). RBPs represent a rapid and efficient mechanism to regulate gene expression and cell function. In this review, we will provide an overview of intestinal epithelial RBPs and how they contribute specifically to intestinal epithelial stem cell dynamics. In addition, we will highlight key gaps in knowledge in the global understanding of RBPs in gastrointestinal physiology as an opportunity for future studies.

Metarrestin, a perinucleolar compartment inhibitor, effectively suppresses metastasis

Metastasis remains a leading cause of cancer mortality due to the lack of specific inhibitors against this complex process. To identify compounds selectively targeting the metastatic state, we used the perinucleolar compartment (PNC), a complex nuclear structure associated with metastatic behaviors of cancer cells, as a phenotypic marker for a high-content screen of over 140,000 structurally diverse compounds. Metarrestin, obtained through optimization of a screening hit, disassembles PNCs in multiple cancer cell lines, inhibits invasion in vitro, suppresses metastatic development in three mouse models of human cancer, and extends survival of mice in a metastatic pancreatic cancer xenograft model with no organ toxicity or discernable adverse effects. Metarrestin disrupts the nucleolar structure and inhibits RNA polymerase (Pol) I transcription, at least in part by interacting with the translation elongation factor eEF1A2. Thus, metarrestin represents a potential therapeutic approach for the treatment of metastatic cancer.

LncRNA OIP5-AS1 is overexpressed in undifferentiated oral tumors and integrated analysis identifies as a downstream effector of stemness-associated transcription factors

Long non-coding RNAs (lncRNAs) play an important role in the regulation of key cellular processes in early development and cancer. LncRNA Oip5-as1 facilitates stem cell self-renewal in mouse by sponging mmu-miR-7 and modulating NANOG level, yet its role in cancer is less understood. We analyzed OIP5-AS1 expression in oral tumors and in TCGA datasets. We observed overexpression of OIP5-AS1 in oral tumors (P < 0.001) and in tumors of epithelial origin from TCGA. OIP5-AS1 expression was strongly associated with undifferentiated tumors (P = 0.0038). In silico analysis showed miR-7 binding site is conserved in mouse and human OIP5-AS1. However, human NANOG 3'-UTR lost the binding site for hsa-miR-7a-3. Therefore, we screened for other miRNAs that can be sponged by OIP5-AS1 and identified six potential miRNAs and their downstream target genes. Expression analysis showed downregulation of miRNAs and upregulation of downstream target genes, particularly in undifferentiated tumors with high-level of OIP5-AS1 suggesting OIP5-AS1 could post-transcriptionally modulate the downstream target genes. Further, systematic epigenomic analysis of OIP5-AS1 promoter revealed binding motifs for MYC, NANOG and KLF4 suggesting that OIP5-AS1 could be transactivated by stemness-associated transcription factors in cancer. OIP5-AS1 overexpression in undifferentiated oral tumors may be suggestive of enhanced cancer stemness, and consequently, poor clinical outcome.

RNA Binding Proteins in Intestinal Epithelial Biology and Colorectal Cancer

The intestinal epithelium is highly proliferative and consists of crypt invaginations that house stem cells and villus projections with differentiated cells. There exists a dynamic equilibrium between proliferation, migration, differentiation, and senescence that is regulated by several factors. Among these are RNA binding proteins (RBPs) that bind their targets in a both context dependent and independent manner. RBP-RNA complexes act as rheostats by regulating expression of RNAs both co- and post-transcriptionally. This is important, especially in response to intestinal injury, to fuel regeneration. The manner in which these RBPs function in the intestine and their interactions with other pivotal pathways in colorectal cancer may provide a framework for new insights and potential therapeutic applications.

Systems analysis identifies melanoma-enriched pro-oncogenic networks controlled by the RNA binding protein CELF1

Melanomas are well-known for their altered mRNA expression profiles. Yet, the specific contribution of mRNA binding proteins (mRBPs) to melanoma development remains unclear. Here we identify a cluster of melanoma-enriched genes under the control of CUGBP Elav-like family member 1 (CELF1). CELF1 was discovered with a distinct prognostic value in melanoma after mining the genomic landscape of the 692 known mRBPs across different cancer types. Genome-wide transcriptomic, proteomic, and RNA-immunoprecipitation studies, together with loss-of-function analyses in cell lines, and histopathological evaluation in clinical biopsies, revealed an intricate repertoire of CELF1-RNA interactors with minimal overlap with other malignancies. This systems approach uncovered the oncogene DEK as an unexpected target and downstream effector of CELF1. Importantly, CELF1 and DEK were found to represent early-induced melanoma genes and adverse indicators of overall patient survival. These results underscore novel roles of CELF1 in melanoma, illustrating tumor type-restricted functions of RBPs in cancer.

Inhibition of CUG-binding protein 1 and activation of caspases are critically involved in piperazine derivative BK10007S induced apoptosis in hepatocellular carcinoma cells

Though piperazine derivative BK10007S was known to induce apoptosis in pancreatic cancer xenograft model as a T-type CaV3.1 a1G isoform calcium channel blocker, its underlying antitumor mechanism still remains unclear so far. Thus, in the present study, the antitumor mechanism of BK10007S was elucidated in hepatocellular carcinoma cells (HCCs). Herein, BK10007S showed significant cytotoxicity by 3-[4,5-2-yl]-2,5-diphenyltetra-zolium bromide (MTT) assay and anti-proliferative effects by colony formation assay in HepG2 and SK-Hep1 cells. Also, apoptotic bodies and terminal deoxynucleotidyl transferase (TdT) dUTP Nick End Labeling (TUNEL) positive cells were observed in BK10007S treated HepG2 and SK-Hep1 cells by 4',6-diamidino-2-phenylinodole (DAPI) staining and TUNEL assay, respectively. Consistently, BK10007S increased sub G₁ population in HepG2 and SK-Hep1 cells by cell cycle analysis. Furthermore, Western blotting revealed that BK10007S activated the caspase cascades (caspase 8, 9 and 3), cleaved poly (ADP-ribose) polymerase (PARP), and downregulated the expression of cyclin D1, survivin and for CUG-binding protein 1 (CUGBP1 or CELF1) in HepG2 and SK-Hep1 cells. Conversely, overexpression of CUGBP1 reduced cleavages of PARP and caspase 3, cytotoxicity and subG₁ population in BK10007S treated HepG2 cells. Overall, these findings provide scientific evidences that BK10007S induces apoptosis via inhibition of CUGBP1 and activation of caspases in hepatocellular carcinomas as a potent anticancer candidate.

3q26-29 Amplification in head and neck squamous cell carcinoma: a review of established and prospective oncogenes

Head and neck squamous cell carcinoma (HNSCC) is significantly underrepresented in worldwide cancer research, yet survival rates for the disease have remained static for over 50 years. Distant metastasis is often present at the time of diagnosis, and is the primary cause of death in cancer patients. In the absence of routine effective targeted therapies, the standard of care treatment remains chemoradiation in combination with (often disfiguring) surgery. A defining characteristic of HNSCC is the amplification of a region of chromosome 3 (3q26-29), which is consistently associated with poorer patient outcome. This review provides an overview of the role the 3q26-29 region plays in HNSCC, in terms of both known and as yet undiscovered processes, which may have potential clinical relevance.

Alternative splicing: the pledge, the turn, and the prestige : The key role of alternative splicing in human biological systems

Alternative pre-mRNA splicing is a tightly controlled process conducted by the spliceosome, with the assistance of several regulators, resulting in the expression of different transcript isoforms from the same gene and increasing both transcriptome and proteome complexity. The differences between alternative isoforms may be subtle but enough to change the function or localization of the translated proteins. A fine control of the isoform balance is, therefore, needed throughout developmental stages and adult tissues or physiological conditions and it does not come as a surprise that several diseases are caused by its deregulation. In this review, we aim to bring the splicing machinery on stage and raise the curtain on its mechanisms and regulation throughout several systems and tissues of the human body, from neurodevelopment to the interactions with the human microbiome. We discuss, on one hand, the essential role of alternative splicing in assuring tissue function, diversity, and swiftness of response in these systems or tissues, and on the other hand, what goes wrong when its regulatory mechanisms fail. We also focus on the possibilities that splicing modulation therapies open for the future of personalized medicine, along with the leading techniques in this field. The final act of the spliceosome, however, is yet to be fully revealed, as more knowledge is needed regarding the complex regulatory network that coordinates alternative splicing and how its dysfunction leads to disease.

Neonatal cardiac dysfunction and transcriptome changes caused by the absence of Celf1

The RNA binding protein Celf1 regulates alternative splicing in the nucleus and mRNA stability and translation in the cytoplasm. Celf1 is strongly down-regulated during mouse postnatal heart development. Its re-induction in adults induced severe heart failure and reversion to fetal splicing and gene expression patterns. However, the impact of Celf1 depletion on cardiac transcriptional and posttranscriptional dynamics in neonates has not been addressed. We found that homozygous Celf1 knock-out neonates exhibited cardiac dysfunction not observed in older homozygous animals, although homozygous mice are smaller than wild type littermates throughout development. RNA-sequencing of mRNA from homozygous neonatal hearts identified a network of cell cycle genes significantly up-regulated and down-regulation of ion transport and circadian genes. Cell cycle genes are enriched for Celf1 binding sites supporting a regulatory role in mRNA stability of these transcripts. We also identified a cardiac splicing network coordinated by Celf1 depletion. Target events contain multiple Celf1 binding sites and enrichment in GU-rich motifs. Identification of direct Celf1 targets will advance our knowledge in the mechanisms behind developmental networks regulated by Celf1 and diseases where Celf1 is mis-regulated.

RNA-binding protein CUGBP1 regulates insulin secretion via activation of phosphodiesterase 3B in mice

AIMS/HYPOTHESIS

CUG-binding protein 1 (CUGBP1) is a multifunctional RNA-binding protein that regulates RNA processing at several stages including translation, deadenylation and alternative splicing, as well as RNA stability. Recent studies indicate that CUGBP1 may play a role in metabolic disorders. Our objective was to examine its role in endocrine pancreas function through gain- and loss-of-function experiments and to further decipher the underlying molecular mechanisms.

METHODS

A mouse model in which type 2 diabetes was induced by a high-fat diet (HFD; 60% energy from fat) and mice on a standard chow diet (10% energy from fat) were compared. Pancreas-specific CUGBP1 overexpression and knockdown mice were generated. Different lengths of the phosphodiesterase subtype 3B (PDE3B) 3' untranslated region (UTR) were cloned for luciferase reporter analysis. Purified CUGBP1 protein was used for gel shift experiments.

RESULTS

CUGBP1 is present in rodent islets and in beta cell lines; it is overexpressed in the islets of diabetic mice. Compared with control mice, the plasma insulin level after a glucose load was significantly lower and glucose clearance was greatly delayed in mice with pancreas-specific CUGBP1 overexpression; the opposite results were obtained upon pancreas-specific CUGBP1 knockdown. Glucose- and glucagon-like peptide1 (GLP-1)-stimulated insulin secretion was significantly attenuated in mouse islets upon CUGBP1 overexpression. This was associated with a strong decrease in intracellular cAMP levels, pointing to a potential role for cAMP PDEs. CUGBP1 overexpression had no effect on the mRNA levels of PDE1A, 1C, 2A, 3A, 4A, 4B, 4D, 7A and 8B subtypes, but resulted in increased PDE3B expression. CUGBP1 was found to directly bind to a specific ATTTGTT sequence residing in the 3' UTR of PDE3B and stabilised PDE3B mRNA. In the presence of the PDE3 inhibitor cilostamide, glucose- and GLP-1-stimulated insulin secretion was no longer reduced by CUGBP1 overexpression. Similar to CUGBP1, PDE3B was overexpressed in the islets of diabetic mice.

CONCLUSIONS/INTERPRETATION

We conclude that CUGBP1 is a critical regulator of insulin secretion via activating PDE3B. Repressing this protein might provide a potential strategy for treating type 2 diabetes.

Genes associated with Alzheimer's disease: an overview and current status

Alzheimer's disease (AD) is a progressive, neurodegenerative disease and the most common form of dementia in elderly people. It is an emerging public health problem that poses a huge societal burden. Linkage analysis was the first milestone in unraveling the mutations in APP, PSEN1, and PSEN2 that cause early-onset AD, followed by the discovery of apolipoprotein E-ε4 allele as the only one genetic risk factor for late-onset AD. Genome-wide association studies have revolutionized genetic research and have identified over 20 genetic loci associated with late-onset AD. Recently, next-generation sequencing technologies have enabled the identification of rare disease variants, including unmasking small mutations with intermediate risk of AD in PLD3, TREM2, UNC5C, AKAP9, and ADAM10. This review provides an overview of the genetic basis of AD and the relationship between these risk genes and the neuropathologic features of AD. An understanding of genetic mechanisms underlying AD pathogenesis and the potentially implicated pathways will lead to the development of novel treatment for this devastating disease.