WIG1 is crucial for AGO2-mediated ACOT7 mRNA silencing via miRNA-dependent and -independent mechanisms

ATXN2L primarily interacts with NUFIP2, the absence of ATXN2L results in NUFIP2 depletion, and the ATXN2-polyQ expansion triggers NUFIP2 accumulation

The cytoplasmic Ataxin-2 (ATXN2) protein associates with TDP-43 in stress granules (SG) where RNA quality control occurs. Mutations in this pathway underlie Spinocerebellar Ataxia type 2 (SCA2) and Amyotrophic Lateral Sclerosis. In contrast, Ataxin-2-like (ATXN2L) is predominantly perinuclear, more abundant, and essential for embryonic life. Its sequestration into ATXN2 aggregates may contribute to disease. In this study, we utilized two approaches to clarify the roles of ATXN2L. First, we identified interactors through co-immunoprecipitation in both wild-type and ATXN2L-null murine embryonic fibroblasts. Second, we assessed the proteome profile effects using mass spectrometry in these cells. Additionally, we examined the accumulation of ATXN2L interactors in the SCA2 mouse model, Atxn2-CAG100-KnockIn (KIN). We observed that RNA-binding proteins, including PABPN1, NUFIP2, MCRIP2, RBMS1, LARP1, PTBP1, FMR1, RPS20, FUBP3, MBNL2, ZMAT3, SFPQ, CSDE1, HNRNPK, and HNRNPDL, exhibit a stronger association with ATXN2L compared to established interactors like ATXN2, PABPC1, LSM12, and G3BP2. Additionally, ATXN2L interacted with components of the actin complex, such as SYNE2, LMOD1, ACTA2, FYB, and GOLGA3. We noted that oxidative stress increased HNRNPK but decreased SYNE2 association, which likely reflects the relocalization of SG. Proteome profiling revealed that NUFIP2 and SYNE2 are depleted in ATXN2L-null fibroblasts. Furthermore, NUFIP2 homodimers and SYNE1 accumulate during the ATXN2 aggregation process in KIN 14-month-old spinal cord tissues. The functions of ATXN2L and its interactors are therefore critical in RNA granule trafficking and surveillance, particularly for the maintenance of differentiated neurons.

In Vivo Imaging MicroRNA with Bright Fluorescent RNA Aptamer Through Target-Mediated Entropy-Driven Toehold Exchange

MicroRNAs (miRNAs) play vital roles in biological activities, but their in vivo imaging is still challenging due to the low abundance and the lack of efficient fluorescent tools. RNA aptamers with high affinity and low background emerge for bioimaging yet suffering from low brightness. We introduce a rational design based on target-mediated entropy-driven toehold exchange (EDTE) to induce the release of RNA aptamer and subsequently light up corresponding fluorophore, which achieves selective imaging of miRNAs with good stability in both living cells and tumor-bearing mouse. Through tailoring recognition unit of the EDTE probes, highly sensitive imaging of different miRNAs including miRNA-125b and miRNA-21 is achieved, confirming its universal bioimaging applications. In comparison with the reported "one-to-one" model, the EDTE strategy shows a remarkable 4.6-time improvement in signal/noise ratio for intracellular imaging of the same miRNA. Particularly, it realizes sensitive imaging of miRNA in vivo, providing a promising tool in investigating functions and interactions of disease-associated miRNAs.

Polypyrimidine tract-binding protein 3/insulin-like growth factor 2 mRNA-binding proteins 3/high-mobility group A1 axis promotes renal cancer growth and metastasis

Polypyrimidine tract-binding protein 3 (PTBP3) plays an important role in the post-transcriptional regulation of gene expression, including mRNA splicing, translation, and stability. Increasing evidence has shown that PTBP3 promotes cancer progression in several tumor types. However, the molecular mechanisms of PTBP3 in renal cell carcinoma (RCC) remain unknown. Here, tissue microarrays (TMAs) suggested that PTBP3 expression was increased in human RCC and that high PTBP3 expression was correlated with poor five-year overall survival and disease-free survival. We also showed that PTBP3 binds with HMGA1 mRNA in the 3'UTR region and let-7 miRNAs. PTBP3 interacted with IGF2BP3, and the PTBP3/IGF2BP3 axis prevented let-7 mediated HMGA1 mRNA silencing. PTBP3 promotes renal cancer cell growth and metastasis in vitro and in vivo. Taken together, our findings indicate PTBP3 serves as a regulator of HMGA1 and suggest its potential as a therapeutic agent for RCC.

eIF5B regulates the expression of PD-L1 in prostate cancer cells by interacting with Wig1

BACKGROUND

Eukaryotic translation initiation factors (eIFs) are the key factors to synthesize translation initiation complexes during the synthesis of eukaryotic proteins. Besides, eIFs are especially important in regulating the immune function of tumor cells. However, the effect mechanism of eIFs in prostate cancer remains to be studied, which is precisely the purpose of this study.

METHODS

In this study, three groups of prostate cancer cells were investigated. One group had its eIF5B gene knocked down; another group had its Programmed death 1 (PD-L1) overexpressed; the final group had its Wild-type p53-induced gene 1 (Wig1) overexpressed. Genetic alterations of the cancer cells were performed by plasmid transfection. The expression of PD-L1 mRNA was detected by quantitative real-time PCR (qRT-PCR), and the expressions of PD-L1 and eIF5B proteins were observed by western blot assays. Cell Counting Kit-8 (CCK-8), flow cytometry, Transwell and Transwell martrigel were used to investigated cell proliferation, apoptosis, migration and invasion, respectively. The effect of peripheral blood mononuclear cells (PBMCs) on tumor cells was observed, and the interaction between eIF5B and Wig1 was revealed by co-immunoprecipitation (CoIP) assay. Finally, the effects of interference with eIF5B expression on the growth, morphology, and immunity of the tumor, as well as PD-L1 expression in the tumor, were verified by tumor xenograft assays in vivo.

RESULTS

Compared with normal prostate epithelial cells, prostate cancer cells revealed higher expressions of eIF5B and PD-L1 interference with eIF-5B expression can inhibit the proliferation, migration, invasion and PD-L1 expression of prostate cancer cells. Meanwhile, the cancer cell group with interference with eIF5B expression also demonstrated greater, apoptosis and higher vulnerability to PBMCs. CoIP assays showed that Wig1 could bind to eIF5B in prostate cancer cells, and its overexpression can inhibit the proliferation, migration, invasion and PD-L1 expression of cancer cells while promoting apoptosis. Moreover, interference with eIF5B expression can inhibit tumor growth, destroy tumor morphology, and suppress the proliferation of tumor cells.

CONCLUSION

eIF5B can promote the expression of PD-L1 by interacting with Wig1. Besides, interference with eIF5B expression can inhibit the proliferation, migration, invasion and immunosuppressive response of prostate cancer cells. This study proposes a new target, eIF5B, for immunotherapy of prostate cancer.

RNA-Binding Proteins in Cancer: Functional and Therapeutic Perspectives

Simple Summary

RNA-binding proteins (RBPs) play central roles in regulating posttranscriptional expression of genes. Many of them are known to be deregulated in a wide variety of cancers. Dysregulated RBPs influence the expression levels of target RNAs related to cancer phenotypes, such as proliferation, apoptosis, angiogenesis, senescence, and EMT/invasion/metastasis. Thus, understanding the molecular functions of RBPs and their roles in cancer-related phenotypes can lead to improved therapeutic strategies.

Abstract

RNA-binding proteins (RBPs) crucially regulate gene expression through post-transcriptional regulation, such as by modulating microRNA (miRNA) processing and the alternative splicing, alternative polyadenylation, subcellular localization, stability, and translation of RNAs. More than 1500 RBPs have been identified to date, and many of them are known to be deregulated in cancer. Alterations in the expression and localization of RBPs can influence the expression levels of oncogenes, tumor-suppressor genes, and genome stability-related genes. RBP-mediated gene regulation can lead to diverse cancer-related cellular phenotypes, such as proliferation, apoptosis, angiogenesis, senescence, and epithelial-mesenchymal transition (EMT)/invasion/metastasis. This regulation can also be associated with cancer prognosis. Thus, RBPs can be potential targets for the development of therapeutics for the cancer treatment. In this review, we describe the molecular functions of RBPs, their roles in cancer-related cellular phenotypes, and various approaches that may be used to target RBPs for cancer treatment.

A novel long noncoding RNA Linc-ASEN represses cellular senescence through multileveled reduction of p21 expression

Long noncoding RNAs (lncRNAs) regulating diverse cellular processes implicate in many diseases. However, the function of lncRNAs in cellular senescence remains largely unknown. Here we identify a novel long intergenic noncoding RNA Linc-ASEN expresses in prematurely senescent cells. We find that Linc-ASEN associates with UPF1 by RNA pulldown mass spectrometry analysis, and represses cellular senescence by reducing p21 production transcriptionally and posttranscriptionally. Mechanistically, the Linc-ASEN-UPF1 complex suppressed p21 transcription by recruiting Polycomb Repressive Complex 1 (PRC1) and PRC2 to the p21 locus, and thereby preventing binding of the transcriptional activator p53 on the p21 promoter through histone modification. In addition, the Linc-ASEN-UPF1 complex repressed p21 expression posttranscriptionally by enhancing p21 mRNA decay in association with DCP1A. Accordingly, Linc-ASEN levels were found to correlate inversely with p21 mRNA levels in tumors from patient-derived mouse xenograft, in various human cancer tissues, and in aged mice tissues. Our results reveal that Linc-ASEN prevents cellular senescence by reducing the transcription and stability of p21 mRNA in concert with UPF1, and suggest that Linc-ASEN might be a potential therapeutic target in processes influenced by senescence, including cancer.

AGO2 Mediates MYC mRNA Stability in Hepatocellular Carcinoma

Deregulated RNA-binding proteins (RBP), such as Argonaute 2 (AGO2), mediate tumor-promoting transcriptomic changes during carcinogenesis, including hepatocellular carcinoma (HCC). While AGO2 is well characterized as a member of the RNA-induced silencing complex (RISC), which represses gene expression through miRNAs, its role as a bona fide RBP remains unclear. In this study, we investigated AGO2's role as an RBP that regulates the MYC transcript to promote HCC. Using mRNA and miRNA arrays from patients with HCC, we demonstrate that HCCs with elevated AGO2 levels are more likely to have the mRNA transcriptome deregulated and are associated with poor survival. Moreover, AGO2 overexpression stabilizes the MYC transcript independent of miRNAs. These observations provide a novel mechanism of gene regulation by AGO2 and provide further insights into the potential functions of AGO2 as an RBP in addition to RISC. IMPLICATIONS: Authors demonstrate that the RBP Argonaute 2 stabilizes the MYC transcript to promote HCC.

A potential regulatory network among WDR86-AS1, miR-10b-3p, and LITAF is possibly involved in preeclampsia pathogenesis

Preeclampsia (PE), a pregnancy-specific disorder, is a leading cause of perinatal maternal and fetal mortality and morbidity. Impaired migration and invasion of trophoblastic cells and an imbalanced systemic maternal inflammatory response have been proposed as possible causes of pathogenesis of PE. Comparative analysis of PE-affected placentas and healthy placentas has uncovered differentially expressed long noncoding RNAs, microRNAs, and mRNAs. This study was conducted to investigate the effect of a regulatory network among these RNAs on PE pathogenesis. Long noncoding RNA WDR86-AS1, microRNA miR-10b-3p, and mRNA of protein LITAF were identified by screening of genes in existing databases with aberrant expression in PE-affected placentas and potential mutual interactions as revealed by TargetScan, miRanda, and PicTar analyses. This study identified their expression in PE-affected and healthy placentas by RT-PCR. An in vitro experiment was performed on human trophoblast HTR-8/SVneo cells cultured under normoxic or hypoxic conditions. MiR-10b-3p targets were identified in luciferase reporter assays and RNA pull-down assays. The mouse model of PE was set up using a soluble form of FLT-1 for in vivo testing. Lower levels of miR-10b-3p but higher expression of WDR86-AS1 and LITAF were observed in PE-affected placentas and trophoblast cells under hypoxia. WDR86-AS1 and LITAF mRNA were confirmed as targets of miR-10b-3p. WDR86-AS1 downregulated miR-10b-3p but promoted LITAF expression. Microarray analyses revealed that LITAF controlled the inflammatory responses and migration and proliferation of HTR-8/SVneo cells under hypoxia. Indeed, knockdown of WDR86-AS1 and LITAF or overexpression of miR-10b-3p attenuated the hypoxia-induced inhibition of cellular viability, migration, and invasion. Moreover, miR-10b-3p overexpression attenuated the pathological symptoms caused by soluble FLT-1 in vivo. In summary, the WDR86-AS1/miR-10b-3p/LITAF network is probably involved in PE pathogenesis.

PTBP3 splicing factor promotes hepatocellular carcinoma by destroying the splicing balance of NEAT1 and pre-miR-612

Nuclear-enriched RNA-binding proteins (RBPs) are mainly involved in transcriptional regulation, which is a critical checkpoint to tune gene diversity and expression levels. We analyzed nuclear RBPs in human HCC tissues and matched normal control tissues. Based on the gene expression levels, PTBP3 was identified as top-ranked in the nuclei of HCC cells. HCC cell lines then were transfected with siRNAs or lentiviral vectors. PTBP3 promoted HCC cell proliferation and metastasis both in vitro and in vivo. RNA immunoprecipitation (RIP), fluorescence in situ hybridization (FISH) and qRT-PCR assays verified that PTBP3 protein recruited abundant lnc-NEAT1 splicing variants (NEAT1_1 and NEAT1_2) and pre-miR-612 (precursor of miR-612) in the nucleus. NEAT1_1, NEAT1_2 and miR-612 expression levels were determined by PTBP3. Correlational analyses revealed that PTBP3 was positively correlated with NEAT1, but it was inversely correlated with miR-612 in HCC. The P53/CCND1 and AKT2/EMT pathways were determined by NEAT1 and miR-612 respectively in HCC. The PTBP3^high and NEAT1^high/miR-612^low patients had a shorter overall survival. Therefore, nuclear-enriched RBP, PTBP3, promotes HCC cell malignant growth and metastasis by regulating the balance of splicing variants (NEAT1_1, NEAT1_2 and miR-612) in HCC.