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Background: The lncRNA growth arrest-specific 5 (GAS5) is involved in regulating breast cancer progression. In this study, we aimed to elucidate the function and mechanism of GAS5 in breast cancer. Methods: The expressions of GAS5, fat mass and obesity-associated protein (FTO), insulin-like growth factor 2 mRNA-binding protein 2 (IGF2BP2), and Quaking (QKI) were assessed by quantitative reverse transcription-polymerase chain reaction (qRT-PCR) and western blot. The m6A modification level of GAS5 was detected using m6A immunoprecipitation assay (MeRIP). The interaction between IGF2BP2 and GAS5 or QKI was detected using RNA immunoprecipitation assay (RIP) and dual luciferase reporter assay. Cell proliferation was measured using the Cell Counting Kit-8 (CCK-8) assay. The biological functions of the FTO/GAS5/IGF2BP2/QKI axis was assessed using the tumor xenograft assay. Results: LncRNA GAS5 expression decreased in breast cancer and was regulated by FTO-mediated m6A modification in an IGF2BP2-dependent manner, resulting in decreased GAS5 stability and expression. GAS5 recruited IGF2BP2 to target QKI and upregulated QKI expression in breast cancer cells. GAS5 suppressed breast cancer growth via IGF2BP2/QKI, and this inhibitory effect was modulated by FTO both in vitro and in vivo. Conclusions: GAS5 regulated by FTO-mediated m6A modification represses the growth of breast cancer via the IGF2BP2/QKI pathway, suggesting that the FTO/GAS5/IGF2BP2/QKI pathway can be a potential target for breast cancer treatment. [ABSTRACT FROM AUTHOR]

Cervical cancer is the fourth most common female malignancy worldwide and microRNA (miR)-574-5p is a candidate oncogene in multiple cancers. The present study aimed to investigate the role and mechanism of miR-574-5p in cervical cancer. miR-574-5p inhibitors or mimics were transfected into cervical cancer cells to study the function of miR-574-5p. The effects of miR-574-5p on cell growth, invasion, and chemosensitivity were evaluated using CCK8, flow cytometry, transwell, immunofluorescence, and Western blotting analysis. Further depletion or forced expression of QKI was performed to explore the regulatory mechanism of miR-574-5p in cervical cancer. Up-regulation of miR-547-5p and down-regulation of QKI were observed in 30 cervical cancer tissues versus 30 adjacent normal tissues. Silencing of miR-574-5p increased apoptosis, inhibited proliferation, cell cycle progression, and cell invasiveness, as well as enhanced chemosensitivity towards cisplatin and doxorubicin in cervical cancer cells. Overexpression of miR-574-5p exerted promoting effect on cancer progression and metastasis. Knockdown of miR-574-5p induced an up-regulation of E-cadherin and down-regulation of cyclinD1, N-cadherin, matrix metallopeptidase 9 (MMP-9), and β-catenin in cervical cancer cells Moreover, QKI was verified as a target of miR-574-5p and involved in regulation of miR-574-5p-induced cervical cancer cell progression and metastasis. miR-574-5p functions to be oncogenic in cervical cancer, and its inhibition suppresses cervical cancer progression and metastasis as well as enhances chemosensitivity by targeting QKI. Therefore, miR-574-5p is suggested as a potential therapeutic target for cervical cancer treatment. [ABSTRACT FROM AUTHOR]

Purpose: Glioblastoma (GBM) stem cells (GSCs) have been found to be the main cause of malignant GBM progression. It has also been found that Quaking homolog (QKI) plays a predominant role in driving GBM development. Here, we aimed to asses the role of QKI in maintaining GSC stemness and inducing the invasiveness of GBM cells. Methods: Public databases were used to assess the expression of QKI and its correlation with stemness markers in primary GBMs. The CRISPR-Cas9 technology was used to generate QKI knockout GBM cells, and RNA immunoprecipitation was used to assess QKI-GLI1 protein-mRNA interactions. In addition, in vitro and in vivo GBM cell proliferation, migration, xenografting and neurosphere formation assays were performed. Results: Using public GBM databases, QKI was identified as a potential GSC regulator. We found that QKI could inhibit stem-like cell (SLC) stemness and prolong the survival of xenografted mice. Mechanistically, we found that QKI knockout increased the GLI Family Zinc Finger 1 (GLI1) mRNA level, which is essential for maintaining the self-renewal ability of GSCs. In addition, we found that QKI knockout activated the Hedgehog signaling pathway via Tra-2 and GLI response element (TGE)-specific GLI1 mRNA disruption. Conclusion: Our data indicate that upregulation of GLI1 induced by QKI deficiency maintains GSC stemness and enhances the invasiveness of GBM cells, thereby hinting at new options for the treatment of GBM. [ABSTRACT FROM AUTHOR]

The RNA binding protein quaking ( QKI), a key member of the STAR family, as an upstream gene could involve in much process including cell proliferation, apoptosis, differentiation and so on. However, the roles of QKI in germ cell, especially in swine testis (ST) cells, was not clear currently. And apoptosis plays important roles in the growth and development. The purpose of the present study was to clarify the relationship between QKI and apoptosis in ST cells. Firstly, our results showed that pEF1α-QKI and shQKI3 have clear effects on expression levels of QKI. Secondly, we established that QKI directly binds to WT1 3′UTR by binding with QRE-1 (2046-2052 bp, ACTAAC) only. Furthermore, QKI overexpression significantly increased the expression levels of WT1 and Bcl-2. QKI also has the effect on delaying the degradation of WT1 mRNA. In addition, we verified that QKI had a significantly suppressed apoptosis in ST cells. Finally, pBI-WT1 could make up for shQKI3-induced decrease in WT1, Bcl-2 mRNA levels and suppress apoptosis in ST cells. The results demonstrated that QKI was an important regulatory factor that affects apoptosis by targeting WT1 gene. [ABSTRACT FROM AUTHOR]

In this study, we tested the hypothesis that extracellular vesicles (EVs)-mediated transfer of miR-208a/b can exacerbate apoptosis of cardiomyocytes (CMs) induced by hypoxia/reoxygenation (H/R) injury by reducing the expression of the RNA-binding protein Quaking (QKI). EVs were isolated from culture medium of hypoxic H9c2 cells (EVs-H). In in vitro H9c2 cell model, the EVs-H could be taken up by normoxic CMs and exacerbated cell apoptosis induced by H/R injury. In addition, miR-208a and miR-208b were enriched in EVs-H. Suppression of miR-208a and miR-208b loading significantly suppressed the detrimental effect of EVs-H on H/R injury in H9c2 cells. Inhibition of endogenous miR-208a and miR-208b restored QKI5 and QKI6 after H/R treatment. Dual-luciferase assay confirmed direct bindings between miR-208a/b and QKI 3′UTR. Functionally, QKI5 overexpression significantly suppressed H/R-induced CM apoptosis and suppressed the enhancing effect of EVs-H on CM apoptosis. Therefore, we infer that EVs-mediated transfer of miR-208a/b can exaggerate H/R injury in CMs by reducing QKI expression. This represents a previously unrecognized pathway of H/R injury in CMs. [ABSTRACT FROM AUTHOR]

RNA-binding protein QKI, a member of the Signal Transduction and Activation of RNA family, is found to be essential in the blood vessel development and postnatal myelination in central nervous system (Woo et al., Oncogene 28:1176-1186, ; Lu et al., Nucleic Acids Res 31(15):4616-4624, ; Bohnsack et al., Genesis 44(2):93-104, ). However, its wide expression pattern suggests other fundamental roles in vivo (Kondo et al., Mamm Genome 10(7):662-669, ). To facilitate the understanding of QKI function in various systems, we prepared the polyclonal and monoclonal antibodies against QKI. To obtain the antigen, recombinant His-tagged QKI was expressed in Escherichia coli and highly purified by Ni-chelated column combined with hydrophobic and ion exchange methods. Following three types of immunizations with different adjuvants, including Freund's, PAGE gel, and nitrocellulose membrane, only the antiserum produced with Freund's adjuvant is effective for Western blot detection. Several McAb clones are able to recognize both endogenous and over-expressed QKI with high affinity in Western blot and immunofluorescence. The specificity of Ab was validated as weakening, and no specific signals were observed in cells with QKI knocking down. Immunohistochemistry analysis further showed positive staining of QKI in kidney where QKI mRNA was abundantly expressed, ensuring the wide applications of the QKI Abs in the ongoing mechanistic studies. [ABSTRACT FROM AUTHOR]