Quaking Expression Research Articles

An ancient competition for the conserved branchpoint sequence influences physiological and evolutionary outcomes in splicing.

Recognition of the intron branchpoint during spliceosome assembly is a multistep process that defines both mRNA structure and amount. A branchpoint sequence motif UACUAAC is variably conserved in eukaryotic genomes, but in some organisms more than one protein can recognize it. Here we show that SF1 and Quaking (QKI) compete for a subset of intron branchpoints with the sequence ACUAA. SF1 activates exon inclusion through this sequence, but QKI represses the inclusion of alternatively spliced exons with this intron branchpoint sequence. Using mutant reporters derived from a natural intron with two branchpoint-like sequences, we find that when either branchpoint sequence is mutated, the other is used as a branchpoint, but when both are present, neither is used due to high affinity binding and strong splicing repression by QKI. QKI occupancy at the dual branchpoint site directly prevents SF1 binding and subsequent recruitment of spliceosome-associated factors. Finally, the ectopic expression of QKI in budding yeast (which lacks QKI) is lethal, due at least in part to widespread splicing repression. In conclusion, QKI can function as a splicing repressor by directly competing with SF1/BBP for a subset of branchpoint sequences that closely mirror its high affinity binding site. This suggests that QKI and degenerate branchpoint sequences may have co-evolved as a means through which specific gene expression patterns could be maintained in QKI-expressing or non-expressing cells in metazoans, plants, and animals.

GAS5 regulated by FTO-mediated m6A modification suppresses cell proliferation via the IGF2BP2/QKI axis in breast cancer

BackgroundThe 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.MethodsThe 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.ResultsLncRNA 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.ConclusionsGAS5 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.

The RNA-binding protein quaking is upregulated in nitrofen-induced congenital diaphragmatic hernia lungs at the end of gestation.

The RNA-binding protein Quaking (QKI) increases during epithelial-to-mesenchymal transition and its expression is controlled by microRNA-200 family members. Here, we aimed to describe the expression of QKI in the developing lungs of control and nitrofen-induced congenital diaphragmatic hernia lungs (CDH). To investigate the expression of QKI, we dissected lungs from control and nitrofen-induced CDH rats on embryonic day 15, 18, 21 (E15, E18, E21). We performed immunofluorescence (IF) and quantitative reverse transcription PCR (RT-qPCR) for QKI expression. Additionally, we assessed Interleukin-6 (IL-6) abundance using IF. On E21, IF showed that the abundance of all three QKI isoforms and IL-6 protein was higher in CDH lungs compared to control lungs (QKI5: p = 0.023, QKI6: p = 0.006, QKI7: p = 0.014, IL-6: p = 0.045, respectively). Furthermore, RT-qPCR data showed increased expression of QKI5, QKI6, and QKI7 mRNA in E21 nitrofen lungs by 1.63 fold (p = 0.001), 1.63 fold (p = 0.010), and 1.48 fold (p = 0.018), respectively. Our data show an increase in the abundance and expression of QKI at the end of gestation in nitrofen-induced CDH lungs. Therefore, a disruption in the regulation of QKI during the late stage of pregnancy could be associated with the pathogenesis of abnormal lung development in CDH.

Clinicopathologic Significance of Quaking Expression in Hepatocellular Carcinoma.

The RNA binding protein quaking (QKI) is associated with the development and progression of tumor suppressors in various cancers. However, the clinical implications of QKI expression have not yet been fully elucidated. In this study, we aimed to investigate the clinicopathological and prognostic significance of QKI expression in hepatocellular carcinoma (HCC). We performed QKI, Zinc finger E-box-binding homeobox 1 (ZEB1), E-cadherin, and glutathione peroxidase 4 (GPX4) immunohistochemical staining on 166 HCC patient tissue samples. X-tile bioinformatics software was used to set the cut-off value for high QKI expression. Correlations between QKI expression and various clinicopathological parameters were assessed. The best cut-off value for high QKI expression was 12.5. High QKI expression was observed in 28 of 166 patients (16.9%) and was an independent prognostic factor for inferior recurrence-free survival (RFS). In addition, high ZEB1 and GPX4 expression correlated with high QKI expression, but not with the loss of E-cadherin expression. High QKI expression was identified in HCCs and associated with poor RFS. QKI might be a prognostic biomarker of HCCs associated with epithelial-to-mesenchymal transition and a potential candidate therapeutic target.

Abstract 1224: Quaking overexpression downregulates epithelial-mesenchymal transition in lung cancer cells

Abstract Background: Lung cancer is the leading cause of cancer death worldwide. Tumor recurrence is the most common cause of treatment failure after surgical resection. Quaking (QKI) is a functional protein that mediate alternative splicing, which belongs to the STAR family of the KH domain, containing RNA binding proteins. QKI regulate various genes via alternative splicing and circRNA formation during epithelial-mesenchymal transition (EMT). QKI takes an important part in tumorigenesis. QKI has been reported to be associated with progression of human cancer. However, several studies have indicated that QKI was associated with repression of EMT. Furthermore, the prognostic value of QKI in lung cancer patients and its regulatory mechanisms in EMT in lung cancer cells remains unknown. Materials and Methods: A total of 79 patients with resected lung adenocarcinoma were included in the study. QKI expression was determined by immunohistochemistry in tumor specimens. The prognostic value of QKI overexpression and its relationship with clinicopathological variables were investigated. QKI knockdown was performed in H1299 and A549 cells. Western blotting analysis was performed to demonstrated QKI, E-cadherin and vimentin expression. Results: QKI overexpression was significantly associated with female gender (P = 0.045). There was no significant association between QKI overexpression and predominant pattern group (lepidic/acinar/papillary vs. micropapillary/solid) (P = 0.180). Univariate analysis indicated that predominant pattern group (lepidic/acinar/papillary vs. micropapillary/solid) (P = 0.006) was a significant prognostic factor for worse recurrence-free survival (RFS). QKI overexpression (P = 0.042) was a significant prognostic factor for better RFS. Increased vimentin expression and decreased E-cadherin expression were identified in H1299 and A549 cells after QKI knockdown. Conclusions: QKI overexpression has the potential to be a significant prognostic factor for better RFS in patients with resected lung adenocarcinoma. Increased vimentin expression and decreased E-cadherin expression were identified in H1299-QKIi cells. QKI may possess the ability to inhibit invasion and migration through repressing EMT. Citation Format: Ying-Shiun Kao, Jung-Jyh Hung. Quaking overexpression downregulates epithelial-mesenchymal transition in lung cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1224.

QKI degradation in macrophage by RNF6 protects mice from MRSA infection via enhancing PI3K p110β dependent autophagy

BackgroundSepsis is a fatal condition commonly caused by Methicillin-resistant Staphylococcus aureus (MRSA) with a high death rate. Macrophages can protect the host from various microbial pathogens by recognizing and eliminating them. Earlier we found that Quaking (QKI), an RNA binding protein (RBP), was involved in differentiation and polarization of macrophages. However, the role of QKI in sepsis caused by pathogenic microbes, specifically MRSA, is unclear. This study aimed to investigate the role of QKI in regulation of host–pathogen interaction in MRSA-induced sepsis and explored the underlying mechanisms.MethodsTransmission electron microscope and immunofluorescence were used to observe the autophagy level in macrophages. Real-time PCR and western blot were used to analyzed the expression of mRNA and protein respectively. The potential protein interaction was analyzed by iTRAQ mass spectrometry and Immunoprecipitation. RNA fluorescence in situ hybridization, dual-luciferase reporter assay and RNA immunoprecipitation were used to explore the mechanism of QKI regulating mRNA of PI3K-p110β.ResultsThe mRNA level of QKI was aberrantly decreased in monocytes and PBMCs of septic patients with the increasing level of plasma procalcitonin (PCT). Then the mice with myeloid specific knockout of QKI was challenged with MRSA or Cecal Ligation and Puncture (CLP). Mice in these two models displayed higher survival rates and lower bacterial loads. Mechanistically, QKI deletion promoted phagocytosis and autophagic degradation of MRSA via activating p110β (a member of Class IA phosphoinositide 3-kinases) mediated autophagic response. QKI expression in macrophages led to the sequestration of p110β in mRNA processing (P) bodies and translational repression. Upon infection, the direct interaction of RNF6, a RING-type E3 ligase, mediated QKI ubiquitination degradation and facilitated PI3K-p110β related autophagic removal of pathogen. The administration of nanoparticles with QKI specific siRNA significantly protected mice from MRSA infection.ConclusionsThis study disclosed the novel function of QKI in the P body mRNA regulation during infection. QKI degradation in macrophage by RNF6 protects mice from MRSA infection via enhancing PI3K-p110β dependent autophagy. It suggested that QKI may serve as a potential theranostic marker in MRSA-induced sepsis.Graphical

EP08.02-093 Loss of Tumor Endothelial QKI Expression Results in Pronounced Reductions in Metastasis and Remodeling of the Tumor Microenvironment

The TME encompasses cross talk between different cells and stromal elements within the tumor. While the interplay between the tumor microenvironment (TME) and metastasis is well established, only a few TME targets have resulted in approved therapeutic agents against highly metastatic lung cancers. Quaking (QKI) is a highly conserved RNA-binding protein that plays critical roles in vascular development during embryogenesis. Previous work in our lab revealed that the miR-200 family regulates tumor angiogenesis by targeting QKI, and loss of QKI resulted in inhibition of sprouting angiogenesis and endothelial proliferation.

Evaluation of miR-429 as a novel serum biomarker for pancreatic ductal adenocarcinoma and analysis its tumor suppressor function and target genes.

Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal types of cancer. Various microRNAs have been identified to play an important role in PDAC. The study aimed to explore the role of miR-429 in PDAC. The expression and prognostic value of miR-429 were first analyzed using The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) databases. Next, miR-429 expression was evaluated in the tissues and serum of 90 patients with PDAC. CCK8, SRB, wound healing and transwell assays were used to determine the effect of miR-429 on the proliferation, invasion, and migration of PDAC cells, respectively. Weighted gene co-expression network analysis (WGCNA), correlation analysis, TargetScan, and miRDB databases were used to screen and identify the target genes of miR-429. The results revealed that the expression of miR-429 was downregulated in PDAC tissues and the serum compared with those in normal tissues and the serum of healthy volunteers, respectively. The decreased expression of miR-429 was significantly associated with shorter overall survival. The overexpression of miR-429 significantly inhibited the proliferation, invasion, and migration of PDAC cells. Potential target genes of miR-429 were identified using WGCNA and bioinformatics analysis, and the results showed that cadherin 11 (CDH11), inositol polyphosphate-4-phosphatase type I (INPP4A), laminin gamma 1 (LAMC1), low density lipoprotein receptor-related protein 1 (LRP1), and quaking (QKI) were potential target genes of miR-429 in PDAC. Lower expression of CDH11 and QKI was associated with a more favorable prognosis in patients with PDAC. The overexpression of miR-429 could inhibit the expression of CDH11 and QKI. A nomogram model, involving miR-429, CDH11, and QKI, was subsequently constructed to determine their ability to accurately predict overall and disease-free survival in patients with PDAC. Taken together, miR-429 is involved in the development and progress of PDAC. MiR-429 could be recommended as a prognostic biomarker and therapeutic indicator in PDAC diagnosis.

Abstract 2270: Hyperlipidemia promotes aggressive variant prostate cancer via RNA-binding protein Quaking

Abstract Introduction: Hyperlipidemia has been associated with increased risk of advanced stage and high Gleason grade prostate cancer (PCa), yet the underlying mechanism is not completely understood. Quaking (QKI) is an RNA-binding protein (RBP) that regulate lipid metabolism. For PCa, QKI overexpression has been associated with increased chance of metastatic recurrence. Method: We performed RNA sequencing of prostate cancer tissues of hyperlipidemia (n = 12) and normolipidemia (n=32). Tissue samples were acquired by MRI-US fusion targeted biopsy. DESeq2 and GSEA was used to identify differently expressed genes and enriched genesets. A web-based RBP motif screening tool TRANSITE was utilized to identify active RBPs in hyperlipidemia-associated PCa. Results: PCa samples of hyperlipidemia patients exhibited poorer histology than normolipidemia PCA. RNA sequencing found that hyperlipidemia-associated PCa is enriched of Myc-regulated genes as well as interferon or innate immunity-associated genes. Interestingly, hyperlipidemia-associated PCa gene expression signature identified PCa samples devoid of common PCa genetic alterations - TMPRSS2-ERG fusion and PTEN deletion/mutation. RBP motif screening found QKI as one of the top enriched RBP in hyperlipidemia-associated PCa transcriptome. In a separate a consecutive radical prostatectomy series (n=190), we found that QKI-high (immunohistochemistry staining score 2-3) tumors had significantly higher serum cholesterol than QKI-low (score 0-1) tumors. Overexpression and knockdown experiments proved that QKI is responsible of rapid cell proliferation and interferon-related inflammatory gene expressions, In silico analysis predicted QKI overexpressing cancer cells are susceptive to stain-mediated ferroptosis-like cell death. Mechanistically, QKI regulates expression of acyl-CoA synthetase long-chain family member 4 (ACSL4), which dictates the sensitivity of QKI overexpressing cells to ferroptosis. Conclusion: Hyperlipidemia was associated with aggressive pathologic characteristics of PCa without TMPRSS2-ERG fusion or PTEN deletion/mutation, and high tissue expression of QKI, an RNA-binding protein. QKI overexpression in PCa increased sensitivity to ACSL4-mediated ferroptosis by statins. This explains the epidemiological associations between hyperlipidemia and PCa, and will guide molecular subtype-driven drug repurposing studies. Citation Format: Hyun Ho Han, Jin Sol Sung, Dong Wook Song, Cheol Keun Park, Nam Hoon Cho, Young Deuk Choi, Woo Jin Ko. Hyperlipidemia promotes aggressive variant prostate cancer via RNA-binding protein Quaking [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2270.

RNA-binding protein QKI suppresses breast cancer via RASA1/MAPK signaling pathway.

BackgroundRNA-binding protein Quaking (QKI) has been linked with the pathogenesis and development of various human malignancies. Herein, we explored the particular role of QKI in breast cancer (BC) progression.MethodsThe methods employed in the study included public dataset analysis, western blot, quantitative real-time PCR (qRT-PCR), cell count kit-8 (CCK8) assay, colony formation assay, flow cytometric analysis, RNA immunoprecipitation (RIP), messenger RNA (mRNA) stability assay, QKI overexpression and knockdown, and Ras p21 protein activator 1 (RASA1) knockdown.ResultsAberrant expression levels of QKI and RASA1 were detected in BC and compared with those in noncancerous tissues. A moderately positive correlation between QKI and RASA1 was verified within BC tissues. Low expression of QKI was associated with positive estrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor 2 (HER2) status, non-triple-negative breast cancer (TNBC), non-basal-like BC, and poor clinical outcomes in BC patients. QKI overexpression suppressed BC cell proliferation and colony formation, and arrested cell cycle at G1 phase. RIP assay and mRNA stability assay confirmed that QKI directly bound to RASA1 transcript and increased its stability, thus inactivating the MAPK pathway and inhibiting BC progression. RASA1 knockdown could partly attenuate the inhibitory effect of QKI on BC cell proliferation via activating the mitogen-activated protein kinase (MAPK) pathway.ConclusionsQKI, which was frequently downregulated in BC, could significantly inhibit cell proliferation and arrest cell cycle at G1 phase by binding and enhancing RASA1 mRNA expression. Low expression of QKI was prominently associated with unfavorable clinical outcomes in BC patients, indicating the prognostic value of QKI in BC.

QUAKING Regulates Microexon Alternative Splicing of the Rho GTPase Pathway and Controls Microglia Homeostasis

The role of RNA binding proteins in regulating the phagocytic and cytokine-releasing functions of microglia is unknown. Here, we show that microglia deficient for the QUAKING (QKI) RNA binding protein have increased proinflammatory cytokine release and defects in processing phagocytosed cargo. Splicing analysis reveals a role for QKI in regulating microexon networks of the Rho GTPase pathway. We show an increase in RhoA activation and proinflammatory cytokines in QKI-deficient microglia that are repressed by treating with a Rock kinase inhibitor. During the cuprizone diet, mice with QKI-deficient microglia are inefficient at supporting central nervous system (CNS) remyelination and cause the recruited oligodendrocyte precursor cells to undergo apoptosis. Furthermore, the expression of QKI in microglia is downregulated in preactive, chronic active, and remyelinating white matter lesions of multiple sclerosis (MS) patients. Overall, our findings identify QKI as an alternative splicing regulator governing a network of Rho GTPase microexons with implications for CNS remyelination and MS patients.

Comprehensive analysis of neuronal guidance cue expression regulation during monocyte-to-macrophage differentiation reveals post-transcriptional regulation of semaphorin7A by the RNA-binding protein quaking.

In response to inflammatory cytokines and chemokines, monocytes differentiate into macrophages. Comprehensive analysis of gene expression regulation of neuronal guidance cue (NGC) ligands and receptors in the monocyte-to-macrophage differentiation process is not available yet. We performed transcriptome profiling in both human primary PBMCs/PBMC-derived macrophages and THP-1 cells/THP-1-macrophages using microarray or RNA sequencing methods. Pathway analysis showed that the axonal guidance pathway is significantly regulated upon monocyte differentiation. We confirmed NGC ligands and receptors which were consistently regulated, including SEMA4D, SEMA7A, NRP1, NRP2, PLXNA1 and PLXNA3. The involvement of RNA-binding protein quaking (QKI) in the regulation of NGC expression was investigated using monocytes and macrophages from a QKI haplo-insufficient patient and her healthy sibling. This revealed a positive correlation of SEMA7A expression with QKI expression. In silico analysis of 3′UTRs of NGCs proposed the competitive binding of QKI to proximal microRNA targeting sites as the mechanism of QKI-dependent regulation of SEMA7A. RNA immunoprecipitation confirmed an interaction of QKI with the 3′UTR of SEMA7A. Loss of SEMA7A resulted in monocyte differentiation towards a more anti-inflammatory macrophage. Taken together, the axonal guidance pathway is regulated during monocyte-to-macrophage differentiation, and the regulation is in line with the necessary functional adaption for the specialised role of macrophages.

Long non-coding RNA Loc490 inhibits gastric cancer cell proliferation and metastasis by upregulating RNA-binding protein Quaking.

Gastric cancer (GC) is one of the most common malignant tumor types worldwide. Long non-coding RNAs (lncRNAs) have important epigenetic effects, including altering the proliferation and metastasis of malignant tumors. We used gene chip technology to search for lncRNAs that were differentially expressed in GC and metastatic lymph node tissues compared with adjacent normal tissues. The lncRNA Loc490 and the RNA-binding protein Quaking (QKI) were downregulated in GC tissues and lymph node metastases compared with normal tissues, and the levels of these two genes correlated positively with one another. Loc490 expression correlated negatively with lymph node metastasis and vein/nerve invasion, while it correlated positively with overall and disease-free survival. In vitro, Loc490 post-translationally enhanced the expression of QKI and suppressed the expression of epithelial-mesenchymal transition-related molecules. Overexpression of Loc490 inhibited GC cell proliferation, invasion and metastasis and exerted strong antitumor effects in vivo, while silencing of QKI antagonized these effects. A potential binding site between Loc490 and QKI was detected through bioinformatics analysis and confirmed through RNA immunoprecipitation and mutant analyses. Our results suggest that lncRNA Loc490 inhibits GC cell proliferation and metastasis by upregulating RNA-binding protein QKI.

Salidroside Attenuates Doxorubicin-Induced Cardiac Dysfunction Partially Through Activation of QKI/FoxO1 Pathway.

Doxorubicin (DOX) is an effective chemotherapy. However, its usage has been associated with adverse effects. Salidroside (SAL) is an antioxidative drug, which confers protective effects against several diseases. Salidroside can attenuate cardiac dysfunction induced by DOX. Quaking (QKI) is identified as a protective factor that can inhibit cardiotoxicity medicated by DOX through the regulation of cardiac circular RNA expression. The present study investigated the role of QKI on the protective effect of SAL in the DOX-induced cardiotoxicity model. Results indicated that SAL attenuated DOX-induced adverse effects, including cardiac dysfunction, weight loss, and reactive oxygen species (ROS) production, and decreased the expression of BAX, caspase 3, and FoxO1. Also, it increased the Mn-SOD2 and QKI expression in vivo and in vitro. Furthermore, QKI knockdown suppressed anti-cardiotoxicity mediated by SAL. In conclusion, the results of the current study show that salidroside attenuates doxorubicin-induced cardiac dysfunction through activation of QKI/FoxO1 pathway.

RNA‐Binding Protein QKI is a critical pre‐RNA splicing regulator for cardiac development and function

RNA‐binding protein QKI (also known as Quaking) belongs to hnRNP K‐homology (KH)‐domain protein family and is implicated a novel regulator in pre‐RNA splicing. As previously shown, the QKI homolog how potentially regulates heart lumen formation and function in fruit fly. However, QKI’s function in mammalian heart development is largely unknown. We found that Qki specifically expressed in mouse developing hearts as early as E7.0 and this high‐level expression was maintained in the hearts to adulthood. Consistent with this finding, by using human embryonic stem cells (hESCs)‐cardiomyocyte differentiation system, QKI expression was found up‐regulated at Day 6, a critical time frame that cardiogenic progenitor transition into early cardiomyocytes. To determine the biological function of QKI in cardiogenesis, we generated hESCsQKIdef by using CRISPR/Cas9 gene editing technology and analyzed the physiological impact of QKI‐deficiency to cardiomyocyte differentiation and maturation. As expected, we did not find defect in pluripotency in hESCsQKIdef, but the contractile function was dramatically reduced in hESCsQKIdef‐derived cardiomyocytes. Based on scRNA‐seq and clustering analyses, there was no significant difference in the distribution of the clusters when compared hESCsQKIdef‐cardiomyocyte group to normal control group, suggesting that the cardiomyocyte differentiation was largely unaffected in hESCsQKIdef. However, scRNA‐seq demonstrated a handful of genes encoding sarcomere proteins were significantly altered in cardiomyocyte clusters, which included ACTN2, ACTA1, MYH7, and MYL2, etc., indicating a significant defect in cardiomyocyte maturation. Bulk RNA‐seq data not only further confirmed this notion, but also provided additional depth for detailed analysis on the QKI‐mediated pre‐RNA splicing events. In conjunction with QKI‐binding motif search and RNA immunoprecipitation (RIP) analysis, we were able to demonstrate that QKI was a key pre‐RNA splicing regulator for sets of genes involved in cardiac myofibrillogenesis and cardiac excitation‐contraction (E‐C) coupling, which ultimately impacted on cardiomyocyte maturation and function. Additional analysis of cardiac developmental defects in Qkibgeo mutant mice further validated that QKI was an indispensable splicing regulator in cardiovascular development. Our results not only revealed a novel mechanism by which QKI regulates pre‐mRNA splicing in cardiogenesis, but also implied that QKI was likely involved in the pathogenesis of certain forms of congenital heart defects and cardiomyopathies.Support or Funding InformationThis work was supported in part by National Institute of Health P01HL134599

MiR-362-5p, Which Is Regulated by Long Non-Coding RNA MBNL1-AS1, Promotes the Cell Proliferation and Tumor Growth of Bladder Cancer by Targeting QKI.

In this study, we found miR-362-5p was upregulated in bladder cancer tissues and we predicted that QKI is potential a target of miR-362-5p and MBNL1-AS1 might be able to directly target to miR-362-5p. We attempted to evaluate whether miR-362-5p could play its roles in bladder cancer through regulating QKI (quaking) and whether the expression and function of miR-362-5p could be mediated by lncRNA MBNL1-AS1. We performed the gain- and loss-function experiments to explore the association between miR-362-5p expression and bladder cancer proliferation. In vivo, the nude mice were injected with miR-362-5p knockdown SW780 cells to assess the effects of miR-362-5p on tumor growth. The results showed upregulation of miR-362-5p promoted cell proliferation of bladder cancer cells. MBNL1-AS1 and QKI could directly bind with miR-362-5p, and knockdown of MBNL1-AS1 or QKI could abrogate the regulatory effects of miR-362-5p on bladder cancer cell proliferation. Furthermore, downregulation of miR-362-5p inhibited bladder tumor growth and increased QKI expression. Our data unveiled that miR-362-5p may play an oncogenic role in bladder cancer through QKI and MBNL1-AS1 might function as a sponge to mediate the miR-362-5p expression and function.

Targeting the RNA-Binding Protein QKI in Myeloid Cells Ameliorates Macrophage-Induced Renal Interstitial Fibrosis.

In the pathophysiologic setting of acute and chronic kidney injury, the excessive activation and recruitment of blood-borne monocytes prompts their differentiation into inflammatory macrophages, a process that leads to progressive glomerulosclerosis and interstitial fibrosis. Importantly, this differentiation of monocytes into macrophages requires the meticulous coordination of gene expression at both the transcriptional and post-transcriptional level. The transcriptomes of these cells are ultimately determined by RNA-binding proteins such as QUAKING (QKI), that define their pre-mRNA splicing and mRNA transcript patterns. Using two mouse models, namely (1) quaking viable mice (qkv) and (2) the conditional deletion in the myeloid cell lineage using the lysozyme 2-Cre (QKIFL/FL;LysM-Cre mice), we demonstrate that the abrogation of QKI expression in the myeloid cell lineage reduces macrophage infiltration following kidney injury induced by unilateral urethral obstruction (UUO). The qkv and QKIFL/FL;LysM-Cre mice both showed significant diminished interstitial collagen deposition and fibrosis in the UUO-damaged kidney, as compared to wild-type littermates. We show that macrophages isolated from QKIFL/FL;LysM-Cre mice are associated with defects in pre-mRNA splicing. Our findings demonstrate that reduced expression of the alternative splice regulator QKI in the cells of myeloid lineage attenuates renal interstitial fibrosis, suggesting that inhibition of this splice regulator may be of therapeutic value for certain kidney diseases.

QKI, a miR-200 target gene, suppresses epithelial-to-mesenchymal transition and tumor growth.

The microRNA-200 (miR-200) family plays a major role in specifying epithelial phenotype by preventing expression of the transcription repressors ZEB1 and ZEB2, which are well-known regulators of the epithelial-to-mesenchymal transition (EMT) in epithelial tumors including oral squamous cell carcinoma (OSCC). Here, we elucidated whether miR-200 family members control RNA-binding protein quaking (QKI), a newly identified tumor suppressor that is regulated during EMT. We predicted that miR-200a and miR-200b could recognize QKI 3'-UTR by analyzing TargetScan and The Cancer Genome Atlas head and neck squamous cell carcinoma (HNSCC) dataset. Forced expression of miR-200b/a/429 inhibited expression of ZEB1/2 and decreased cell migration in OSCC cell lines CAL27 and HSC3. QKI expression was also suppressed by miR-200 overexpression, and the 3'-UTR of QKI mRNA was directly targeted by miR-200 in luciferase reporter assays. Interestingly, shRNA-mediated knockdown of QKI led to pronounced EMT and protumor effects in both in vitro and in vivo studies of OSCC. Furthermore, high expression of QKI protein is associated with favorable prognosis in surgically resected HNSCC and lung adenocarcinoma. In conclusion, QKI increases during EMT and is targeted by miR-200; while, it suppresses EMT and tumorigenesis. We suggest that QKI and miR-200 form a negative feedback loop to maintain homeostatic responses to EMT-inducing signals.

Quaking orchestrates a post-transcriptional regulatory network of endothelial cell cycle progression critical to angiogenesis and metastasis.

Angiogenesis is critical to cancer development and metastasis. However, anti-angiogenic agents have only had modest therapeutic success, partly due to an incomplete understanding of tumor endothelial cell (EC) biology. We previously reported that the microRNA (miR)-200 family inhibits metastasis through regulation of tumor angiogenesis, but the underlying molecular mechanisms are poorly characterized. Here, using integrated bioinformatics approaches, we identified the RNA-binding protein (RBP) quaking (QKI) as a leading miR-200b endothelial target with previously unappreciated roles in the tumor microenvironment in lung cancer. In lung cancer samples, both miR-200b suppression and QKI overexpression corresponded with tumor ECs relative to normal ECs, and QKI silencing phenocopied miR-200b-mediated inhibition of sprouting. Additionally, both cancer cell and endothelial QKI expression in patient samples significantly corresponded with poor survival and correlated with angiogenic indices. QKI supported EC function by stabilizing cyclin D1 (CCND1) mRNA to promote EC G1/S cell cycle transition and proliferation. Both nanoparticle-mediated RNA interference of endothelial QKI expression and palbociclib blockade of CCND1 function potently inhibited metastasis in concert with significant effects on tumor vasculature. Altogether, this work demonstrates the clinical relevance and therapeutic potential of a novel, actionable miR/RBP axis in tumor angiogenesis and metastasis.

Androgen receptor‑mediated upregulation of quaking affects androgen receptor‑related prostate cancer development and anti‑androgen receptor therapy.

The androgen receptor (AR) has a crucial role in prostate cancer. RNA-binding protein-mediated post-transcriptional regulation is important in the initiation and development of cancer. The present study attempted to elucidate the mutual association of AR and RNA-binding protein quaking (QKI) in the development of prostate cancer. Dual-luciferase reporter demonstrated that AR can positively regulate the expression of QKI in prostate cancer cell lines due to its effective transcription regulating function. In addition, QKI may increase expression of AR by heat shock protein 90, which is a coactivator of AR, and silencing QKI can increase the sensitive of Casodex, which is an antagonist of AR in castration-resistant prostate cancer. This may be a new strategy for advanced prostate cancer.