Nsp1 facilitates SARS-CoV-2 replication through calcineurin-NFAT signaling

SARS-CoV-2, the causative agent of COVID-19, has been intensely studied in search of effective antiviral treatments. The immunosuppressant cyclosporine A (CsA) has been suggested to be a pan-coronavirus inhibitor, yet its underlying mechanism remained largely unknown. Here, we found that non-structural protein 1 (Nsp1) of SARS-CoV-2 usurped CsA-suppressed nuclear factor of activated T cells (NFAT) signaling to drive the expression of cellular DEAD-box helicase 5 (DDX5), which facilitates viral replication. Nsp1 interacted with calcineurin A (CnA) to displace the regulatory protein regulator of calcineurin 3 (RCAN3) of CnA for NFAT activation. The influence of NFAT activation on SARS-CoV-2 replication was also validated by using the Nsp1-deficient mutant virus. Calcineurin inhibitors, such as CsA and VIVIT, inhibited SARS-CoV-2 replication and exhibited synergistic antiviral effects when used in combination with nirmatrelvir. Our study delineated the molecular mechanism of CsA-mediated inhibition of SARS-CoV-2 replication and the anti-SARS-CoV-2 action of calcineurin inhibitors.

IMPORTANCE

Cyclosporine A (CsA), commonly used to inhibit immune responses, is also known to have anti-SARS-CoV-2 activity, but its mode of action remains elusive. Here, we provide a model to explain how CsA antagonizes SARS-CoV-2 through three critical proteins: DDX5, NFAT1, and Nsp1. DDX5 is a cellular facilitator of SARS-CoV-2 replication, and NFAT1 controls the production of DDX5. Nsp1 is a viral protein absent from the mature viral particle and capable of activating the function of NFAT1 and DDX5. CsA and similar agents suppress Nsp1, NFAT1, and DDX5 to exert their anti-SARS-CoV-2 activity either alone or in combination with Paxlovid.

DEAD box RNA helicase 5 is a new pro-viral host factor for Sindbis virus infection

BACKGROUND

RNA helicases are emerging as key factors regulating host-virus interactions. The DEAD-box ATP-dependent RNA helicase DDX5, which plays an important role in many aspects of cellular RNA biology, was also found to either promote or inhibit viral replication upon infection with several RNA viruses. Here, our aim is to examine the impact of DDX5 on Sindbis virus (SINV) infection.

METHODS

We analysed the interaction between DDX5 and the viral RNA using imaging and RNA-immunoprecipitation approaches. The interactome of DDX5 in mock- and SINV-infected cells was determined by mass spectrometry. We validated the interaction between DDX17 and the viral capsid by co- immunoprecipitation in the presence or absence of an RNase treatment. We determined the subcellular localization of DDX5, its cofactor DDX17 and the viral capsid protein by co-immunofluorescence. Finally, we investigated the impact of DDX5 depletion and overexpression on SINV infection at the viral protein, RNA and infectious particle accumulation level. The contribution of DDX17 was also tested by knockdown experiments.

RESULTS

In this study we demonstrate that DDX5 interacts with the SINV RNA during infection. Furthermore, the proteomic analysis of the DDX5 interactome in mock and SINV-infected HCT116 cells identified new cellular and viral partners and confirmed the interaction between DDX5 and DDX17. Both DDX5 and DDX17 re-localize from the nucleus to the cytoplasm upon SINV infection and interact with the viral capsid protein. We also show that DDX5 depletion negatively impacts the viral replication cycle, while its overexpression has a pro-viral effect. Finally, we observed that DDX17 depletion reduces SINV infection, an effect which is even more pronounced in a DDX5-depleted background, suggesting a synergistic pro-viral effect of the DDX5 and DDX17 proteins on SINV.

CONCLUSIONS

These results not only shed light on DDX5 as a novel and important host factor to the SINV life cycle, but also expand our understanding of the roles played by DDX5 and DDX17 as regulators of viral infections.

FL118 Is a Potent Therapeutic Agent against Chronic Myeloid Leukemia Resistant to BCR-ABL Inhibitors through Targeting RNA Helicase DDX5

Chronic myeloid leukemia (CML) is induced by the expression of the fused tyrosine kinase BCR-ABL, which is caused by a chromosomal translocation. BCR-ABL inhibitors have been used to treat CML; however, the acquisition of resistance by CML cells during treatment is a serious issue. We herein demonstrated that BCR-ABL induced the expression of the RNA helicase DDX5 in K562 cells derived from CML patients in a manner that was dependent on its kinase activity, which resulted in cell proliferation and survival. The knockout of DDX5 decreased the expression of BIRC5 (survivin) and activated caspase 3, leading to apoptosis in K562 cells. Similar results were obtained in cells treated with FL118, an inhibitor of DDX5 and a derivative compound of camptothecin (CPT). Furthermore, FL118 potently induced apoptosis not only in Ba/F3 cells expressing BCR-ABL, but also in those expressing the BCR-ABL T315I mutant, which is resistant to BCR-ABL inhibitors. Collectively, these results revealed that DDX5 is a critical therapeutic target in CML and that FL118 is an effective candidate compound for the treatment of BCR-ABL inhibitor-resistant CML.

RNA helicase DDX5 is involved in R-loop dynamics of preimplantation embryos

Objective

R-loops are DNA:RNA triplex hybrids, and their metabolism is tightly regulated by transcriptional regulation, DNA damage response, and chromatin structure dynamics. R-loop homeostasis is dynamically regulated and closely associated with gene transcription in mouse zygotes. However, the factors responsible for regulating these dynamic changes in the R-loops of fertilized mouse eggs have not yet been investigated. This study examined the functions of candidate factors that interact with R-loops during zygotic gene activation.

Methods

In this study, we used publicly available next-generation sequencing datasets, including low-input ribosome profiling analysis and polymerase II chromatin immunoprecipitation-sequencing (ChIP-seq), to identify potential regulators of R-loop dynamics in zygotes. These datasets were downloaded, reanalyzed, and compared with mass spectrometry data to identify candidate factors involved in regulating R-loop dynamics. To validate the functions of these candidate factors, we treated mouse zygotes with chemical inhibitors using in vitro fertilization. Immunofluorescence with an anti-R-loop antibody was then performed to quantify changes in R-loop metabolism.

Results

We identified DEAD-box-5 (DDX5) and histone deacetylase-2 (HDAC2) as candidates that potentially regulate R-loop metabolism in oocytes, zygotes and two-cell embryos based on change of their gene translation. Our analysis revealed that the DDX5 inhibition of activity led to decreased R-loop accumulation in pronuclei, indicating its involvement in regulating R-loop dynamics. However, the inhibition of histone deacetylase-2 activity did not significantly affect R-loop levels in pronuclei.

Conclusion

These findings suggest that dynamic changes in R-loops during mouse zygote development are likely regulated by RNA helicases, particularly DDX5, in conjunction with transcriptional processes. Our study provides compelling evidence for the involvement of these factors in regulating R-loop dynamics during early embryonic development.

DEAD-Box Helicase 17 exacerbates non-alcoholic steatohepatitis via transcriptional repression of cyp2c29, inducing hepatic lipid metabolism disorder and eliciting the activation of M1 macrophages

OBJECTIVE

Our study was to elucidate the role of RNA helicase DEAD-Box Helicase 17 (DDX17) in NAFLD and to explore its underlying mechanisms.

METHODS

We created hepatocyte-specific Ddx17-deficient mice aim to investigate the impact of Ddx17 on NAFLD induced by a high-fat diet (HFD) as well as methionine and choline-deficient l-amino acid diet (MCD) in adult male mice. RNA-seq and lipidomic analyses were conducted to depict the metabolic landscape, and CUT&Tag combined with chromatin immunoprecipitation (ChIP) and luciferase reporter assays were conducted.

RESULTS

In this work, we observed a notable increase in DDX17 expression in the livers of patients with NASH and in murine models of NASH induced by HFD or MCD. After introducing lentiviruses into hepatocyte L02 for DDX17 knockdown or overexpression, we found that lipid accumulation induced by palmitic acid/oleic acid (PAOA) in L02 cells was noticeably weakened by DDX17 knockdown but augmented by DDX17 overexpression. Furthermore, hepatocyte-specific DDX17 knockout significantly alleviated hepatic steatosis, inflammatory response and fibrosis in mice after the administration of MCD and HFD. Mechanistically, our analysis of RNA-seq and CUT&Tag results combined with ChIP and luciferase reporter assays indicated that DDX17 transcriptionally represses Cyp2c29 gene expression by cooperating with CCCTC binding factor (CTCF) and DEAD-Box Helicase 5 (DDX5). Using absolute quantitative lipidomics analysis, we identified a hepatocyte-specific DDX17 deficiency that decreased lipid accumulation and altered lipid composition in the livers of mice after MCD administration. Based on the RNA-seq analysis, our findings suggest that DDX17 could potentially have an impact on the modulation of lipid metabolism and the activation of M1 macrophages in murine NASH models.

CONCLUSION

These results imply that DDX17 is involved in NASH development by promoting lipid accumulation in hepatocytes, inducing the activation of M1 macrophages, subsequent inflammatory responses and fibrosis through the transcriptional repression of Cyp2c29 in mice. Therefore, DDX17 holds promise as a potential drug target for the treatment of NASH.

DDX5 inhibits inflammation by modulating m6A levels of TLR2/4 transcripts during bacterial infection

DExD/H-box helicases are crucial regulators of RNA metabolism and antiviral innate immune responses; however, their role in bacteria-induced inflammation remains unclear. Here, we report that DDX5 interacts with METTL3 and METTL14 to form an m6A writing complex, which adds N6-methyladenosine to transcripts of toll-like receptor (TLR) 2 and TLR4, promoting their decay via YTHDF2-mediated RNA degradation, resulting in reduced expression of TLR2/4. Upon bacterial infection, DDX5 is recruited to Hrd1 at the endoplasmic reticulum in an MyD88-dependent manner and is degraded by the ubiquitin-proteasome pathway. This process disrupts the DDX5 m6A writing complex and halts m6A modification as well as degradation of TLR2/4 mRNAs, thereby promoting the expression of TLR2 and TLR4 and downstream NF-κB activation. The role of DDX5 in regulating inflammation is also validated in vivo, as DDX5- and METTL3-KO mice exhibit enhanced expression of inflammatory cytokines. Our findings show that DDX5 acts as a molecular switch to regulate inflammation during bacterial infection and shed light on mechanisms of quiescent inflammation during homeostasis.

Ribosomal protein L24 mediates mammalian microRNA processing in an evolutionarily conserved manner

To investigate the mechanism(s) underlying the expression of primate-specific microRNAs (miRs), we sought DNA regulatory elements and proteins mediating expression of the primate-specific hsa-miR-608 (miR-608), which is located in the SEMA4G gene and facilitates the cholinergic blockade of inflammation by targeting acetylcholinesterase mRNA. 'Humanized' mice carrying pre-miR-608 flanked by 250 bases of endogenous sequences inserted into the murine Sema4g gene successfully expressed miR-608. Moreover, by flanking miR-608 by shortened fragments of its human genome region we identified an active independent promoter within the 150 nucleotides 5' to pre-miR-608, which elevated mature miR-608 levels by 100-fold in transfected mouse- and human-originated cells. This highlighted a regulatory role of the 5' flank as enabling miR-608 expression. Moreover, pull-down of the 150-base 5' sequence revealed its interaction with ribosomal protein L24 (RPL24), implicating an additional mechanism controlling miR-608 levels. Furthermore, RPL24 knockdown altered the expression of multiple miRs, and RPL24 immunoprecipitation indicated that up- or down-regulation of the mature miRs depended on whether their precursors bind RPL24 directly. Finally, further tests showed that RPL24 interacts directly with DDX5, a component of the large microprocessor complex, to inhibit miR processing. Our findings reveal that RPL24, which has previously been shown to play a role in miR processing in Arabidopsis thaliana, has a similar evolutionarily conserved function in miR biogenesis in mammals. We thus characterize a novel extra-ribosomal role of RPL24 in primate miR regulation.

VAMP8 suppresses the metastasis via DDX5/β-catenin signal pathway in osteosarcoma

Osteosarcoma is a highly metastatic malignant bone tumor, necessitating the development of new treatments to target its metastasis. Recent studies have revealed the significance of VAMP8 in regulating various signaling pathways in various types of cancer. However, the specific functional role of VAMP8 in osteosarcoma progression remains unclear. In this study, we observed a significant downregulation of VAMP8 in osteosarcoma cells and tissues. Low levels of VAMP8 in osteosarcoma tissues were associated with patients' poor prognosis. VAMP8 inhibited the migration and invasion capability of osteosarcoma cells. Mechanically, we identified DDX5 as a novel interacting partner of VAMP8, and the conjunction of VAMP8 and DDX5 promoted the degradation of DDX5 via the ubiquitin-proteasome system. Moreover, reduced levels of DDX5 led to the downregulation of β-catenin, thereby suppressing the epithelial-mesenchymal transition (EMT). Additionally, VAMP8 promoted autophagy flux, which may contribute to the suppression of osteosarcoma metastasis. In conclusion, our study anticipated that VAMP8 inhibits osteosarcoma metastasis by promoting the proteasomal degradation of DDX5, consequently inhibiting WNT/β-catenin signaling and EMT. Dysregulation of autophagy by VAMP8 is also implicated as a potential mechanism. These findings provide new insights into the biological nature driving osteosarcoma metastasis and highlight the modulation of VAMP8 as a potential therapeutic strategy for targeting osteosarcoma metastasis.

DDX5 Functions as a Tumor Suppressor in Tongue Cancer

DEAD-box polypeptide 5 (DDX5), a DEAD-box RNA helicase, is a multifunctional protein that plays important roles in many physiological and pathological processes. Contrary to its documented oncogenic role in a wide array of cancers, we herein demonstrate that DDX5 serves as a tumor suppressor in tongue cancer. The high expression of DDX5 is correlated with better prognosis for clinical tongue cancer patients. DDX5 downregulates the genes associated with tongue cancer progression. The knockdown of DDX5 promotes, while the overexpression of DDX5 inhibits, tongue cancer proliferation, development, and cisplatin resistance. Furthermore, the expression of DDX5 in tongue cancer is associated with immune cell infiltration in the tumor microenvironment. Specifically, the expression of DDX5 is associated with the reduced infiltration of M2 macrophages and increased infiltration of T cell clusters, which may contribute to anticancer effects in the tumor microenvironment. In this study, we establish DDX5 as a valuable prognostic biomarker and an important tumor suppressor in tongue cancer.

Role of the DEAD-box RNA helicase DDX5 (p68) in cancer DNA repair, immune suppression, cancer metabolic control, virus infection promotion, and human microbiome (microbiota) negative influence

There is increasing evidence indicating the significant role of DDX5 (also called p68), acting as a master regulator and a potential biomarker and target, in tumorigenesis, proliferation, metastasis and treatment resistance for cancer therapy. However, DDX5 has also been reported to act as an oncosuppressor. These seemingly contradictory observations can be reconciled by DDX5's role in DNA repair. This is because cancer cell apoptosis and malignant transformation can represent the two possible outcomes of a single process regulated by DDX5, reflecting different intensity of DNA damage. Thus, targeting DDX5 could potentially shift cancer cells from a growth-arrested state (necessary for DNA repair) to apoptosis and cell killing. In addition to the increasingly recognized role of DDX5 in global genome stability surveillance and DNA damage repair, DDX5 has been implicated in multiple oncogenic signaling pathways. DDX5 appears to utilize distinct signaling cascades via interactions with unique proteins in different types of tissues/cells to elicit opposing roles (e.g., smooth muscle cells versus cancer cells). Such unique features make DDX5 an intriguing therapeutic target for the treatment of human cancers, with limited low toxicity to normal tissues. In this review, we discuss the multifaceted functions of DDX5 in DNA repair in cancer, immune suppression, oncogenic metabolic rewiring, virus infection promotion, and negative impact on the human microbiome (microbiota). We also provide new data showing that FL118, a molecular glue DDX5 degrader, selectively works against current treatment-resistant prostate cancer organoids/cells. Altogether, current studies demonstrate that DDX5 may represent a unique oncotarget for effectively conquering cancer with minimal toxicity to normal tissues.

DDX5 inhibits type I IFN production by promoting degradation of TBK1 and disrupting formation of TBK1 - TRAF3 complex

DExD/H-box helicase (DDX) 5 belongs to the DExD/H-box helicase family. DDX family members play differential roles in the regulation of innate antiviral immune response. However, whether DDX5 is involved in antiviral immunity remains unclear. In this study, we found that DDX5 serves as a negative regulator of type I interferon (IFN) response. Overexpression of DDX5 inhibited IFN production induced by Spring viremia of carp virus (SVCV) and poly(I:C) and enhanced virus replication by targeting key elements of the RLR signaling pathway (MAVS, MITA, TBK1, IRF3 and IRF7). Mechanistically, DDX5 directly interacted with TBK1 to promote its autophagy-mediated degradation. Moreover, DDX5 was shown to block the interaction between TRAF3 and TBK1, hence preventing nuclear translocation of IRF3. Together, these data shed light on the roles of DDX5 in regulating IFN response.

Corrigendum: DDX5 and DDX17-multifaceted proteins in the regulation of tumorigenesis and tumor progression

[This corrects the article DOI: 10.3389/fonc.2022.943032.].

Hypoxia-mediated regulation of DDX5 through decreased chromatin accessibility and post-translational targeting restricts R-loop accumulation

Local hypoxia occurs in most solid tumors and is associated with aggressive disease and therapy resistance. Widespread changes in gene expression play a critical role in the biological response to hypoxia. However, most research has focused on hypoxia-inducible genes as opposed to those which are decreased in hypoxia. We demonstrate that chromatin accessibility is decreased in hypoxia, predominantly at gene promoters and specific pathways are impacted including DNA repair, splicing and the R-loop interactome. One of the genes with decreased chromatin accessibility in hypoxia was DDX5, encoding the RNA helicase, DDX5, which showed reduced expression in various cancer cell lines in hypoxic conditions, tumor xenografts and in patient samples with hypoxic tumors. Most interestingly, we found that when DDX5 is rescued in hypoxia, replication stress and R-loop levels accumulate further, demonstrating that hypoxia-mediated repression of DDX5 restricts R-loop accumulation. Together these data support the hypothesis that a critical part of the biological response to hypoxia is the repression of multiple R-loop processing factors, however, as shown for DDX5, their role is specific and distinct.

PARP1 controls the transcription of CD24 by ADP-ribosylating the RNA helicase DDX5 in pancreatic cancer

The PARP1 protein plays a key role in DNA damage repair and ADP-ribosylation to regulate gene expression. Strategies to target PARP1 have rapidly been developed for cancer treatment. However, the role of the innate immune response in targeted anti-PARP1 therapy remains poorly understood. In this work, we aimed to elucidate the regulatory mechanism underlying the immunogenicity of PARP1 and explore efficient therapeutic strategies to enhance the antitumor effect of PARP inhibitors. The relationships between PARP1 expression and immunosuppressive factors were examined by qRTPCR and immunoblot analysis. DNA pull-down, chromatin immunoprecipitation-quantitative PCR (ChIPqPCR) and luciferase reporter assays were employed to reveal the mechanism by which the expression of the immune checkpoint regulator CD24 is regulated by PARP1. Phagocytosis assays and pancreatic cancer animal models were applied to evaluate the therapeutic effect of simultaneous disruption of PARP1 and the antiphagocytic factor CD24. Upregulation of the innate immunosuppressive factor CD24 was observed in pancreatic cancer during PARP1 inhibition. The activating effect of targeting CD24 on macrophage phagocytosis was verified. Then, we showed that PARP1 attenuated the transcription of CD24 by ADP-ribosylating the transcription factor DDX5 in pancreatic cancer. Combined blockade of PARP1 and the antiphagocytic factor CD24 elicited a synergetic antitumor effect in pancreatic cancer. Our research provided evidence that combination treatment with PARP inhibitors and CD24 blocking monoclonal antibodies (mAbs) could be an effective strategy to improve the clinical therapeutic response in pancreatic cancer.

Identification of DDX5 as an indispensable activator of the glucocorticoid receptor in adipocyte differentiation

The expression of CCAAT/enhancer-binding protein (C/EBP) family members and peroxisome proliferator-activated receptor γ (PPAR γ) is essential for the differentiation of pre-adipocyte 3T3-L1 cells into mature adipocytes induced by a combined stimulation with dexamethasone, 3-isobutyl-1-methylxanthine and insulin (DMI). We herein demonstrated that the RNA helicase DDX5, the expression of which was induced by DMI, played an important role in the adipocyte differentiation of 3T3-L1 cells. The DMI-induced accumulation of lipid droplets and expression of adipocyte markers in 3T3-L1 cells were significantly inhibited by the knockdown of DDX5. The knockdown of DDX5 interfered with the expressional induction of C/EBPδ, which was the first to be induced in the transcription factor cascade, and inhibited the subsequent expression of the other transcription factors, C/EBPβ, PPARγ and C/EBPα. DDX5 interacted with the glucocorticoid receptor (GR), which induced the expression of C/EBPδ. The knockdown of DDX5 failed to induce the nuclear translocation of GR, suggesting the essential role of DDX5 in the early stage of adipocyte differentiation. Furthermore, the reconstitution of DDX5, but not the DDX5 mutant (K144N) lacking RNA helicase activity, restored DMI-induced GR activation and adipocyte differentiation in 3T3-L1 cells in which DDX5 was knocked down, confirming that the RNA helicase activity of DDX5 is essential for adipogenesis. Collectively, these results revealed for the first time that DDX5 is necessary for GR activation and plays an essential role in early adipocyte differentiation.

The indispensable role of the RNA helicase DDX5 in tumorigenesis induced by the myeloproliferative neoplasm-associated JAK2V617F mutant

A point mutation (V617F) in the Janus kinase 2 (JAK2) gene results in the production of disorderly activated tyrosine kinase, which causes myeloproliferative neoplasms (MPN). We herein demonstrated that the RNA helicase DDX5 was highly expressed at the mRNA and protein levels through the activation of signal transducer and activator of transcription 5 (STAT5) in Ba/F3 cells expressing a JAK2V617F mutant and erythropoietin receptor (V617F/EpoR cells) and MPN patient-derived HEL cells. A treatment with the JAK1/2 inhibitor, ruxolitinib and STAT5 inhibitor, pimozide significantly inhibited DDX5 mRNA expression and enhanced the degradation of DDX5 in these cells, suggesting that the JAK2V617F mutant positively regulates DDX5 mRNA expression and DDX5 protein stability by activating STAT5. The knockdown of DDX5 specifically inhibited the activation of mechanistic target of rapamycin (mTOR) in V617F/EpoR cells and HEL cells and significantly suppressed the proliferation of these cells. Furthermore, the knockdown of DDX5 markedly suppressed tumorigenesis, splenomegaly, and liver hypertrophy caused by an inoculation of V617F/EpoR cells in nude mice. Collectively, these results revealed that JAK2V617F exhibits transforming activity by inducing the expression of DDX5 in a STAT5-dependent manner, indicating the potential of the JAK2V617F/STAT5/DDX5 axis as a therapeutic target in the treatment of MPN.

DDX5 mRNA-targeting antisense oligonucleotide as a new promising therapeutic in combating castration-resistant prostate cancer

The heat shock protein 27 (Hsp27) has emerged as a principal factor of the castration-resistant prostate cancer (CRPC) progression. Also, an antisense oligonucleotide (ASO) against Hsp27 (OGX-427 or apatorsen) has been assessed in different clinical trials. Here, we illustrate that Hsp27 highly regulates the expression of the human DEAD-box protein 5 (DDX5), and we define DDX5 as a novel therapeutic target for CRPC treatment. DDX5 overexpression is strongly correlated with aggressive tumor features, notably with CRPC. DDX5 downregulation using a specific ASO-based inhibitor that acts on DDX5 mRNAs inhibits cell proliferation in preclinical models, and it particularly restores the treatment sensitivity of CRPC. Interestingly, through the identification and analysis of DDX5 protein interaction networks, we have identified some specific functions of DDX5 in CRPC that could contribute actively to tumor progression and therapeutic resistance. We first present the interactions of DDX5 and the Ku70/80 heterodimer and the transcription factor IIH, thereby uncovering DDX5 roles in different DNA repair pathways. Collectively, our study highlights critical functions of DDX5 contributing to CRPC progression and provides preclinical proof of concept that a combination of ASO-directed DDX5 inhibition with a DNA damage-inducing therapy can serve as a highly potential novel strategy to treat CRPC.

Splicing factor SRSF3 promotes the progression of cervical cancer through regulating DDX5

Aberrant alternative splicing (AS) profoundly affects tumorigenesis and cancer progression. Serine/arginine-rich splicing factor 3 (SRSF3) regulates the AS of precursor mRNAs and acts as a proto-oncogene in many tumors, but its function and potential mechanisms in cervical cancer remain unclear. Here, we found that SRSF3 was highly expressed in cervical cancer tissues and that SRSF3 expression was correlated with prognosis after analyses of the The Cancer Genome Atlas and GEO databases. Furthermore, knockdown of SRSF3 reduced the proliferation, migration, and invasion abilities of HeLa cells, while overexpression of SRSF3 promoted proliferation, migration, and invasion of CaSki cells. Further studies showed that SRSF3 mediated the variable splicing of exon 12 of the transcriptional cofactor DEAD-box helicase 5 (DDX5). Specifically, overexpression of SRSF3 promoted the production of the pro-oncogenic spliceosome DDX5-L and repressed the production of the repressive spliceosome DDX5-S. Ultimately, both SRSF3 and DDX5-L were able to upregulate oncogenic AKT expression, while DDX5-S downregulated AKT expression. In conclusion, we found that SRSF3 increased the production of DDX5-L and decreased the production of DDX5-S by regulating the variable splicing of DDX5. This, in turn promoted the proliferation, migration, and invasion of cervical cancer by upregulating the expression level of AKT. These results reveal the oncogenic role of SRSF3 in cervical cancer and emphasize the importance of the SRSF3-DDX5-AKT axis in tumorigenesis. SRSF3 and DDX5 are new potential biomarkers and therapeutic targets for cervical cancer.

The RNA helicase DDX5 cooperates with EHMT2 to sustain alveolar rhabdomyosarcoma growth

Rhabdomyosarcoma (RMS) is the most common soft-tissue sarcoma of childhood characterized by the inability to exit the proliferative myoblast-like stage. The alveolar fusion positive subtype (FP-RMS) is the most aggressive and is mainly caused by the expression of PAX3/7-FOXO1 oncoproteins, which are challenging pharmacological targets. Here, we show that the DEAD box RNA helicase 5 (DDX5) is overexpressed in alveolar RMS cells and that its depletion and pharmacological inhibition decrease FP-RMS viability and slow tumor growth in xenograft models. Mechanistically, we provide evidence that DDX5 functions upstream of the EHMT2/AKT survival signaling pathway, by directly interacting with EHMT2 mRNA, modulating its stability and consequent protein expression. We show that EHMT2 in turns regulates PAX3-FOXO1 activity in a methylation-dependent manner, thus sustaining FP-RMS myoblastic state. Together, our findings identify another survival-promoting loop in FP-RMS and highlight DDX5 as a potential therapeutic target to arrest RMS growth.

DEAD-Box RNA Helicases DDX3X and DDX5 as Oncogenes or Oncosuppressors: A Network Perspective

Simple Summary

The transformation of a normal cell into a cancerous one is caused by the deregulation of different metabolic pathways, involving a complex network of protein–protein interactions. The cellular enzymes DDX3X and DDX5 play important roles in the maintenance of normal cell metabolism, but their deregulation can accelerate tumor transformation. Both DDX3X and DDX5 interact with hundreds of different cellular proteins, and depending on the specific pathways in which they are involved, both proteins can either act as suppressors of cancer or as oncogenes. In this review, we summarize the current knowledge about the roles of DDX3X and DDX5 in different tumors. In addition, we present a list of interacting proteins and discuss the possible contribution of some of these protein–protein interactions in determining the roles of DDX3X and DDX5 in the process of cancer proliferation, also suggesting novel hypotheses for future studies.

Abstract

RNA helicases of the DEAD-box family are involved in several metabolic pathways, from transcription and translation to cell proliferation, innate immunity and stress response. Given their multiple roles, it is not surprising that their deregulation or mutation is linked to different pathological conditions, including cancer. However, while in some cases the loss of function of a given DEAD-box helicase promotes tumor transformation, indicating an oncosuppressive role, in other contexts the overexpression of the same enzyme favors cancer progression, thus acting as a typical oncogene. The roles of two well-characterized members of this family, DDX3X and DDX5, as both oncogenes and oncosuppressors have been documented in several cancer types. Understanding the interplay of the different cellular contexts, as defined by the molecular interaction networks of DDX3X and DDX5 in different tumors, with the cancer-specific roles played by these proteins could help to explain their apparently conflicting roles as cancer drivers or suppressors.

Resolution of R-loops by topoisomerase III-β (TOP3B) in coordination with the DEAD-box helicase DDX5

The present study demonstrates how TOP3B is involved in resolving R-loops. We observed elevated R-loops in TOP3B knockout cells (TOP3BKO), which are suppressed by TOP3B transfection. R-loop-inducing agents, the topoisomerase I inhibitor camptothecin, and the splicing inhibitor pladienolide-B also induce higher R-loops in TOP3BKO cells. Camptothecin- and pladienolide-B-induced R-loops are concurrent with the induction of TOP3B cleavage complexes (TOP3Bccs). RNA/DNA hybrid IP-western blotting show that TOP3B is physically associated with R-loops. Biochemical assays using recombinant TOP3B and oligonucleotides mimicking R-loops show that TOP3B cleaves the single-stranded DNA displaced by the R-loop RNA-DNA duplex. IP-mass spectrometry and IP-western experiments reveal that TOP3B interacts with the R-loop helicase DDX5 independently of TDRD3. Finally, we demonstrate that DDX5 and TOP3B are epistatic in resolving R-loops in a pathway parallel with senataxin. We propose a decatenation model for R-loop resolution by TOP3B-DDX5 protecting cells from R-loop-induced damage.

DDX5/METTL3-METTL14/YTHDF2 Axis Regulates Replication of Influenza A Virus

DEAD-box helicase 5 (DDX5), a member of the DEAD/H-box helicases, is known to participate in all aspects of RNA metabolism. However, its regulatory effect in antiviral innate immunity during replication of influenza virus remains unclear. Herein, we found that human DDX5 promotes replication of influenza virus in A549 cells. Moreover, our results further revealed that DDX5 relies on its N terminus to interact with the nucleoprotein (NP) of influenza virus, which is independent of RNA. Of course, we also observed colocalization of DDX5 with NP in the context of transfection or infection. However, influenza virus infection had no significant effect on the protein expression and nucleocytoplasmic distribution of DDX5. Importantly, we found that DDX5 suppresses antiviral innate immunity induced by influenza virus infection. Mechanistically, DDX5 downregulated the mRNA levels of interferon beta (IFN-β), interleukin 6 (IL-6), and DHX58 via the METTL3-METTL14/YTHDF2 axis. We revealed that DDX5 bound antiviral transcripts and regulated immune responses through YTHDF2-dependent mRNA decay. Taken together, our data demonstrate that the DDX5/METTL3-METTL14/YTHDF2 axis regulates the replication of influenza A virus. IMPORTANCE The replication and transcription of influenza virus depends on the participation of many host factors in cells. Exploring the relationship between viruses and host factors will help us fully understand the characteristics and pathogenic mechanisms of influenza viruses. In this study, we showed that DDX5 interacted with the NP of influenza virus. We demonstrated that DDX5 downregulated the expression of IFN-β and IL-6 and the transcription of antiviral genes downstream from IFN-β in influenza virus-infected A549 cells. Additionally, DDX5 downregulated the mRNA levels of antiviral transcripts via the METTL3-METTL14/YTHDF2 axis. Our findings provide a novel perspective to understand the mechanism by which DDX5 regulates antiviral immunity.

Circular RNA dehydrodolichyl diphosphate synthase facilitated triple-negative breast cancer progression via miR-362-3p/DDX5 axis

BACKGROUND

Triple-negative breast cancer (TNBC) is a common hypotype of breast cancer. Circular RNAs (circRNAs) are burgeoning serve as vital controllers in numerous tumors. Nevertheless, the expression and regulatory mode of circRNAs in TNBC are still indistinct. This paper aimed to reveal the function and molecular mechanism of circular RNA dehydrodolichyl diphosphate synthase (circDHDDS) in TNBC.

METHODS

The contents of circDHDDS, DHDDS mRNA, microRNA-362-3p (miR-362-3p) and DEAD (Asp-Glu-Ala-Asp) box polypeptide 5 (DDX5) were indicated by quantitative real-time polymerase chain reaction (qRT-PCR) and western blot. The colony formation assay and 5-ethynyl-2'-deoxyuridine (EdU) assay were executed to assess cell proliferation. The flow cytometry assay was utilized to detect cell apoptosis. The transwell assay and tube formation assay were applied to measure cell migration, invasion and angiogenesis. The targeted relationships of miR-362-3p and circDHDDS or DDX5 were forecasted and detected by dual-luciferase reporter assay. The in vivo test was implemented to confirm the effect of circDHDDS.

RESULTS

The contents of circDHDDS and DDX5 were increased, and miR-362-3p level was decreased in TNBC. CircDHDDS deficiency reserved cell proliferation, migration, invasion and angiogenesis, while facilitated cell apoptosis in TNBC cells. Furthermore, miR-362-3p was validated to exert a tumor repressive effect in TNBC cells by suppressing DDX5. Moreover, DDX5 could regulate the development of TNBC. The experimental data exposed that levels of miR-362-3p presented noteworthy negative correlation with circDHDDS and DDX5, while circDHDDS and DDX5 exhibited significant positive correlation. In mechanism, circDHDDS bound to miR-362-3p to modulate DDX5 expression. In addition, circDHDDS knock-down also attenuated tumor growth.

CONCLUSION

CircDHDDS expedited TNBC by swelling DDX5 via adapting miR-362-3p.

Circular RNA PUM1 performs as a competing endogenous RNA of microRNA-340-5p to mediate DEAD-box helicase 5 to mitigate cerebral ischemia-reperfusion injury

Cerebral ischemia-reperfusion damages local brain tissue and impairs brain function, but its specific pathogenesis is still uncertain. Recent studies have clarified circPUM1 is aberrantly elevated in cerebral ischemia-reperfusion injury; however, circPUM1ʹs function in cerebral ischemia-reperfusion-induced neuronal injury remains ambiguous. The results illustrated circPUM1 and DEAD-box helicase 5 were decreased, but microRNA-340-5p was elevated in transient middle cerebral artery occlusion mice and oxygen glucose deprivation/reoxygenation-treated SH-SY5Y cells. Knockdown of circPUM1 aggravated the neuronal injury in transient middle cerebral artery occlusion mice and motivated glial cell activation, neuronal apoptosis and inflammation. Enhancing circPUM1 restrained oxygen glucose deprivation/reoxygenation-induced SH-SY5Y cell apoptosis, the release of lactate dehydrogenase and inflammatory factors, and activation of nuclear factor-kappaB pathway, while elevating microRNA-340-5p aggravated oxygen glucose deprivation/reoxygenation-induced cell damage. Functional rescue experiments exhibited that the impacts of knockdown or enhancement of circPUM1 were turned around by microRNA-340-5p downregulation and DEAD-box helicase 5 silencing, respectively. Moreover, it was demonstrated that circPUM1 competitively adsorbed microRNA-340-5p to mediate DEAD-box helicase 5. All in all, this study clarifies that circPUM1 mitigates cerebral ischemia-reperfusion-induced neuronal injury by targeting the microRNA-340-5p/DEAD-box helicase 5 axis.

The RNA helicases DDX5 and DDX17 facilitate neural differentiation of human pluripotent stem cells NTERA2

AIMS

Understanding human neurogenesis is critical toward regenerative medicine for neurodegeneration. However, little is known how neural differentiation is regulated by DEAD box-containing RNA helicases, which comprise a diverse class of RNA remodeling enzymes.

MATERIALS AND METHODS

ChIP-seq was utilized to identify binding sites of DDX5 and DDX17 in both human pluripotent stem cell (hPSC) line NTERA2 and their retinoic acid-induced neural derivatives. RNA-seq was used to elucidate genes differentially expressed upon depletion of DDX5 and DDX17. Neurosphere assay, flow cytometry, and immunofluorescence staining were performed to test the effect of depletion of the two RNA helicases in neural differentiation.

KEY FINDINGS

We show here that expression of DDX5 and DDX17 is abundant throughout neural differentiation of NTERA2, and is mostly localized within the nucleus. The two RNA helicases occupy chromatin genome-wide at regions associated with neurogenesis-related genes in both hPSCs and their neural derivatives. Further, both DDX5 and DDX17 are mutually required for controlling transcriptional expression of these genes, but are not important for maintenance of stem cell state of hPSCs. In contrast, they facilitate early neural differentiation of hPSCs, generation of neurospheres from the stem cells, and transcriptional expression of key neurogenic transcription factors such as SOX1 and PAX6 during neural differentiation. Importantly, DDX5 and DDX17 are critical for differentiation of hPSCs toward NESTIN- and TUBB3-positive cells, which represent neural progenitors and mature neurons, respectively.

SIGNIFICANCE

Collectively, our findings suggest the role of DDX5 and DDX17 in transcriptional regulation of genes involved in neurogenesis, and hence in neural differentiation of hPSCs.

PAK5 promotes RNA helicase DDX5 sumoylation and miRNA-10b processing in a kinase-dependent manner in breast cancer

P21-activated kinase 5 (PAK5) plays an important role in tumors. However, the functional role of PAK5 in mammary tumorigenesis in vivo remains unclear. Here, we show that PAK5 deficiency represses MMTV-PyVT-driven breast tumorigenesis. DEAD-box RNA helicase 5 (DDX5) is a substrate of PAK5, which is phosphorylated on threonine 69. PAK5-mediated DDX5 phosphorylation promotes breast cancer cell proliferation and metastasis. The increased expression levels of PAK5 and phospho-DDX5 threonine 69 are associated with metastasis and poor clinical outcomes of patients. PAK5 facilitates the phosphorylation-dependent sumoylation of DDX5 to stabilize DDX5. Both the phosphorylation and sumoylation of DDX5 enhance the formation of a DDX5/Drosha/DGCR8 complex, thus promoting microRNA-10b processing. Finally, we verify decreased expression of DDX5 phosphorylation and sumoylation and mature miR-10b in PAK5^-/-/MMTV-PyVT transgenic mice. Our findings provide insights into the function of PAK5 in microRNA (miRNA) biogenesis, which might be a potential therapeutic target for breast cancer.

Upregulated expression of DDX5 predicts recurrence and poor prognosis in breast cancer

DEAD-box helicase 5 (DDX5) has been shown to promote tumorigenesis and cancer progression. However, the relationship between DDX5 and recurrence in breast cancer (BC) patients remains unknown. The objective of the present study was to evaluate the correlation of DDX5 with recurrence-free survival (RFS) and breast cancer-specific survival (BCSS) in patients with BC. The expression of DDX5 was examined by immunohistochemical analysis. RFS was calculated by Kaplan-Meier survival analysis. Univariate and multivariable associations were assessed by Cox proportional hazards models. In the present study, a total of 868 BC patients were analysed, and we found that DDX5 protein was significantly overexpressed in BC tissues compared to adjacent normal tissues. Elevated DDX5 was associated with an aggressive phenotype in BC patients. Moreover, DDX5 protein was upregulated in recurrent patients compared with nonrecurrent patients, and DDX5 protein levels were positively associated with worse RFS and BCSS in BC patients. High DDX5 expressing BC patients with age more than 50 year, advanced clinical stage or histological grade had a significantly increased risk of recurrence and shorter survival. Our findings highlight the significance of DDX5 in the recurrence and clinical outcome of BC patients and suggest that DDX5 may be a potential predictive biomarker for patients with BC.

LncPSCA in the 8q24.3 risk locus drives gastric cancer through destabilizing DDX5

Genome-wide association studies (GWAS) have identified multiple gastric cancer risk loci and several protein-coding susceptibility genes. However, the role of long-noncoding RNAs (lncRNAs) transcribed from these risk loci in gastric cancer development and progression remains to be explored. Here, we functionally characterize a lncRNA, lncPSCA, as a novel tumor suppressor whose expression is fine-regulated by a gastric cancer risk-associated genetic variant. The rs2978980 T > G change in an intronic enhancer of lncPSCA interrupts binding of transcription factor RORA, which down-regulates lncPSCA expression in an allele-specific manner. LncPSCA interacts with DDX5 and promotes DDX5 degradation through ubiquitination. Increased expression of lncPSCA results in low levels of DDX5, less RNA polymerase II (Pol II) binding with DDX5 in the nucleus, thus activating transcription of multiple p53 signaling genes by Pol II. These findings highlight the importance of functionally annotating lncRNAs in GWAS risk loci and the great potential of modulating lncRNAs as innovative cancer therapy.

Multiple functions of the DEAD-box RNA helicase, DDX5 (p68), make DDX5 a superior oncogenic biomarker and target for targeted cancer therapy

DDX5 (p68) is a well-known multifunctional DEAD-box RNA helicase and a transcription cofactor. Since its initial discovery more than three decades ago, DDX5 is gradually recognized as a potential biomarker and target for the treatment of various cancer types. Studies over the years significantly expanded our understanding of the functional diversity of DDX5 in various cancer types and extended our knowledge of its Mechanism of Action (MOA). This provides a rationale for the development of novel cancer therapeutics by using DDX5 as a biomarker and a therapeutic target. However, while most of the published studies have found DDX5 to be an oncogenic target and a cancer treatment-resistant biomarker, a few studies have reported that in certain scenarios, DDX5 may act as a tumor suppressor. After careful review of all the available relevant studies in the literature, we found that the multiple functions of DDX5 make it both a superior independent oncogenic biomarker and target for targeted cancer therapy. In this article, we will summarize the relevant studies on DDX5 in literature with a careful analysis and discussion of any inconsistencies encountered, and then provide our conclusions with respect to understanding the MOA of FL118, a novel small molecule. We hope that such a review will stimulate further discussion on this topic and assist in developing better strategies to treat cancer by using DDX5 as both an oncogenic biomarker and therapeutic target.

PUM1 Is Overexpressed in Colon Cancer Cells With Acquired Resistance to Cetuximab

Background

Cetuximab is an effective antibody to treat colorectal cancer (CRC) by targeting the epidermal growth factor receptor (EGFR). However, the mechanisms of acquired resistance to cetuximab therapy, especially in patients without identifiable gene mutations, are not fully understood.

Methods

Our study investigated the role of pumilio RNA-binding family member 1 (PUM1) in cetuximab resistance. We established cetuximab-resistant colon cancer cell lines SW480R and Caco-2R and knocked out PUM1 and DEAD-box helicase 5 (DDX5) with the clustered regularly interspaced short palindromic repeats (CRISPR)-caspase 9 (Cas9) system. To check cell proliferation, we used Cell Counting Kit-8. We performed qPCR and immunoblot to examine the levels of mRNAs and proteins for each cell line.

Results

Our data showed that PUM1 was upregulated in SW480R and Caco-2R cells with increased protein levels and cell proliferation, and PUM1 knockout reduced cell viability in the presence of cetuximab. We also found that PUM1 interacted with DDX5 in 3′ untranslated region (UTR) and positively regulated its mRNA expression. Furthermore, suppression of DDX5 also decreased the proliferation of SW480R and Caco-2R cells.

Conclusion

Our study suggests that PUM1 positively regulates DDX5 and acts as a promoter in cetuximab-resistant colon cancer cells.

DEAD-Box RNA Helicases in Cell Cycle Control and Clinical Therapy

Cell cycle is regulated through numerous signaling pathways that determine whether cells will proliferate, remain quiescent, arrest, or undergo apoptosis. Abnormal cell cycle regulation has been linked to many diseases. Thus, there is an urgent need to understand the diverse molecular mechanisms of how the cell cycle is controlled. RNA helicases constitute a large family of proteins with functions in all aspects of RNA metabolism, including unwinding or annealing of RNA molecules to regulate pre-mRNA, rRNA and miRNA processing, clamping protein complexes on RNA, or remodeling ribonucleoprotein complexes, to regulate gene expression. RNA helicases also regulate the activity of specific proteins through direct interaction. Abnormal expression of RNA helicases has been associated with different diseases, including cancer, neurological disorders, aging, and autosomal dominant polycystic kidney disease (ADPKD) via regulation of a diverse range of cellular processes such as cell proliferation, cell cycle arrest, and apoptosis. Recent studies showed that RNA helicases participate in the regulation of the cell cycle progression at each cell cycle phase, including G1-S transition, S phase, G2-M transition, mitosis, and cytokinesis. In this review, we discuss the essential roles and mechanisms of RNA helicases in the regulation of the cell cycle at different phases. For that, RNA helicases provide a rich source of targets for the development of therapeutic or prophylactic drugs. We also discuss the different targeting strategies against RNA helicases, the different types of compounds explored, the proposed inhibitory mechanisms of the compounds on specific RNA helicases, and the therapeutic potential of these compounds in the treatment of various disorders.

LncRNA SNHG14 promotes cell proliferation and invasion in colorectal cancer through modulating miR-519b-3p/DDX5 axis

Numbers of studies suggest that long non-coding RNAs (lncRNAs) exert an important role in cancer progression. It is reported that lncRNA SNHG14 (SNHG14) promotes cell proliferation and invasion in many cancers. However, the underlying molecular mechanism of SNHG14 in colorectal cancer (CRC) remains unclear. In our study, we found that SNHG14 is highly expressed in CRC tissues and cells, especially in SW480 and HT-29 cells. In addition, sh-SNHG14 inhibits cell proliferation, cell migration and invasion, promotes cell apoptosis in CRC cell lines. Furthermore, we found that SNHG14 functions as a sponge for miR-519b-3p, while the DEAD box protein 5 (DDX5) is a downstream target gene of miR-519b-3p, and the functions of miR-519b-3p inhibitors on the CRC progression could be rescued by downregulation of DDX5. Our findings suggest that SNHG14 promotes the CRC progression by miR-519b-3p/DDX5 axis, implying the promising therapeutic target of SNHG4 for CRC patients.

RNA helicase DDX5 acts as a critical regulator for survival of neonatal mouse gonocytes

OBJECTIVES

Mammalian spermatogenesis is a biological process of male gamete formation. Gonocytes are the only precursors of spermatogonial stem cells (SSCs) which develop into mature spermatozoa. DDX5 is one of DEAD-box RNA helicases and expresses in male germ cells, suggesting that Ddx5 plays important functions during spermatogenesis. Here, we explore the functions of Ddx5 in regulating the specification of gonocytes.

MATERIALS AND METHODS

Germ cell-specific Ddx5 knockout (Ddx5-/- ) mice were generated. The morphology of testes and epididymides and fertility in both wild-type and Ddx5-/- mice were analysed. Single-cell RNA sequencing (scRNA-seq) was used to profile the transcriptome in testes from wild-type and Ddx5-/- mice at postnatal day (P) 2. Dysregulated genes were validated by single-cell qRT-PCR and immunofluorescent staining.

RESULTS

In male mice, Ddx5 was expressed in germ cells at different stages of development. Germ cell-specific Ddx5 knockout adult male mice were sterile due to completely devoid of germ cells. Male germ cells gradually disappeared in Ddx5-/- mice from E18.5 to P6. Single-cell transcriptome analysis showed that genes involved in cell cycle and glial cell line-derived neurotrophic factor (GDNF) pathway were significantly decreased in Ddx5-deficient gonocytes. Notably, Ddx5 ablation impeded the proliferation of gonocytes.

CONCLUSIONS

Our study reveals the critical roles of Ddx5 in fate determination of gonocytes, offering a novel insight into the pathogenesis of male sterility.

LINC01207 is up-regulated in gastric cancer tissues and promotes disease progression by regulating miR-671-5p/DDX5 axis

LINC01207 is involved in the progression of some cancers. This study was designed to delve into the biological function and mechanism of LINC01207 in gastric cancer. qPCR was adopted to examine the expression levels of LINC01207, miR-671-5p, DDX5 mRNA in gastric cancer tissues and cells. After LINC01207 was overexpressed or depleted, MTT and BrdU assays were conducted to detect cell proliferation. Transwell assay was employed to detect cell migration and invasion. Western blot was used to detect the expression of DDX5 protein in cells. Bioinformatics analysis, luciferase reporter assay and RNA pull-down assay were performed to predict and validate the binding site between miR-671-5p and LINC01207 or DDX5. LINC01207, DDX5 mRNA were up-regulated in gastric cancer, while miR-671-5p was down-regulated; high expression of LINC01207 and transfection of miR-671-5p inhibitors facilitated the proliferation of gastric cancer cells; however, knocking down LINC01207 and the overexpression of miR-671-5p mimics had opposite biological effects. LINC01207 and miR-671-5p were interacted and miR-671-5p was negatively regulated by LINC01207. MiR-671-5p could reverse the function of LINC01207. DDX5 was a downstream target of miR-671-5p and was positively modulated by LINC01207. LINC01207 promotes the proliferation and metastasis of gastric cancer cells by regulating miR-671-5p/DDX5 axis.

A new interaction between BRCA2 and DDX5 promotes the repair of DNA breaks at transcribed chromatin

In a recent report, we have revealed a new interaction between the BRCA2 DNA repair associated protein (BRCA2) and the DEAD-box helicase 5 (DDX5) at DNA breaks that promotes unwinding DNA-RNA hybrids within transcribed chromatin and favors repair. Interestingly, BRCA2-DDX5 interaction is impaired in cells expressing the BRCA2^{T2 07A} missense variant found in breast cancer patients.

MSC-AS1 induced cell growth and inflammatory mediators secretion through sponging miR-142-5p/DDX5 in gastric carcinoma

Emerging studies have noted that dysregulated lncRNAs are implicated in cancer progression and tumorigenesis. We first showed that MSC-AS1 was overexpressed in gastric cancer (GC) cells (HGC-27, MKN-45, SGC-7901 and MGC-803 cells) compared with GES cells. We observed that MSC-AS1 was upregulated in GC specimens compared with paired normal specimens. MSC-AS1 increased cell growth and cycle progression. Moreover, the overexpression of MSC-AS1 enhanced the secretion of the inflammatory mediators IL-1β, IL-6 and TNF-α. We found that the overexpression of MSC-AS1 inhibited the expression of miR-142-5p in HGC-27 cells. We noted that DDK5 was a target gene of miR-142-5p. The overexpression of miR-142-5p suppressed the luciferase activity of wild-type DDX5, but the luciferase activity of the mutant DDX5 was not changed. We showed that miR-142-5p was downregulated in GC specimens compared with paired normal specimens. MSC-AS1 expression was inversely correlated with miR-142-5p expression in GC specimens. MSC-AS1 induced cell growth, cell cycle progression and inflammatory mediator secretion by modulating DDX5. These results showed that MSC-AS1 functions as a key oncogene in the development of GC.

Cerebral Cavernous Malformation 1 Determines YAP/TAZ Signaling-Dependent Metastatic Hallmarks of Prostate Cancer Cells

Enhanced Yes-associated protein (YAP)/transcriptional co-activator with PDZ-binding motif (TAZ) signaling is correlated with the extraprostatic extension of prostate cancer. However, the mechanism by which YAP/TAZ signaling becomes hyperactive and drives prostate cancer progression is currently unclear. In this study, we revealed that higher expression of CCM1, which is uniquely found in advanced prostate cancer, is inversely correlated with metastasis-free and overall survival in patients with prostate cancer. We also demonstrated that CCM1 induces the metastasis of multiple types of prostate cancer cells by regulating YAP/TAZ signaling. Mechanistically, CCM1, a gene mutated in cerebral cavernous malformation, suppresses DDX5, which regulates the suppression of YAP/TAZ signaling, indicating that CCM1 and DDX5 are novel upstream regulators of YAP/TAZ signaling. Our findings highlight the importance of CCM1-DDX5-YAP/TAZ signaling in the metastasis of prostate cancer cells.

Long Non-Coding RNA RMRP Contributes to Sepsis-Induced Acute Kidney Injury

PURPOSE

This study aimed to explore the role of the long non-coding RNA (lncRNA) RNA component of mitochondrial RNAase P (RMRP) in sepsis-induced acute kidney injury (AKI).

MATERIALS AND METHODS

Venous blood was collected from septic patients and healthy people. C57BL/6 mice who underwent cecal ligation and puncture (CLP) were used as in vivo models of septic AKI. Lipopolysaccharide (LPS)-induced HK-2 cells were employed as in vitro models of AKI. Flow cytometry analysis was conducted to detect cell apoptosis. Enzyme-linked immunosorbent assay and Western blot assays were used to detect levels of pro-inflammatory cytokines.

RESULTS

RMRP was upregulated in sera from patients with AKI and in LPS-induced cells. Knockdown of RMRP inhibited cell apoptosis and reduced production of inflammatory factors in LPS-induced cells, as well as alleviated AKI in CLP mice. RMRP facilitated inflammation by activating NACHT, LRR, and PYD domains-containing protein 3 (NLRP3) inflammasome. We found that microRNA 206 (miR-206) binds with and is negatively regulated by RMRP: miR-206 directly targets the 3' untranslated region of DEAD-box helicase 5 (DDX5) and negatively regulates DDX5 expression. By binding with miR-206, RMRP upregulated DDX5 expression. Rescue assays revealed that overexpression of DDX5 counteracted the effect of RMRP inhibition on cell apoptosis and inflammatory response in LPS-induced cells.

CONCLUSION

The lncRNA RMRP contributes to sepsis-induced AKI through upregulation of DDX5 in a miR-206 dependent manner and through activation of NLRP3 inflammasome. This novel discovery may provide a potential strategy for treating AKI.

Silencing of Long Non-Coding RNA FGD5-AS1 Inhibits the Progression of Non-Small Cell Lung Cancer by Regulating the miR-493-5p/DDX5 Axis

Background:

Long non-coding RNA FGD5 antisense RNA 1 (FGD5-AS1), identified to be a carcinogenic lncRNA, exhibits a regulatory role in some malignancies including non-small cell lung cancer (NSCLC). The aim of the present research is to decipher the function and underlying mechanism of FGD5-AS1 in progression of NSCLC.

Methods:

Expression of FGD5-AS1, miR-493-5p and DEAD-box protein 5 (DDX5) in NSCLC tissues and cells was quantified utilizing qRT-PCR. Cell proliferation was assessed by CCK-8 method. Scratch healing test and Transwell assay were used for assaying cell migration and invasion. Expressions of DDX5 and epithelial-mesenchymal transition (EMT)-related proteins were examined by Western blot. Additionally, targeting relationships between FGD5-AS1 and miR-493-5p, miR-493-5p and DDX5 were verified by dual-luciferase reporter gene assay.

Results:

Expression of FGD5-AS1 in NSCLC tissues and cell lines was up-regulated. Expression of FGD5-AS1 was in association with enlarged tumor size and lymph node metastasis of the patients. Knockdown of FGD5-AS1 led to the inhibition of proliferation, migration, invasion and EMT of NSCLC cells. FGD5-AS1 directly targeted miR-493-5p, while DDX5 was the target of miR-493-5p in NSCLC cells. Additionally, FGD5-AS1 could positively regulate the expression of DDX5 via suppressing miR-493-5p.

Conclusion:

FGD5-AS1 facilitates the proliferation, migration, invasion and EMT of NSCLC cells by sponging miR-493-5p and up-regulating DDX5.

Simvastatin suppresses renal cell carcinoma cells by regulating DDX5/DUSP5

OBJECTIVES

Renal cell carcinoma (RCC) has the highest mortality rate of genitourinary cancers and the incidence of RCC has risen steadily. Simvastatin has been reported to exhibit anti-tumor activity in a variety of cancers; however, its roles and molecular mechanisms in RCC remain unclear. Our aim was to evaluate the inhibitory effect of simvastatin on RCC.

METHODS

We used a variety of methods to test the changes of RCC cell lines' viability, migration, invasion, cell cycle and apoptosis after treatment with simvastatin.

RESULTS

We found that simvastatin not only inhibited RCC cell viability, migration, and invasion, but also regulated the cell cycle and induced apoptosis. We also observed abnormal expression of DDX5 and DUSP5 in RCC cell lines. Mechanistic investigation showed that simvastatin significantly suppressed DDX5 and promoted DUSP5 expression.

CONCLUSION

Together, these results provide a novel mechanism underlying simvastatin-induced inhibition of RCC via regulation of the DDX5/DUSP5 axis.

Endoxifen and fulvestrant regulate estrogen-receptor α and related DEADbox proteins

Breast cancer (BC) represents the most common type of cancer in females worldwide. Endocrine therapy evolved as one of the main concepts in treatment of hormone-receptor positive BC. Current research focuses on the elucidation of tumour resistance mechanisms against endocrine therapy. In a translational in vitro approach, potential regulatory effects of clinically implemented BC anti-oestrogens on ERα, its coactivators DDX5, DDX17 and other DEADbox proteins as well as on the proliferation markers cyclin D1 and Ki67 were investigated on both the RNA and protein level. BC in vitro models for hormone-receptor positive (MCF-7, T-47D) and hormone-receptor negative cells (BT-20) were subjected to endocrine therapy. Anti-oestrogen-dependent expression regulation of target genes on the transcriptional and translational level was quantified and statistically assessed. Endocrine therapy decreases the expression levels of Ki67, cyclin D1 and ERα in hormone-receptor positive cells. In the hormone-receptor negative cells, the three parameters remained stable after endocrine therapy. Endoxifen triggers a downregulation of DDX5 and DDX23 in MCF-7 cells. Fulvestrant treatment downregulates the expression levels of all investigated DEADbox proteins in MCF-7 cells. In T-47D cells, endoxifen and fulvestrant lead to a decrease of all target gene expression levels. Interestingly, endocrine therapy affects DEADbox RNA expression levels in BT-20 cells, too. However, this result could only be confirmed for DDX1, immunocytologically. The investigated DEADbox proteins appear to correlate with the oestrogen-dependent tumourigenesis in hormone-receptor positive BC and show expression alterations after endocrine treatment.

Decreased expression of DEAD-Box helicase 5 inhibits esophageal squamous cell carcinomas by regulating endoplasmic reticulum stress and autophagy

DEAD-Box Helicase 5(DDX5), also known as P68, is one of the founding members of the DEAD-Box helicase superfamily and it plays a key role in RNA metabolism. Several studies have reported that DDX5 is involved in many types of tumors through abnormal expression, but the detailed mechanism of DDX5 in esophageal squamous cell carcinoma (ESCC) has not been elucidated. In this study, we demonstrate that the level of DDX5 is a negative prognostic factor for ESCC. The obtained results indicated that decreased expression of DDX5 inhibits ESCC cell proliferation and metastasis. Further experiments suggested that CDK2, Cyclin D1 and Vimentin were downregulated, while E-cadherin was upregulated after DDX5 was knocked down. In addition, DDX5 was positively correlated with the expression of BIP, phospho-eIF2α, phospho-PERK and P62, suggesting that knockdown of DDX5 can inhibit endoplasmic reticulum(ER) stress and promote the recovery of autophagy flux. Therefore, this study demonstrates that the downregulation of DDX5 in ESSC correlates to lower malignancy and presents a novel target for the development of new treatment strategies.

Translational Repression of G3BP in Cancer and Germ Cells Suppresses Stress Granules and Enhances Stress Tolerance

Stress granules (SGs) are membrane-less ribonucleoprotein condensates that form in response to various stress stimuli via phase separation. SGs act as a protective mechanism to cope with acute stress, but persistent SGs have cytotoxic effects that are associated with several age-related diseases. Here, we demonstrate that the testis-specific protein, MAGE-B2, increases cellular stress tolerance by suppressing SG formation through translational inhibition of the key SG nucleator G3BP. MAGE-B2 reduces G3BP protein levels below the critical concentration for phase separation and suppresses SG initiation. Knockout of the MAGE-B2 mouse ortholog or overexpression of G3BP1 confers hypersensitivity of the male germline to heat stress in vivo. Thus, MAGE-B2 provides cytoprotection to maintain mammalian spermatogenesis, a highly thermosensitive process that must be preserved throughout reproductive life. These results demonstrate a mechanism that allows for tissue-specific resistance against stress and could aid in the development of male fertility therapies.

Linc00473 potentiates cholangiocarcinoma progression by modulation of DDX5 expression via miR-506 regulation

Background

Cholangiocarcinoma (CCA) is a mortal cancer with high mortality, whereas the function and mechanism of occurrence and progression of CCA are still mysterious. Long non-coding RNAs (lncRNAs) could function as important regulators in carcinogenesis and cancer progression. Growing evidences have indicated that the novel lncRNA linc00473 plays an important role in cancer progression and metastasis. However, its function and molecular mechanism in CCA remain unknown.

Methods

The linc00473 expression in CCA tissues and cell lines was analyzed using qRT-PCR. Gain- and loss-of-function experiments were conducted to investigate the biological functions of linc00473 both in vitro and in vivo. Insights into the underlying mechanisms of competitive endogenous RNAs (ceRNAs) were determined by bioinformatics analysis, dual-luciferase reporter assays, qRT-PCR arrays, RNA immunoprecipitation (RIP) and rescue experiments.

Results

Linc00473 was highly expressed in CCA tissues and cell lines. Linc00473 knockdown inhibited CCA growth and metastasis. Furthermore, linc00473 acted as miR-506 sponge and regulated its target gene DDX5 expression. Rescue assays verified that linc00473 modulated the tumorigenesis of CCA by regulating miR-506.

Conclusions

The data indicated that linc00473 played an oncogenic role in CCA growth and metastasis, and could serve as a novel molecular target for treating CCA.

Camptothecin induced DDX5 degradation increased the camptothecin resistance of osteosarcoma

Osteosarcoma (OS) is the most common primary malignant bone tumor in children and adolescents. Unfortunately, chemo-resistance is a huge obstacle in the treatment of OS. However, the underlying molecular mechanisms of OS chemo-resistance still remain unknown. Here we reported that the resistance to camptothecin (cpt) therapy was driven by degradation of DDX5. DDX5 knockdown decreased cell death and DNA damage and recovered cell proliferation in cpt treated 143B cells. Furthermore, we found that DDX5 bound to NONO, a kind of DNA repairing protein, and regulated NONO functions. Our data verified that cpt-induced degradation of DDX5 following by breaking down the protein bound of NONO, which participated in the resistance of cpt. In the summary, according to our results, DDX5 might be a potential therapeutic target for improving clinical outcomes of cpt in OS.

DDX5 Silencing Suppresses the Migration of Basal cell Carcinoma Cells by Downregulating JAK2/STAT3 Pathway

Basal cell carcinoma is driven by the aberrant activation of hedgehog signaling. DEAD (Asp-Glu-Ala-Asp) box protein 5 is frequently overexpressed in human cancer cells and associated with the tumor growth and invasion. The purpose of this study was to investigate the role of DEAD (Asp-Glu-Ala-Asp) box protein 5 in the growth, migration, and invasion of basal cell carcinoma. The role of DEAD (Asp-Glu-Ala-Asp) box protein 5 was detected by quantitative real-time polymerase chain reaction, Western blot, and terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling assay in basal cell carcinoma cells. The associations between JAK2/STAT3 pathway and DEAD (Asp-Glu-Ala-Asp) box protein 5 were analyzed in basal cell carcinoma cells. Results showed that DEAD (Asp-Glu-Ala-Asp) box protein 5 is overexpressed in basal cell carcinoma cells. DEAD (Asp-Glu-Ala-Asp) box protein 5 knockdown inhibited the migration and invasion of basal cell carcinoma cells. DEAD (Asp-Glu-Ala-Asp) box protein 5 knockdown increased the apoptosis of basal cell carcinoma cells induced by tunicamycin. Results found that DEAD (Asp-Glu-Ala-Asp) box protein 5 knockdown increased JAK2 and STAT3 expression in basal cell carcinoma cells. JAK2 inhibitor decreased STAT3 expression and abolished the inhibitory effects of DEAD (Asp-Glu-Ala-Asp) box protein 5 silencing on migration and invasion in basal cell carcinoma cells. In conclusion, these results indicate that DEAD (Asp-Glu-Ala-Asp) box protein 5 is a potential target for inhibiting basal cell carcinoma cells growth, migration, and invasion by downregulating JAK2/STAT3 pathway.

DDX5 potentiates HIV-1 transcription as a co-factor of Tat

BACKGROUND

HIV-1 does not encode a helicase and hijacks those of the cell for efficient replication. We and others previously showed that the DEAD box helicase, DDX5, is an essential HIV dependency factor. DDX5 was recently shown to be associated with the 7SK snRNP. Cellular positive transcription elongation factor b (P-TEFb) is bound in an inactive form with HEXIM1/2 on 7SK snRNP. The Tat/P-TEFb complex is essential for efficient processivity of Pol II in HIV-1 transcription elongation and Tat competes with HEXIM1/2 for P-TEFb. We investigated the precise role of DDX5 in HIV replication using siRNA mediated knockdown and rescue with DDX5 mutants which prevent protein-protein interactions and RNA and ATP binding.

RESULTS

We demonstrate a critical role for DDX5 in the Tat/HEXIM1 interaction. DDX5 acts to potentiate Tat activity and can bind both Tat and HEXIM1 suggesting it may facilitate the dissociation of HEXIM1/2 from the 7SK-snRNP complex, enhancing Tat/P-TEFb availability. We show knockdown of DDX5 in a T cell line significantly reduces HIV-1 infectivity and viral protein production. This activity is unique to DDX5 and cannot be substituted by its close paralog DDX17. Overexpression of DDX5 stimulates the Tat/LTR promoter but suppresses other cellular and viral promoters. Individual mutations of conserved ATP binding, RNA binding, helicase related or protein binding motifs within DDX5 show that the N terminal RNA binding motifs, the Walker B and the glycine doublet motifs are essential for this function. The Walker A and RNA binding motifs situated on the transactivation domain are however dispensable.

CONCLUSION

DDX5 is an essential cellular factor for efficient HIV transcription elongation. It interacts with Tat and may potentiate the availability of P-TEFb through sequestering HEXIM1.

Induction of DEAD Box helicase 5 in early adipogenesis is regulated by Ten-eleven translocation 2

Dead box helicase 5 (DDX5) is an RNA helicase that is has cellular function on RNA splicing and transcriptional regulation. It has been reported to be involved in cell differentiation including adipogenesis. However, it is not clear how DDX5 is regulated during adipogenesis. Our previous report demonstrated that the Ten-eleven translocation methyl-cytosine dioxygenase 2 (TET2) is required for adipogenesis. This study was aimed to investigate DDX5 as a direct target of TET2 upon adipogenic induction of 3T3-L1 preadipocyte. Microarray-based screening of differentially expressed genes upon TET2 knockdown identified genes involved in cell cycle, DNA replication, and ribosome biology as major targets of TET2 in the initial step of adipogenic induction. The Ddx5 gene was identified and validated as the target. TET2-mediated epigenetic regulation of the Ddx5 gene was measured by two independent methods including immunoprecipitation against 5-hydroxymethylcytosine (5hmC) and 5-methylcytosine (5mC) as well as EpiMark 5hmC and 5mC analysis. Ddx5 expression was downregulated upon TET2 knockdown, coincided with a significant decrease of 5hmC at the Ddx5 locus. DDX5 knockdown significantly suppressed adipogenesis, while DDX5 overexpression promoted it. Importantly, DDX5 overexpression, when co-transfected, rescued the process of adipogenesis, which was hindered by TET2 siRNA treatment. The findings suggest TET2-mediated regulation of the Ddx5 gene is required for an initial step of adipogenesis.

Silencing of p68 and STAT3 synergistically diminishes cancer progression

AIMS

Since several factors are involved in the tumorigenesis process, targeting only one factor most probably cannot overwhelm cancer progression. Therefore, it seems that combination therapy through targeting more than one cancer-related factor may lead to cancer control. The expression and function of p68 (DDX5; DEAD-Box Helicase 5) are dysregulated in various cancers. P68 is also a co-activator of many oncogenic transcription factors such as the signal transducer and activator of transcription-3 (STAT3), which contributes to cancer progression. This close connection between p68 and STAT3 plays an important role in the growth and development of cancer.

MATERIALS AND METHODS

We decided to suppress the p68/STAT3 axis in various cancer cells by using Polyethylene glycol-trimethyl Chitosan-Hyaluronic acid (PEG-TMC-HA) nanoparticles (NPs) loaded with siRNA molecules. We assessed the impact of this combination therapy on apoptosis, proliferation, angiogenesis, and tumor growth, both in vitro and in vivo.

KEY FINDINGS

The results showed that siRNA-loaded NPs notably suppressed the expression of p68/STAT3 axis in cancer cells, which was associated with blockade of tumor growth, colony formation, angiogenesis, and cancer cell migration. In addition to apoptosis induction, this combined therapy also reduced the expression of several tumor-promoting factors including Fibroblast growth factors (FGF), vascular endothelial growth factor (VEGF), transforming growth factor-β (TGF-β), matrix metallopeptidases-2 (MMP-2), MMP-9, hypoxia-inducible factor-(HIF-1α), interleukin-6 (IL-6), IL-33, Bcl-x, vimentin, and snail.

SIGNIFICANCE

These findings indicate the potential of this nano-based anti-cancer therapeutic strategy for efficient cancer therapy which should be further investigated in future studies.

Knockdown of terminal differentiation induced ncRNA (TINCR) suppresses proliferation and invasion in hepatocellular carcinoma by targeting the miR-218-5p/DEAD-box helicase 5 (DDX5) axis

Terminal differentiation induced ncRNA (TINCR), a newly identified lncRNA, has been found to be associated with different human cancers including hepatocellular carcinoma (HCC). However, little is known regarding the pathological mechanisms of TINCR in HCC progression. In this study, we confirmed that TINCR expression was upregulated in HCC tumors and cell lines, and high TINCR expression was associated with larger tumor size, advanced tumor node metastasis stage, and poor prognosis. Functionally, knockdown of TINCR facilitated apoptosis and suppressed viability, colony formation and invasion in Huh7 and Hep3B cells. Mechanically, TINCR functioned as competing endogenous RNA (ceRNA) to regulate DEAD-box helicase 5 (DDX5) expression through sponging miR-218-5p. Moreover, the miR-218-5p expression was downregulated and DDX5 expression was upregulated in HCC tumors. The silencing of miR-218-5p or ectopic expression of DDX5 abated the tumor-suppressive effect of TINCR knockdown in vitro. Furthermore, si-TINCR-induced inactivation of AKT signaling was rescued by suppression of miR-218-5p or overexpression of DDX5. Also, the silencing of TINCR resulted in tumor growth inhibition in vivo. In summary, knockdown of TINCR suppressed HCC progression presumably by inactivation of AKT signaling through targeting the miR-218-5p/DDX5 axis, suggesting a novel TINCR/miR-218-5p/DDX5 pathway and therapy target for HCC.