hnRNP Q1 Research Articles

A viral interferon regulatory factor degrades RNA-binding protein hnRNP Q1 to enhance aerobic glycolysis via recruiting E3 ubiquitin ligase KLHL3 and decaying GDPD1 mRNA.

Reprogramming of host metabolism is a common strategy of viral evasion of host cells, and is essential for successful viral infection and induction of cancer in the context cancer viruses. Kaposi's sarcoma (KS) is the most common AIDS-associated cancer caused by KS-associated herpesvirus (KSHV) infection. KSHV-encoded viral interferon regulatory factor 1 (vIRF1) regulates multiple signaling pathways and plays an important role in KSHV infection and oncogenesis. However, the role of vIRF1 in KSHV-induced metabolic reprogramming remains elusive. Here we show that vIRF1 increases glucose uptake, ATP production and lactate secretion by downregulating heterogeneous nuclear ribonuclear protein Q1 (hnRNP Q1). Mechanistically, vIRF1 upregulates and recruits E3 ubiquitin ligase Kelch-like 3 (KLHL3) to degrade hnRNP Q1 through a ubiquitin-proteasome pathway. Furthermore, hnRNP Q1 binds to and stabilizes the mRNA of glycerophosphodiester phosphodiesterase domain containing 1 (GDPD1). However, vIRF1 targets hnRNP Q1 for degradation, which destabilizes GDPD1 mRNA, resulting in induction of aerobic glycolysis. These results reveal a novel role of vIRF1 in KSHV metabolic reprogramming, and identifying a potential therapeutic target for KSHV infection and KSHV-induced cancers.

Abstract 4387: hnRNP Q1 promotes cell proliferation and tumorigenesis by translationally up-regulating cell cycle-related genes through the EGF pathway

Abstract Heterogeneous nuclear ribonucleoprotein (hnRNP) Q1, an RNA-binding protein, has been reported as overexpressing in cancer cells. However, the role of hnRNP Q1 in tumorigenesis remains unclear. By using RNA-immunoprecipitation (IP) assay following next-generation sequencing, a group of cell cycle-related genes targeted by hnRNP Q1 were identified, including Aurora-A kinase. Overexpressed hnNRP Q1 can up-regulate Aurora-A and many spindle assembly checkpoint (SAC) proteins, but not alter their mRNA levels, through enhancing translational efficiency by interacting with the mRNA 5’-UTR. Ribosomal S6-IP and ribosomal profiling assay further confirmed the translational regulation of these mRNAs by hnRNP Q1. Stimulation with epidermal growth factor (EGF) enhances both binding between hnRNP Q1 and these mRNAs as well as the efficacy of the hnRNP Q1-induced translation of these mRNAs. EGF/hnRNP Q1-induced translation is mediated by the mTOR and ERK pathways. In addition, hnRNP Q1 overexpression is positively correlated with the levels of Aurora-A and these SAC genes in human colorectal cancer tissues. Taken together, our data suggest that hnRNP Q1 plays an important role in translationally regulating the expression of Aurora-A and a group of cell cycle-related genes, which increases cell proliferation and contributes to tumorigenesis in colorectal cancer. It may thereby contribute to tumorigenesis by translationally up-regulating these genes in colorectal cancer. Citation Format: Liang-Yi Hung. hnRNP Q1 promotes cell proliferation and tumorigenesis by translationally up-regulating cell cycle-related genes through the EGF pathway [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4387.

The EGF/hnRNP Q1 axis is involved in tumorigenesis via the regulation of cell cycle-related genes

Heterogeneous nuclear ribonucleoprotein (hnRNP) Q1, an RNA-binding protein, has been implicated in many post-transcriptional processes, including RNA metabolism and mRNA splicing and translation. However, the role of hnRNP Q1 in tumorigenesis remains unclear. We previously performed RNA immunoprecipitation (RIP)-seq analysis to identify hnRNP Q1-interacting mRNAs and found that hnRNP Q1 targets a group of genes that are involved in mitotic regulation, including Aurora-A. Here, we demonstrate that altering the hnRNP Q1 level influences the expression of the Aurora-A protein, but not its mRNA. Stimulation with epidermal growth factor (EGF) enhances both binding between hnRNP Q1 and Aurora-A mRNA as well as the efficacy of the hnRNP Q1-induced translation of Aurora-A mRNA. The EGF/hnRNP Q1-induced translation of Aurora-A mRNA is mediated by the mTOR and ERK pathways. In addition, we show that hnRNP Q1 up-regulates the translation of a group of spindle assembly checkpoint (SAC) genes. hnRNP Q1 overexpression is positively correlated with the levels of Aurora-A and the SAC genes in human colorectal cancer tissues. In summary, our data suggest that hnRNP Q1 plays an important role in regulating the expression of a group of cell cycle-related genes. Therefore, it may contribute to tumorigenesis by up-regulating the translation of these genes in colorectal cancer.

Abstract 4477: HnRNP Q1 translationally increases the expression of Aurora-A and promotes tumorigenesis in colorectal cancer

Abstract Abnormally elevated Aurora-A can cause mitotic defects and aneuploidy, which might lead to genomic instability and tumorigenesis. According to the literatures, overexpressed Aurora-A may result from gene amplification, RNA transcriptional activation, or increased protein stability. Our previous study has demonstrated that Aurora-A can be translational upregulated in colorectal cancer. By biotin pull-down assay and in vivo translational assay, we found that Aurora-A mRNA can be translational upregulated by heterogeneous nuclear ribonucleoprotein (hnRNP) Q1, a RNA binding protein. Hn RNP Q1 has been implicated in many posttranscriptional regulatory processes including mRNA splicing, RNA metabolism and translation. In this study, we further clarified the regulatory mechanism of hnRNP Q1 in translational regulating Aurora-A mRNA, as well as investigated the clinical role of hnRNP Q1 in colorectal carcinogenesis. Our results indicated that hnRNP Q1 can bind to the Aurora-A mRNA 5’-untranslated region (5’-UTR). Ribosomal protein S6-IP assay further indicated that hnRNP Q1 can enhance the translational efficacy of Aurora-A mRNA. Ribosomal profiling assay further confirmed the translational regulation of Aurora-A mRNA by hnRNP Q1. Overexpression of hnRNP Q1 promotes cell proliferation and tumor growth. The expression level of hnRNP Q1 is positively correlated with Aurora-A in colorectal cancer. Taken together, our data indicate hnRNP Q1 is a novel trans-acting factor that binds to Aurora-A mRNA 5’-UTRs and regulates its translation, which increases cell proliferation and contributes to tumorigenesis in colorectal cancer. Citation Format: Liang-Yi Hung. HnRNP Q1 translationally increases the expression of Aurora-A and promotes tumorigenesis in colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4477. doi:10.1158/1538-7445.AM2017-4477

Translational upregulation of Aurora-A by hnRNP Q1 contributes to cell proliferation and tumorigenesis in colorectal cancer

By using RNA-immunoprecipitation assay following next-generation sequencing, a group of cell cycle-related genes targeted by hnRNP Q1 were identified, including Aurora-A kinase. Overexpressed hnRNP Q1 can upregulate Aurora-A protein, but not alter the mRNA level, through enhancing the translational efficiency of Aurora-A mRNA, either in a cap-dependent or -independent manner, by interacting with the 5′-UTR of Aurora-A mRNA through its RNA-binding domains (RBDs) 2 and 3. By ribosomal profiling assay further confirmed the translational regulation of Aurora-A mRNA by hnRNP Q1. Overexpression of hnRNP Q1 promotes cell proliferation and tumor growth. HnRNP Q1/ΔRBD23-truncated mutant, which loses the binding ability and translational regulation of Aurora-A mRNA, has no effect on promoting tumor growth. The expression level of hnRNP Q1 is positively correlated with Aurora-A in colorectal cancer. Taken together, our data indicate that hnRNP Q1 is a novel trans-acting factor that binds to Aurora-A mRNA 5′-UTRs and regulates its translation, which increases cell proliferation and contributes to tumorigenesis in colorectal cancer.

Abstract 2882: HnRNP Q1, a novel translational regulator for Aurora-A protein synthesis in colorectal cancer

Abstract HnRNP Q1 is a multifunctional RNA-binding protein and has an abundant expression level compared with hnRNP Q member. In colorectal cancer, hnRNP Q has been reported to associate with cell proliferation, but the underlying mechanism is still unclear. By RNA-immunoprecipitation assay following next-generation sequencing (NGS), a group of cell cycle-related genes was identified to be targeted by hnRNP Q1, including Aurora-A kinase. Aurora-A is a cell cycle dependent kinase involved in regulating centrosome duplication, maturation and spindle assembly during mitosis. Abnormally elevated Aurora-A will cause mitotic defects and aneuploidy, which might lead to genomic instability and tumorigenesis. Our previous work has demonstrated that Aurora-A can be translational up-regulated in colorectal cancer. In order to investigate the role of hnRNP Q1 in Aurora-A expression, GFP-hnNRP Q1 was overexpressed in colorectal cancer cells. We found that Aurora-A protein, but not the mRNA level, was up-regulated in those GFP-hnRNP Q1-overexpressing cells. By biotin pull down and Biacore analysis, we revealed that hnRNP Q1 binds to the 5’-UTRs of Aurora-A mRNA directly, and their interacting domain was mapped. Importantly, we found that hnRNP Q1 can enhance Aurora-A protein synthesis through IRES-mediated translational regulation in a cell cycle-regulated manner by ribosomal protein S6 immunoprecipitation, polysome fractionation and bicistronic reporter assay. CCK-8 assay, colony formation and in vivo xenograft assay all suggested that overexpression of hnRNP Q1 can promote cell proliferation and tumorigenesis of colorectal cancer cells. In addition, the expression level of hnRNP Q1 is positively correlated with Aurora-A in clinical colorectal cancer tissues. Taken together, our data indicate that hnRNP Q1 is a novel trans-acting factor that binds to Aurora-A 5’-UTRs and regulates its translation, which may increase cell proliferation and contribute to the tumorigenesis of colorectal cancer. Citation Format: Chien-Hsien Lai, Liang-Yi Hung. HnRNP Q1, a novel translational regulator for Aurora-A protein synthesis in colorectal cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2882.

Abstract 2127: HnRNP Q1 contributes to tumorigenesis through the translational regulation of Aurora-A in colorectal cancer

Abstract HnRNP Q1 is a RNA-binding protein which belongs to hnRNP Q family and involves in pre-mRNA splicing, mRNA transport, translation and turnover. Data from Oncomine, which is a cancer microarray database, indicates that hnRNP Q1 is overexpressed in colorectal cancer. According the literatures, hnRNP Q1 can increase the translational efficiency through binding to the 5′-untranslated region (5′-UTR) of target genes. From RNA-IP assay following the next generation sequencing (NGS), we found that hnRNP Q1 regulates a group of cell cycle-related genes. Among them, Aurora-A is one of the targets of hnRNP Q1. Aurora-A is a cell-cycle dependent kinase involved in regulating centrosome duplication, maturation, and spindle assembly during mitosis. Abnormally elevated Aurora-A will cause mitotic defect and aneuploidy, which might lead to genomic instability and tumorigenesis. In addition, overexpression of hnRNP Q1 is positively correlated with overexpressed Aurora-A in clinical colorectal cancer tissues. Our previous report demonstrated that Aurora-A can be translational up-regulated in colorectal cancer. In this study, we demonstrated that hnRNP Q1 can bind to Aurora-A 5′-UTRs and also mapped the interacting domain between Aurora-A 5′UTR and hnRNP Q1 has been mapped by Biacore analysis, RNA-IP and biotin pull-down assay. Overexpressed hnRNP Q1 enhances the Aurora-A protein expression but doesn't alter its mRNA level. In contrast, repressed expression of hnRNP Q1 decreases the translation of Aurora-A. Importantly, we found that Aurora-A 5′UTR has IRES-dependent translational activity in a cell cycle regulated manner. Overexpression of hnRNP Q1 can up-regulate the IRES-dependent translation of Aurora-A during cell cycle progression, and promotes the cells proliferation. Taken together, our data indicate hnRNP Q1 is a novel trans-acting factor that binds on the Aurora-A 5′-UTRs and regulates it's translation, which may increase the cell proliferation and contribute to the tumorigenesis of colorectal cancer. Citation Format: Liang-Yi Hung. HnRNP Q1 contributes to tumorigenesis through the translational regulation of Aurora-A in colorectal cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2127. doi:10.1158/1538-7445.AM2015-2127

HnRNP Q Regulates Cdc42-Mediated Neuronal Morphogenesis

The RNA-binding protein hnRNP Q has been implicated in neuronal mRNA metabolism. Here, we show that knockdown of hnRNP Q increased neurite complexity in cultured rat cortical neurons and induced filopodium formation in mouse neuroblastoma cells. Reexpression of hnRNP Q1 in hnRNP Q-depleted cells abrogated the morphological changes of neurites, indicating a specific role for hnRNP Q1 in neuronal morphogenesis. A search for mRNA targets of hnRNP Q1 identified functionally coherent sets of mRNAs encoding factors involved in cellular signaling or cytoskeletal regulation and determined its preferred binding sequences. We demonstrated that hnRNP Q1 bound to a set of identified mRNAs encoding the components of the actin nucleation-promoting Cdc42/N-WASP/Arp2/3 complex and was in part colocalized with Cdc42 mRNA in granules. Using subcellular fractionation and immunofluorescence, we showed that knockdown of hnRNP Q reduced the level of some of those mRNAs in neurites and redistributed their encoded proteins from neurite tips to soma to different extents. Overexpression of dominant negative mutants of Cdc42 or N-WASP compromised hnRNP Q depletion-induced neurite complexity. Together, our results suggest that hnRNP Q1 may participate in localization of mRNAs encoding Cdc42 signaling factors in neurites, and thereby may regulate actin dynamics and control neuronal morphogenesis.

Negative regulation of RhoA translation and signaling by hnRNP-Q1 affects cellular morphogenesis

The small GTPase RhoA has critical functions in regulating actin dynamics affecting cellular morphogenesis through the RhoA/Rho kinase (ROCK) signaling cascade. RhoA signaling controls stress fiber and focal adhesion formation and cell motility in fibroblasts. RhoA signaling is involved in several aspects of neuronal development, including neuronal migration, growth cone collapse, dendrite branching, and spine growth. Altered RhoA signaling is implicated in cancer and neurodegenerative disease and is linked to inherited intellectual disabilities. Although much is known about factors regulating RhoA activity and/or degradation, little is known about molecular mechanisms regulating RhoA expression and the subsequent effects on RhoA signaling. We hypothesized that posttranscriptional control of RhoA expression may provide a mechanism to regulate RhoA signaling and downstream effects on cell morphology. Here we uncover a cellular function for the mRNA-binding protein heterogeneous nuclear ribonucleoprotein (hnRNP) Q1 in the control of dendritic development and focal adhesion formation that involves the negative regulation of RhoA synthesis and signaling. We show that hnRNP-Q1 represses RhoA translation and knockdown of hnRNP-Q1 induced phenotypes associated with elevated RhoA protein levels and RhoA/ROCK signaling. These morphological changes were rescued by ROCK inhibition and/or RhoA knockdown. These findings further suggest that negative modulation of RhoA mRNA translation can provide control over downstream signaling and cellular morphogenesis.

The RNA Binding Protein hnRNP Q Modulates the Utilization of Exon 7 in the Survival Motor Neuron 2 (SMN2) Gene

Spinal muscular atrophy (SMA) is a recessive neuromuscular disorder caused by the homozygous loss of the SMN1 gene. The human SMN2 gene has a C-to-T transition at position +6 of exon 7 and thus produces exon 7-skipping mRNAs. However, we observed an unexpectedly high level of exon 7-containing SMN2 transcripts as well as SMN protein in testis of smn(-/-) SMN2 transgenic mice. Using affinity chromatography, we identified several SMN RNA-associating proteins in mouse testis and human HeLa cells, including hnRNP Q. The major hnRNP Q isoform, Q1, directly bound SMN exon 7 in the vicinity of nucleotide +6. Overexpression of hnRNP Q1 promoted the inclusion of exon 7 in SMN2, probably by activating the use of its upstream 3' splice site. However, the minor isoforms Q2/Q3 could antagonize the activity of hnRNP Q1 and induced exon 7 exclusion. Intriguingly, enhanced exon 7 inclusion was also observed upon concomitant depletion of three hnRNP Q isoforms. Thus, differential expression of hnRNP Q isoforms may result in intricate control of SMN precursor mRNA splicing. Here, we demonstrate that hnRNP Q is a splicing modulator of SMN, further underscoring the potential of hnRNP Q as a therapeutic target for SMA.