Nucleocytoplasmic RNA Transport Research Articles

RNAi-mediated knockdown of exportin 1 negatively affected ovary development, survival and maize mosaic virus accumulation in its insect vector Peregrinus maidis.

Exportin 1 (XPO1) is the major karyopherin-β nuclear receptor mediating the nuclear export of hundreds of proteins and some classes of RNA and regulates several critical processes in the cell, including cell-cycle progression, transcription and translation. Viruses have co-opted XPO1 to promote nucleocytoplasmic transport of viral proteins and RNA. Maize mosaic virus (MMV) is a plant-infecting rhabdovirus transmitted in a circulative propagative manner by the corn planthopper, Peregrinus maidis. MMV replicates in the nucleus of plant and insect hosts, and it remains unknown whether MMV co-opts P. maidis XPO1 (PmXPO1) to complete its life cycle. Because XPO1 plays multiple regulatory roles in cell functions and virus infection, we hypothesized that RNAi-mediated silencing of XPO1 would negatively affect MMV accumulation and insect physiology. Although PmXPO1 expression was not modulated during MMV infection, PmXPO1 knockdown negatively affected MMV accumulation in P. maidis at 12 and 15 days after microinjection. Likewise, PmXPO1 knockdown negatively affected P. maidis survival and reproduction. PmXPO1 exhibited tissue-specific expression patterns with higher expression in the ovaries compared with the guts of adult females. Survival rate was significantly lower for PmXPO1 knockdown females, compared with controls, but no effect was observed for males. PmXPO1 knockdown experiments revealed a role for PmXPO1 in ovary function and egg production. Oviposition and egg hatch on plants were dramatically reduced in females treated with dsRNA PmXPO1. These results suggest that PmXPO1 is a positive regulator of P. maidis reproduction and that it plays a proviral role in the insect vector supporting MMV infection.

Comprehensive Analysis and Drug Modulation of Human Endogenous Retrovirus in Hepatocellular Carcinomas.

Human endogenous retroviruses (HERVs) play an important role in the development of cancer and many diseases. Here, we comprehensively explored the impact of HERVs on hepatocellular carcinomas (HCCs). We employed Telescope to identify HERVs and quantify their expression in the total RNA sequencing data obtained from 254 HCC samples, comprising 254 tumor tissues and 34 matched normal tissues. In total, 3357 locus-specific activations of HERVs were differentially expressed, and 180 were correlated with patient survival. Using these 180 HERVs for classification, we found four subgroups with survival correlation. Higher expression levels of the 180 HERVs were correlated with poorer survival, while age, AFP, some mutations, and copy and structural variants differed among subgroups. The differential expression of host genes in high expression of these 180 HERVs primarily involved the activation of pathways related to immunity and infection, lipid and atherosclerosis, MAPK and NF-kB signaling, and cytokine-cytokine receptor interactions. Conversely, there was a suppression of pathways associated with RNA processing, including nucleocytoplasmic transport, surveillance and ribosome biogenesis, and transcriptional misregulation in cancer pathways. Almost all genes involved in HERV activation restriction, KRAB zinc finger proteins, RNA nucleocytoplasmic transport, stemness, HLA and antigen processing and presentation, and immune checkpoints were overexpressed in cancerous tissues, and many over-expressed HERV-related nearby genes were correlated with high HERV activation and poor survival. Twenty-three immune and stromal cells showed higher expression in non-cancerous than cancerous tissues, and seven were correlated with HERV activation. Small-molecule modulation of alternative splicing (AS) altered the expression of survival-related HERVs and their activation-related genes, as well as nearby genes. Comprehensive and integrated approaches for evaluating HERV expression and their correlation with specific pathways have the potential to provide new companion diagnostics and therapeutic strategies for HCC.

Molecular crowding and RNA synergize to promote phase separation, microtubule interaction, and seeding of Tau condensates.

Biomolecular condensation of the neuronal microtubule‐associated protein Tau (MAPT) can be induced by coacervation with polyanions like RNA, or by molecular crowding. Tau condensates have been linked to both functional microtubule binding and pathological aggregation in neurodegenerative diseases. We find that molecular crowding and coacervation with RNA, two conditions likely coexisting in the cytosol, synergize to enable Tau condensation at physiological buffer conditions and to produce condensates with a strong affinity to charged surfaces. During condensate‐mediated microtubule polymerization, their synergy enhances bundling and spatial arrangement of microtubules. We further show that different Tau condensates efficiently induce pathological Tau aggregates in cells, including accumulations at the nuclear envelope that correlate with nucleocytoplasmic transport deficits. Fluorescent lifetime imaging reveals different molecular packing densities of Tau in cellular accumulations and a condensate‐like density for nuclear‐envelope Tau. These findings suggest that a complex interplay between interaction partners, post‐translational modifications, and molecular crowding regulates the formation and function of Tau condensates. Conditions leading to prolonged existence of Tau condensates may induce the formation of seeding‐competent Tau and lead to distinct cellular Tau accumulations.

Genomic identification and expression analysis of nuclear pore proteins in Malus domestica

The nuclear pore complex (NPC), comprised of individual nucleoporin (Nup) proteins, controls nucleo-cytoplasmic transport of RNA and protein, and is important for regulating plant growth and development. However, there are no reports on this complex in fruit tree species. In this study, we identified 38 apple Nups and named them based on the known Arabidopsis thaliana homologs. We also completed bioinformatics analyses of the intron and exon structural data for apple Nups. The proteins encoded by the apple Nups lacked a universally conserved domain. Moreover, a phylogenetic analysis separated the apple and A. thaliana Nups into three groups. The phylogenetic tree indicated that MdNup54 and MdNup62 are most closely related to genes in other Rosaceae species. To characterize the 38 candidate Malus domestica Nups, we measured their stage-specific expression levels. Our tests revealed these proteins were differentially expressed among diverse tissues. We analyzed the expression levels of seven apple Nups in response to an indole-3-acetic acid (IAA) treatment. The phytohormone treatment significantly inhibited apple flowering. A qRT-PCR analysis proved that an IAA treatment significantly inhibited the expression of these seven genes. A preliminary study regarding two members of the Nup62 subcomplex, MdNup54 and MdNup62, confirmed these two proteins can interact with each other. A yeast two-hybrid assay verified that MdNup54 can interact with MdKNAT4 and MdKNAT6. On the basis of the study results, we identified apple NPC and predicted its structure and function. The data generated in this investigation provide important reference material for follow-up research.

Abstract A061: Targeting PRMT5 enhances the response to CDK4/6 inhibitors in multiple cancer types

Abstract CDK4 is a central regulator of cell cycle progression and is frequently hyper-activated by various genomic changes in numerous cancer types. CDK4/6 inhibitors such as palbociclib are approved for treatment of HR-positive breast cancer and has shown efficacy across many cancers. However, CDK4/6 inhibitors are best used in combination therapy rather than as a monotherapy. Finding novel combinations that can enhance the efficacy of CDK4/6 inhibitors and overcome or delay the emergence of resistance may provide new treatment strategies for patients.PRMT5 is an emerging target for the treatment of cancer, with the newly developed inhibitor GSK3326595 currently in phase 1/2 clinical trials.PRMT5 is a type II protein methyl-transferase that primarily catalyses the formation of symmetric di-methylarginine modifications. PRMT5 methylates the arginine residue on Histones 2A, 3 and 4 and this is considered an important epigenetic regulatory mechanism. PRMT5 can also methylate a number of non-histone proteins that govern important cellular processes including, cell signalling, RNA nucleo-cytoplasmic transport, pre-RNA processing, and ribosome biogenesis. The combined inhibition of CDK4 and PRMT5 can be seen as a promising strategy for the treatment of many cancers. A high throughput drug screen with a boutique library of targeted therapeutics was performed in order to identify potential targets whose inhibition enhances palbociclib efficacy. The effectiveness of combination treatment was evaluated by measuring cell proliferation clonogenicity, and cell death. To understand the mechanism/s of response to CDK4 and PRMT5 inhibitors, we utilized RPPA and RNA sequencing assays. In addition to this, western blotting, PCR and real-time PCR were also used to study both gene and protein expression levels as well as to validate specific targets. Furthermore, gene depletion via shRNA was performed to validate the response to these treatments. Dual inhibition of CDK4/6 and PRMT5 resulted in a robust and more durable response than the single agents in breast cancer, oesophageal, pancreatic and melanoma cell lines. The response to this combination was observed in both p53-wild type and mutant cell lines. High throughput proteomic and genomic analysis revealed that Inhibition of CDK4/6 and/or PRMT5 acts in p53-dependent and independent mechanisms. In p53 wild type, the combination of palbociclib and GSKGSK3326595 resulted in a permenant state of cell cycle arrest, whereas in p53-mutant cells the combinaiton caused mitotic catastrophe and induced cell death. In conclusion, Inhibition of PRMT5 enhances the response to CDK4/6 inhibitors and the combination of palbociclib and GSK3326595 is a potentially promising treatment strategy for various cancers. Citation Format: Shatha AbuHammad, Grant A McArthur, Karen Sheppard. Targeting PRMT5 enhances the response to CDK4/6 inhibitors in multiple cancer types [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics; 2019 Oct 26-30; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2019;18(12 Suppl):Abstract nr A061. doi:10.1158/1535-7163.TARG-19-A061

The nucleoporin ELYS regulates nuclear size by controlling NPC number and nuclear import capacity.

How intracellular organelles acquire their characteristic sizes is a fundamental question in cell biology. Given stereotypical changes in nuclear size in cancer, it is important to understand the mechanisms that control nuclear size in human cells. Using a high-throughput imaging RNAi screen, we identify and mechanistically characterize ELYS, a nucleoporin required for post-mitotic nuclear pore complex (NPC) assembly, as a determinant of nuclear size in mammalian cells. ELYS knockdown results in small nuclei, reduced nuclear lamin B2 localization, lower NPC density, and decreased nuclear import. Increasing nuclear import by importin α overexpression rescues nuclear size and lamin B2 import, while inhibiting importin α/β-mediated nuclear import decreases nuclear size. Conversely, ELYS overexpression increases nuclear size, enriches nuclear lamin B2 at the nuclear periphery, and elevates NPC density and nuclear import. Consistent with these observations, knockdown or inhibition of exportin 1 increases nuclear size. Thus, we identify ELYS as a novel positive effector of mammalian nuclear size and propose that nuclear size is sensitive to NPC density and nuclear import capacity.

EgRBP42 from oil palm enhances adaptation to stress in Arabidopsis through regulation of nucleocytoplasmic transport of stress-responsive mRNAs.

Abiotic stress reduces plant growth and crop productivity. However, the mechanism underlying posttranscriptional regulations of stress response remains elusive. Herein, we report the posttranscriptional mechanism of nucleocytoplasmic RNA transport of stress-responsive transcripts mediated by EgRBP42, a heterogeneous nuclear ribonucleoprotein-like RNA-binding protein from oil palm, which could be necessary for rapid protein translation to confer abiotic stress tolerance in plants. Transgenic Arabidopsis overexpressing EgRBP42 showed early flowering through alteration of gene expression of flowering regulators and exhibited tolerance towards heat, cold, drought, flood, and salinity stresses with enhanced poststress recovery response by increasing the expression of its target stress-responsive genes. EgRBP42 harbours nucleocytoplasmic shuttling activity mediated by the nuclear localization signal and the M9-like domain of EgRBP42 and interacts directly with regulators in the nucleus, membrane, and the cytoplasm. EgRBP42 regulates the nucleocytoplasmic RNA transport of target stress-responsive transcripts through direct binding to their AG-rich motifs. Additionally, EgRBP42 transcript and protein induction by environmental stimuli are regulated at the transcriptional and posttranscriptional levels. Taken together, the posttranscriptional regulation of RNA transport mediated by EgRBP42 may change the stress-responsive protein profiles under abiotic stress conditions leading to a better adaptation of plants to environmental changes.

Importin-8 Modulates Division of Apical Progenitors, Dendritogenesis and Tangential Migration During Development of Mouse Cortex.

The building of the brain is a multistep process that requires the coordinate expression of thousands of genes and an intense nucleocytoplasmic transport of RNA and proteins. This transport is mediated by karyopherins that comprise importins and exportins. Here, we investigated the role of the ß-importin, importin-8 (IPO8) during mouse cerebral corticogenesis as several of its cargoes have been shown to be essential during this process. First, we showed that Ipo8 mRNA is expressed in mouse brain at various embryonic ages with a clear signal in the sub-ventricular/ventricular zone (SVZ/VZ), the cerebral cortical plate (CP) and the ganglionic eminences. We found that acute knockdown of IPO8 in cortical progenitors reduced both their proliferation and cell cycle exit leading to the increase in apical progenitor pool without influencing the number of basal progenitors (BPs). Projection neurons ultimately reached their appropriate cerebral cortical layer, but their dendritogenesis was specifically affected, resulting in neurons with reduced dendrite complexity. IPO8 knockdown also slowed the migration of cortical interneurons. Together, our data demonstrate that IPO8 contribute to the coordination of several critical steps of cerebral cortex development. These results suggest that the impairment of IPO8 function might be associated with some diseases of neuronal migration defects.

RNA Nucleocytoplasmic Transport Defects in Neurodegenerative Diseases.

In eukaryotic cells, transcription and translation are compartmentalized by the nuclear membrane, requiring an active transport of RNA from the nucleus into the cytoplasm. This is accomplished by a variety of transport complexes that contain either a member of the exportin family of proteins and translocation fueled by GTP hydrolysis or in the case of mRNA by complexes containing the export protein NXF1. Recent evidence indicates that RNA transport is altered in a number of different neurodegenerative diseases including Huntington's disease, Alzheimer's disease, frontotemporal dementia, and amyotrophic lateral sclerosis. Alterations in RNA transport predominately fall into three categories: Alterations in the nuclear membrane and mislocalization and aggregation of the nucleoporins that make up the nuclear pore; alterations in the Ran gradient and the proteins that control it which impacts exportin based nuclear export; and alterations of proteins that are required for the export of mRNA leading nuclear accumulation of mRNA.

RNA Nuclear Export: From Neurological Disorders to Cancer.

The presence of a nuclear envelope, also known as nuclear membrane, defines the structural framework of all eukaryotic cells by separating the nucleus, which contains the genetic material, from the cytoplasm where the synthesis of proteins takes place. Translation of proteins in Eukaryotes is thus dependent on the active transport of DNA-encoded RNA molecules through pores embedded within the nuclear membrane. Several mechanisms are involved in this process generally referred to as RNA nuclear export or nucleocytoplasmic transport of RNA. The regulated expression of genes requires the nuclear export of protein-coding messenger RNA molecules (mRNAs) as well as non-coding RNAs (ncRNAs) together with proteins and pre-assembled ribosomal subunits. The nuclear export of mRNAs is intrinsically linked to the co-transcriptional processing of nascent transcripts synthesized by the RNA polymerase II. This functional coupling is essential for the survival of cells allowing for timely nuclear export of fully processed transcripts, which could otherwise cause the translation of abnormal proteins such as the polymeric repeat proteins produced in some neurodegenerative diseases. Alterations of the mRNA nuclear export pathways can also lead to genome instability and to various forms of cancer. This chapter will describe the molecular mechanisms driving the nuclear export of RNAs with a particular emphasis on mRNAs. It will also review their known alterations in neurological disorders and cancer, and the recent opportunities they offer for the potential development of novel therapeutic strategies.

Cytoplasmic protein aggregates interfere with nucleocytoplasmic transport of protein and RNA.

Amyloid-like protein aggregation is associated with neurodegeneration and other pathologies. The nature of the toxic aggregate species and their mechanism of action remain elusive. Here, we analyzed the compartment specificity of aggregate toxicity using artificial β-sheet proteins, as well as fragments of mutant huntingtin and TAR DNA binding protein-43 (TDP-43). Aggregation in the cytoplasm interfered with nucleocytoplasmic protein and RNA transport. In contrast, the same proteins did not inhibit transport when forming inclusions in the nucleus at or around the nucleolus. Protein aggregation in the cytoplasm, but not the nucleus, caused the sequestration and mislocalization of proteins containing disordered and low-complexity sequences, including multiple factors of the nuclear import and export machinery. Thus, impairment of nucleocytoplasmic transport may contribute to the cellular pathology of various aggregate deposition diseases.

Lysine-acetylation as a fundamental regulator of Ran function: Implications for signaling of proteins of the Ras-superfamily

The small GTP-binding protein Ran is involved in the regulation of essential cellular processes in interphase but also in mitotic cells: Ran controls the nucleocytoplasmic transport of proteins and RNA, it regulates mitotic spindle formation and nuclear envelope assembly. Deregulations in Ran dependent processes were implicated in the development of severe diseases such as cancer and neurodegenerative disorders. To understand how Ran-function is regulated is therefore of highest importance. Recently, several lysine-acetylation sites in Ran were identified by quantitative mass-spectrometry, some being located in highly important regions such as the P-loop, switch I, switch II and the G5/SAK motif. We recently reported that lysine-acetylation regulates nearly all aspects of Ran-function such as RCC1 catalyzed nucleotide exchange, intrinsic nucleotide hydrolysis, its interaction with NTF2 and the formation of import- and export-complexes. As a hint for its biological importance, we identified Ran-specific lysine-deacetylases (KDACs) and -acetyltransferases (KATs). Also for other small GTPases such as Ras, Rho, Cdc42, and for many effectors and regulators thereof, lysine-acetylation sites were discovered. However, the functional impact of lysine-acetylation as a regulator of protein function has only been marginally investigated so far. We will discuss recent findings of lysine-acetylation as a novel modification to regulate Ras-protein signaling.

Overexpressing components of the nuclear transport apparatus causes severe growth symptoms in tobacco leaves

Regulating nucleo-cytoplasmic transport of RNA and protein is a key cellular control point. Perturbing the function of plant nuclear transport components can cause significant developmental defects and in this report we add an important line to this evidence. Overexpression of AtRAN1 or AtNUP62 in Nicotiana benthamiana causes significant damage to leaf tissue. This demonstrates that the precise control of nuclear transport is an important aspect of maintaining tissue integrity.

The plant nuclear envelope and regulation of gene expression.

The nuclear envelope (NE) separates the key mechanisms of transcription and translation, and as such is a critical control point in all eukaryotic cells. In plants, the proteins of the NE influence a number of processes including the control of nucleo-cytoplasmic transport of RNA and protein, chromatin localization to the nuclear periphery, and direct chromatin binding by members of the nuclear pore complex (NPC). In this review I attempt to bring these roles under the umbrella of their effect on gene expression, even though the complex nature of this cellular environment means there is considerable overlap of effects. Although the volume of research in plant cells has greatly improved over recent years, it is clear that our understanding of how the components of the NE either directly or indirectly influence gene expression is still in its infancy.

Stress granule-defective mutants deregulate stress responsive transcripts.

To reduce expression of gene products not required under stress conditions, eukaryotic cells form large and complex cytoplasmic aggregates of RNA and proteins (stress granules; SGs), where transcripts are kept translationally inert. The overall composition of SGs, as well as their assembly requirements and regulation through stress-activated signaling pathways remain largely unknown.We have performed a genome-wide screen of S. cerevisiae gene deletion mutants for defects in SG formation upon glucose starvation stress. The screen revealed numerous genes not previously implicated in SG formation. Most mutants with strong phenotypes are equally SG defective when challenged with other stresses, but a considerable fraction is stress-specific. Proteins associated with SG defects are enriched in low-complexity regions, indicating that multiple weak macromolecule interactions are responsible for the structural integrity of SGs. Certain SG-defective mutants, but not all, display an enhanced heat-induced mutation rate. We found several mutations affecting the Ran GTPase, regulating nucleocytoplasmic transport of RNA and proteins, to confer SG defects. Unexpectedly, we found stress-regulated transcripts to reach more extreme levels in mutants unable to form SGs: stress-induced mRNAs accumulate to higher levels than in the wild-type, whereas stress-repressed mRNAs are reduced further in such mutants.Our findings are consistent with the view that, not only are SGs being regulated by stress signaling pathways, but SGs also modulate the extent of stress responses. We speculate that nucleocytoplasmic shuttling of RNA-binding proteins is required for gene expression regulation during stress, and that SGs modulate this traffic. The absence of SGs thus leads the cell to excessive, and potentially deleterious, reactions to stress.

Highly Pathogenic Avian Influenza Virus Nucleoprotein Interacts with TREX Complex Adaptor Protein Aly/REF

We constructed a novel chicken (Gallus gallus) lung cDNA library fused inside yeast acting domain vector (pGADT7). Using yeast two-hybrid screening with highly pathogenic avian influenza (HPAI) nucleoprotein (NP) from the strain (A/chicken/Malaysia/5858/2004(H5N1)) as bait, and the Gallus gallus lung cDNA library as prey, a novel interaction between the Gallus gallus cellular RNA export adaptor protein Aly/REF and the viral NP was identified. This interaction was confirmed and validated with mammalian two hybrid studies and co-immunoprecipitation assay. Cellular localization studies using confocal microscopy showed that NP and Aly/REF co-localize primarily in the nucleus. Further investigations by mammalian two hybrid studies into the binding of NP of other subtypes of influenza virus such as the swine A/New Jersey/1976/H1N1 and pandemic A/Malaysia/854/2009(H1N1) to human Aly/REF, also showed that the NP of these viruses interacts with human Aly/REF. Our findings are also supported by docking studies which showed tight and favorable binding between H5N1 NP and human Aly/REF, using crystal structures from Protein Data Bank. siRNA knockdown of Aly/REF had little effect on the export of HPAI NP and other viral RNA as it showed no significant reduction in virus titer. However, UAP56, another component of the TREX complex, which recruits Aly/REF to mRNA was found to interact even better with H5N1 NP through molecular docking studies. Both these proteins also co-localizes in the nucleus at early infection similar to Aly/REF. Intriguingly, knockdown of UAP56 in A549 infected cells shows significant reduction in viral titer (close to 10 fold reduction). Conclusively, our study have opened new avenues for research of other cellular RNA export adaptors crucial in aiding viral RNA export such as the SRSF3, 9G8 and ASF/SF2 that may play role in influenza virus RNA nucleocytoplasmic transport.

High-resolution three-dimensional mapping of mRNA export through the nuclear pore.

The flow of genetic information is regulated by selective nucleocytoplasmic transport of messenger RNA:protein complexes (mRNPs) through the nuclear pore complexes (NPCs) of eukaryotic cells. However, the three-dimensional pathway taken by mRNPs as they transit through the NPC, and the kinetics and selectivity of transport, remain obscure. Here we employ single-molecule fluorescence microscopy with an unprecedented spatiotemporal accuracy of 8 nm and 2 ms to provide new insights into the mechanism of nuclear mRNP export in live human cells. We find that mRNPs exiting the nucleus are decelerated and selected at the centre of the NPC, and adopt a fast-slow-fast diffusion pattern during their brief, ~12 ms interaction with the NPC. A 3D reconstruction of the export route indicates that mRNPs primarily interact with the periphery on the nucleoplasmic side and in the center of the NPC, without entering the central axial conduit utilized for passive diffusion of small molecules, and eventually dissociate on the cytoplasmic side.

Identification of GSX2 and AF10 as NUP98 partner genes in myeloid malignancies

Identification of GSX2 and AF10 as NUP98 partner genes in myeloid malignancies

Three-Dimensional Mapping Nuclear Export of Single mRNAs with Exceptional Spatiotemporal Accuracy

In eukaryotic cells, the flow of genetic information is regulated by selective nucleocytoplasmic transport of individual messenger RNA:protein complexes (mRNPs) through the nuclear pore complex (NPC). Each NPC, ∼200 nm in length and ∼50 nm in inner diameter, is a large assembly of multiple copies of ∼30 nucleoporins. However, the nuclear export kinetics, three-dimensional (3D) pathway and selectivity step of mRNPs transiting an individual NPCs remain poorly understood. Here we employ single-molecule fluorescence microscopy with an unprecedented spatiotemporal super-accuracy of 8 nm and 2 ms to characterize nuclear mRNP export in living cells. We find that, mRNPs exiting the nucleus are decelerated and selected at the narrowest region of the NPC, and adopt a fast-slow-fast diffusion pattern as they translocate through the NPC. 3D mapping translocation pathway for mRNPs further indicates only one third of all mRNAs successfully transits during their ∼12-ms interaction with the NPC, primarily follow the periphery on the nucleoplasmic side and in the center of the NPC without occupying central axial conduit utilized for passive diffusion of small molecules, and eventually dissociating from the cytoplasmic side.

High Ran level is correlated with poor prognosis in patients with colorectal cancer

The Ras-like nuclear protein (Ran) is involved in the regulation of nuclear transport, microtubule nucleation and dynamics, and spindle assembly. Its fundamental function is nucleocytoplasmic transport of RNA and proteins. The expression and potential role of Ran in colorectal cancer (CRC) remain unclear. The aim of this study was to investigate the relationship between Ran expression and CRC characteristics. The potential role of Ran as a prognostic indicator was also evaluated. We used immunohistochemistry and western blotting to detect Ran expression in 287 CRC tissues. The relationships between Ran expression and clinicopathological characteristics and overall survival rate were statistically analyzed. CRC tissues had significantly higher Ran expression than normal colorectal epithelial cells. Ran was positively correlated with depth of invasion, lymph node metastases, distant metastases, tumor differentiation, and tumor-node-metastasis stage. However, no correlation was found between Ran expression and patient age or sex. The overall survival rate was consistently and significantly lower in patients with Ran-positive tumors than in those with Ran-negative tumors. Our findings emphasize the important role of Ran in differentiation, disease stage, and metastasis in human CRC. Ran may play an important role in the development of CRC and may serve as a novel prognostic indicator of CRC.