Inherited nuclear pore substructures template post-mitotic pore assembly.

Nuclear envelope assembly during late mitosis includes rapid formation of several thousand complete nuclear pore complexes (NPCs). This efficient use of NPC components (nucleoporins or "NUPs") is essential for ensuring immediate nucleocytoplasmic communication in each daughter cell. We show that octameric subassemblies of outer and inner nuclear pore rings remain intact in the mitotic endoplasmic reticulum (ER) after NPC disassembly during prophase. These "inherited" subassemblies then incorporate into NPCs during post-mitotic pore formation. We further show that the stable subassemblies persist through multiple rounds of cell division and the accompanying rounds of NPC mitotic disassembly and post-mitotic assembly. De novo formation of NPCs from newly synthesized NUPs during interphase will then have a distinct initiation mechanism. We postulate that a yet-to-be-identified modification marks and "immortalizes" one or more components of the specific octameric outer and inner ring subcomplexes that then template post-mitotic NPC assembly during subsequent cell cycles.

hsa-miR-191-5p inhibits replication of human immunodeficiency virus type 1 by downregulating the expression of NUP50.

MicroRNAs (miRNAs) are important host molecules involved in human immunodeficiency virus type 1 (HIV-1) infection. Antiretroviral therapy (ART) can affect the miRNA expression profile, but differentially expressed miRNAs still remain to be identified. In this study, we used gene chips to analyze miRNA expression profiles in peripheral blood mononuclear cells from ART-naive HIV-1 patients and those receiving ART, as well as from uninfected individuals. We measured differences in miRNA expression by quantitative polymerase chain reaction (qPCR) in an expanded sample. We found significant differences in the expression of has-miR-191-5p among the three groups (P < 0.05). Furthermore, we showed that hsa-miR-191-5p has an inhibitory effect on HIV-1 replication in cell models in vitro. We identified CCR1 and NUP50 as target molecules of hsa-miR-191-5p and found that hsa-miR-191-5p inhibits the expression of CCR1 and NUP50. Knockdown of NUP50 resulted in significant inhibition of HIV-1 replication. In summary, our research shows that hsa-miR-191-5p expression is reduced in HIV-1-infected patients and acts an inhibitor of HIV-1 infection via a mechanism that may involve targeted repression of NUP50 expression.

TMEM48 promotes cell proliferation and invasion in cervical cancer via activation of the Wnt/ß-catenin pathway.

Transmembrane proteins (TMEMs), spanning the entire width of lipid bilayers and anchored to them permanently, exist in diverse cell types to implement a series of essential physiological functions. Recently, TMEM48, a member of the TMEM family, has been demonstrated to be closely associated with tumorigenesis. However, little is known about the specific role of TMEM48 in cervical cancer (CC). This study aimed to investigate the biological functions of TMEM48 in CC. The CCK-8 assay was performed to detect CC cell proliferation. The wound healing and transwell assays were conducted to measure cell migration and invasion, respectively. The levels of TMEM48, ß-catenin, T cell factor 1(TCF1) and axis formation inhibitor 2 (AXIN2) were examined by the western blot analysis. Xenograft models were established for the tumorigenesis assay in vivo. The results showed that TMEM48 was overexpressed in CC tissues and cell lines. Knockdown of TMEM48 significantly inhibited CC cell proliferation, migration and invasion in vitro and suppressed CC cell growth in vivo. In addition, the investigation on the molecular mechanisms indicated that TMEM48 down-regulation remarkably decreased the protein levels of ß-catenin, TCF1 and AXIN2 in CC cells and TMEM48 exerted its promoting effect on CC progression via activation of the Wnt/ß-catenin pathway. Taken together, our study suggested TMEM48 as a promising therapeutic target for CC treatment.

CircAGFG1 sponges miR-203 to promote EMT and metastasis of non-small-cell lung cancer by upregulating ZNF281 expression.

The circRNA circAGFG1 is reported to be important in triple-negative breast cancer progression. However, the mechanism of circAGFG1 in non-small-cell lung cancer (NSCLC) remains unknown. In this study, expression of circAGFG1 was determined by real-time PCR in 20 pairs of NSCLC tissues and adjacent tissues. Next, functional experiments with circAGFG1 were performed in vitro to evaluate the role of circAGFG1 in tumor metastasis and growth. Meanwhile, a dual luciferase reporter assay, RNA pull-down and RNA immunoprecipitation experiments were used to explore the interaction between circAGFG1 and miR-203. Our results revealed that expression levels of circAGFG1 and miR-203 are upregulated in non-small-cell lung cancer tissues. CircAGFG1 enhances NSCLC cell proliferation, invasion, migration and epithelial-mesenchymal transition in vitro. Mechanistic analyses indicated that circAGFG1 acts as a sponge for miR-203 to repress the effect of miR-203 on its target, ZNF281. In conclusion, our study suggests that circAGFG1 promotes NSCLC growth and metastasis though a circAGFG1/miR-203/ZNF281 axis and may represent a novel therapeutic target.

Epigenetic-genetic chromatin footprinting identifies novel and subject-specific genes active in prefrontal cortex neurons.

Human prefrontal cortex (PFC) is associated with broad individual variabilities in functions linked to personality, social behaviors, and cognitive functions. The phenotype variabilities associated with brain functions can be caused by genetic or epigenetic factors. The interactions between these factors in human subjects is, as of yet, poorly understood. The heterogeneity of cerebral tissue, consisting of neuronal and nonneuronal cells, complicates the comparative analysis of gene activities in brain specimens. To approach the underlying neurogenomic determinants, we performed a deep analysis of open chromatin-associated histone methylation in PFC neurons sorted from multiple human individuals in conjunction with whole-genome and transcriptome sequencing. Integrative analyses produced novel unannotated neuronal genes and revealed individual-specific chromatin "blueprints" of neurons that, in part, relate to genetic background. Surprisingly, we observed gender-dependent epigenetic signals, implying that gender may contribute to the chromatin variabilities in neurons. Finally, we found epigenetic, allele-specific activation of the testis-specific gene nucleoporin 210 like (NUP210L) in brain in some individuals, which we link to a genetic variant occurring in <3% of the human population. Recently, the NUP210L locus has been associated with intelligence and mathematics ability. Our findings highlight the significance of epigenetic-genetic footprinting for exploring neurologic function in a subject-specific manner.-Gusev, F. E., Reshetov, D. A., Mitchell, A. C., Andreeva, T. V., Dincer, A., Grigorenko, A. P., Fedonin, G., Halene, T., Aliseychik, M., Goltsov, A. Y., Solovyev, V., Brizgalov, L., Filippova, E., Weng, Z., Akbarian, S., Rogaev, E. I. Epigenetic-genetic chromatin footprinting identifies novel and subject-specific genes active in prefrontal cortex neurons.

Molecular assay for an intronic variant in NUP93 that causes steroid resistant nephrotic syndrome.

Advances in molecular genetics have revealed that approximately 30% of cases with steroid-resistant nephrotic syndrome (SRNS) are caused by single-gene mutations. More than 50 genes are responsible for SRNS. One such gene is the nucleoporin, 93-KD (NUP93). Thus far, few studies have reported mutations of NUP93 in SRNS. Here, we describe an NUP93 biallelic mutation in a 9-year-old boy with focal segmental glomerular sclerosis (FSGS). Notably, one mutation comprised an intronic variant; we conducted in vivo and in vitro analysis to characterize this variant. We found two heterozygous mutations in NUP93: c.2137-18G>A in intron 19 and a novel nonsense mutation c.727A>T (p.Lys243*) in exon 8. We conducted RNA sequencing and in vitro splicing assays by using minigene construction, combined with protein expression analysis to determine the pathogenicity of the intronic variant. Both RNA sequencing and in vitro splicing assay showed exon 20-skipping by the intronic variant. In protein expression analysis, aberrant subcellular localization with small punctate vesicles in the cytoplasm was observed for the intronic variant. Taken together, we concluded that c.2137-18G>A was linked to pathogenicity due to aberrant splicing. NUP93 variants are quite rare; however, we have shown that even intronic variants in NUP93 can cause SRNS. This study provides a fundamental approach to validate the intronic variant, as well as new insights regarding the clinical spectrum of SRNS caused by rare gene variants.

HIV-1 infection increases microRNAs that inhibit Dicer1, HRB and HIV-EP2, thereby reducing viral replication.

HIV-1 is the causative agent of AIDS (Autoimmune Deficiency Syndrome). HIV-1 infection results in systemic CD4+ T cell depletion, thereby impairing cell-mediated immunity. MicroRNAs are short (~22 nucleotides long), endogenous single-stranded RNA molecules that regulate gene expression by binding to the 3' untranslated regions (3' UTR) of mRNA transcripts. The relation between HIV-1 infection and human miRNA expression profile has been previously investigated, and studies have shown that the virus can alter miRNA expression and vice versa. Here, we broaden the understanding of the HIV-1 infection process, and show that miRNA-186, 210 and 222 are up-regulated following HIV-1 infection of human Sup-T1 cells. As a result, the host miRNA target genes: Dicer1 (Double-Stranded RNA-Specific Endoribonuclease), HRB (HIV-1 Rev-binding protein) and HIV-EP2 (Human Immunodeficiency Virus Type I Enhancer Binding Protein 2), are down-regulated. Moreover, testing the miRNA-gene anti- correlation on the Jurkat and the HeLa-MAGI cell lines demonstrated the ability of the miRNAs to down-regulate viral expression as well. To conclude, we found that human miR-186, 210 and 222 directly regulate the human genes Dicer1, HRB and HIV-EP2, thus may be filling key roles during HIV-1 replication and miRNA biogenesis. This finding may contribute to the development of new therapeutic strategies.

Dhh1 is a member of the SESA network.

The correct separation of chromosomes during mitosis is necessary to prevent genetic instability and aneuploidy, which are responsible for cancer and other diseases, and it depends on proper centrosome duplication. In a recent study, we found that Smy2 can suppress the essential role of Mps2 in the insertion of yeast centrosome into the nuclear membrane by interacting with Eap1, Scp160, and Asc1 and designated this network as SESA (Smy2, Eap1, Scp160, Asc1). Detailed analysis showed that the SESA network is part of a mechanism which regulates translation of POM34 mRNA. Thus, SESA is a system that suppresses spindle pole body duplication defects by repressing the translation of POM34 mRNA. In this study, we performed a genome-wide screening in order to identify new members of the SESA network and confirmed Dhh1 as a putative member. Dhh1 is a cytoplasmic DEAD-box helicase known to regulate translation. Therefore, we hypothesized that Dhh1 is responsible for the highly selective inhibition of POM34 mRNA by SESA.

Differential Expression of Sumoylation Enzymes SAE1, U BA2, UBC9, PIAS1 and RanBP2 in Major Ocular Tissues of Mouse Eye.

Background: It is now well established that protein sumoylation is an important mechanism to regulate multiple cellular processes including gene transcription, chromatin structure, cell proliferation and differentiation, as well as pathogenesis. Objective: In the vertebrate eye, we and others have previously shown that sumoylation can regulate differentiation of major ocular tissues including retina and lens. However, the expression patterns of the three types of sumoylation enzymes, the activating enzymes SAE1 and UBA2, the conjugating enzyme UBC9, and the ligating enzymes such as RanBP2 and PIAS1 have not been well studied in the ocular tissues. Conclusion: In the present study, using QRT-PCR and western blot analysis, we have determined the differentiatial expression patterns of the above three types of enzymes, and the obtained results lay down a foundation for further exploration of sumoylation functions in vertebrate eye.

High-mobility group box 1 protein-mediated necroptosis contributes to dasatinib-induced cardiotoxicity.

Dasatinib shows remarkable activity against imatinib-refractory chronic myelogenous leukemia (CML) and Philadelphia chromosome positive acute lymphoblastic leukemia (Ph+ALL). However, severe cardiovascular toxicity limits the clinical applications of dasatinib. Since the underlying mechanism of dasatinib-induced cardiotoxicity is still elusive, we aim to clarify this. Recent studies have shown that necroptosis and apoptosis participate in multiple toxicity development. Here, we first report that dasatinib could directly induce cardiomyocytes death, as analyzed by the Sulforhodamine B (SRB) assay. This type of cardiomyocytes death was mediated by the necrosis pathway rather than apoptosis, as determined by using flow cytometry to characterize the mode of dasatinib-induced cell death. Inhibition of receptor-interacting protein kinase 1 (RIP1)activity and knockdown of receptor-interacting protein kinase 3 (RIP3)expression can block dasatinib-evoked cardiotoxicity, which further confirmed the involvement of necroptosis. We next found that the classic substrates of RIP3, mixed lineage kinase domain-like protein (MLKL) and Ca2+-calmodulin-dependent protein kinase II (CaMKII) were not involved in dasatinib-induced cardiomyocytes necroptosis. What's more, unlike the inflammation-associated necroptosis, dasatinib-triggered necroptosis was dependent on intracellular instead of secreted High-mobility group box 1 (HMGB1) protein. Collectively, our study revealed that dasatinib-induced cardiotoxicity acted via leading cardiomyocytes to HMGB1-mediated necroptosis, indicating a viable strategy for prevention of dasatinib-induced cardiotoxicity.

An Arabidopsis Nucleoporin NUP85 modulates plant responses to ABA and salt stress.

Several nucleoporins in the nuclear pore complex (NPC) have been reported to be involved in abiotic stress responses in plants. However, the molecular mechanism of how NPC regulates abiotic stress responses, especially the expression of stress responsive genes remains poorly understood. From a forward genetics screen using an abiotic stress-responsive luciferase reporter (RD29A-LUC) in the sickle-1 (sic-1) mutant background, we identified a suppressor caused by a mutation in NUCLEOPORIN 85 (NUP85), which exhibited reduced expression of RD29A-LUC in response to ABA and salt stress. Consistently, the ABA and salinity induced expression of several stress responsive genes such as RD29A, COR15A and COR47 was significantly compromised in nup85 mutants and other nucleoporin mutants such as nup160 and hos1. Subsequently, Immunoprecipitation and mass spectrometry analysis revealed that NUP85 is potentially associated with HOS1 and other nucleoporins within the nup107-160 complex, along with several mediator subunits. We further showed that there is a direct physical interaction between MED18 and NUP85. Similar to NUP85 mutations, MED18 mutation was also found to attenuate expression of stress responsive genes. Taken together, we not only revealed the involvement of NUP85 and other nucleoporins in regulating ABA and salt stress responses, but also uncovered a potential relation between NPC and mediator complex in modulating the gene expression in plants.

Identification and Preparation of a Novel Chemokine Receptor-Binding Domain in the Cytoplasmic Regulator FROUNT.

FROUNT is a cytoplasmic protein that binds to the membrane-proximal C-terminal regions (Pro-Cs) of chemokine receptors, CCR2 and CCR5. The FROUNT-chemokine receptor interactions play a pivotal role in the migration of inflammatory immune cells, indicating the potential of FROUNT as a drug target for inflammatory diseases. To provide the foundation for drug development, structural information of the Pro-C binding region of FROUNT is desired. Here, we defined the novel structural domain (FNT-CB), which mediates the interaction with the chemokine receptors. A recombinant GST-tag-fused FNT-CB protein expression system was constructed. The protein was purified by affinity chromatography and then subjected to in-gel protease digestion of the GST-tag. The released FNT-CB was further purified by anion-exchange and size-exclusion chromatography. Purified FNT-CB adopts a helical structure, as indicated by CD. NMR line-broadening indicated that weak aggregation occurred at sub-millimolar concentrations, but the line-broadening was mitigated by using a deuterated sample in concert with transverse relaxation-optimized spectroscopy. The specific binding of FNT-CB to CCR2 Pro-C was confirmed by the fluorescence-based assay. The improved NMR spectral quality and the retained functional activity of FNT-CB support the feasibility of further structural and functional studies targeted at the anti-inflammatory drug development.

Regulation of different human NFAT isoforms by neuronal activity.

Nuclear factor of activated T-cells (NFAT) is a family of transcription factors comprising four calcium-regulated members: NFATc1, NFATc2, NFATc3, and NFATc4. Upon activation by the calcium-dependent phosphatase calcineurin (CaN), NFATs translocate from cytosol to the nucleus and regulate their target genes, which in the nervous system are involved in axon growth, synaptic plasticity, and neuronal survival. We have shown previously that there are a number of different splice variants of NFAT genes expressed in the brain. Here, we studied the subcellular localizations and transactivation capacities of alternative human NFAT isoforms in rat primary cortical or hippocampal neurons in response to membrane depolarization and compared the induced transactivation levels in neurons to those obtained from HEK293 cells in response to calcium signaling. We confirm that in neurons the translocation to the nucleus of all NFAT isoforms is reliant on the activity of CaN. However, our results suggest that both the regulation of subcellular localization and transcriptional activity of NFAT proteins in neurons is isoform specific. We show that in primary hippocampal neurons NFATc2 isoforms have very fast translocation kinetics, whereas NFATc4 isoforms translocate relatively slowly to the nucleus. Moreover, we demonstrate that the strongest transcriptional activators in HEK293 cells are NFATc1 and NFATc3, but in neurons NFATc3 and NFATc4 lead to the highest induction, and NFATc2 and NFATc1 display isoform-specific transcription activation capacities. Altogether, our results indicate that the effects of calcium signaling on the action of NFAT proteins are isoform-specific and can differ between cell types. We show that the effects of calcium signaling on the action of NFAT proteins are isoform-specific and differ between cell types. Although nuclear localization of all NFAT isoforms in neurons requires calcineurin, the subcellular distributions, neuronal activity-induced nuclear translocation extent and kinetics, and transcription activation capacities of alternative NFAT proteins vary.

Can Nup88 expression be associated with atypical endometrial hyperplasia and endometrial cancer? A preliminary study.

BACKGROUND: Nup88 is overexpressed in a number of types of carcinomas and is associated with myometrial invasion, but its exact expression pattern in endometrial cancer and premalignant lesions is unknown. AIMS: To evaluate the role of Nup88 in endometrial cancers and atypical endometrial hyperplasia and its clinicopathological significance. METHODS: Nup88 expression was examined by immunohistochemistry in samples from 104 endometrial cancers, 21 atypical endometrial hyperplasia lesions, and 40 normal endometria. All samples were from patients who underwent surgery at the First Hospital of Hebei Medical University (Shijiazhuang, China) between April 2006 and December 2009. Nup88 expression was compared between the groups and associations were assessed between Nup88 and clinicopathological characteristics of the subjects. RESULTS: Nup88 expression in cancer (76% of samples) and atypical hyperplasia (91%) was significantly higher compared to normal endometrium (33%, both P<0.001), but there was no significant difference between endometrial cancer and atypical hyperplasia (P=0.237). The expression of Nup88 increased significantly with increasing exposure time to estrogen (P=0.033). CONCLUSIONS: Nup88 may be related to the occurrence of endometrial cancers and premalignant lesions. Nup88 might be a useful biomarker for pre-malignant lesions and early-stage endometrial cancer.

Increased hepatic receptor interacting protein kinase 3 expression due to impaired proteasomal functions contributes to alcohol-induced steatosis and liver injury.

Chronic alcohol exposure increased hepatic receptor-interacting protein kinase (RIP) 3 expression and necroptosis in the liver but its mechanisms are unclear. In the present study, we demonstrated that chronic alcohol feeding plus binge (Gao-binge) increased RIP3 but not RIP1 protein levels in mouse livers. RIP3 knockout mice had decreased serum alanine amino transferase activity and hepatic steatosis but had no effect on hepatic neutrophil infiltration compared with wild type mice after Gao-binge alcohol treatment. The hepatic mRNA levels of RIP3 did not change between Gao-binge and control mice, suggesting that alcohol-induced hepatic RIP3 proteins are regulated at the posttranslational level. We found that Gao-binge treatment decreased the levels of proteasome subunit alpha type-2 (PSMA2) and proteasome 26S subunit, ATPase 1 (PSMC1) and impaired hepatic proteasome function. Pharmacological or genetic inhibition of proteasome resulted in the accumulation of RIP3 in mouse livers. More importantly, human alcoholics had decreased expression of PSMA2 and PSMC1 but increased protein levels of RIP3 compared with healthy human livers. Moreover, pharmacological inhibition of RIP1 decreased Gao-binge-induced hepatic inflammation, neutrophil infiltration and NF-κB subunit (p65) nuclear translocation but failed to protect against steatosis and liver injury induced by Gao-binge alcohol. In conclusion, results from this study suggest that impaired hepatic proteasome function by alcohol exposure may contribute to hepatic accumulation of RIP3 resulting in necroptosis and steatosis while RIP1 kinase activity is important for alcohol-induced inflammation.

Proteomic Profiling of Neuroblastoma Cells Adhesion on Hyaluronic Acid-Based Surface for Neural Tissue Engineering.

The microenvironment of neuron cells plays a crucial role in regulating neural development and regeneration. Hyaluronic acid (HA) biomaterial has been applied in a wide range of medical and biological fields and plays important roles in neural regeneration. PC12 cells have been reported to be capable of endogenous NGF synthesis and secretion. The purpose of this research was to assess the effect of HA biomaterial combining with PC12 cells conditioned media (PC12 CM) in neural regeneration. Using SH-SY5Y cells as an experimental model, we found that supporting with PC12 CM enhanced HA function in SH-SY5Y cell proliferation and adhesion. Through RP-nano-UPLC-ESI-MS/MS analyses, we identified increased expression of HSP60 and RanBP2 in SH-SY5Y cells grown on HA-modified surface with cotreatment of PC12 CM. Moreover, we also identified factors that were secreted from PC12 cells and may promote SH-SY5Y cell proliferation and adhesion. Here, we proposed a biomaterial surface enriched with neurotrophic factors for nerve regeneration application.

Nucleoporin 62 and Ca(2+)/calmodulin dependent kinase kinase 2 regulate androgen receptor activity in castrate resistant prostate cancer cells.

BACKGROUND: Re-activation of the transcriptional activity of the androgen receptor (AR) is an important factor mediating progression from androgen-responsive to castrate-resistant prostate cancer (CRPC). However, the mechanisms regulating AR activity in CRPC remain incompletely understood. Ca(2+) /calmodulin-dependent kinase kinase (CaMKK) 2 was previously shown to regulate AR activity in androgen-responsive prostate cancer cells. Our objective was to further explore the basis of this regulation in CRPC cells. METHODS: The abundance of CaMKK2 in nuclear fractions of androgen-responsive prostate cancer and CRPC, cells were determined by subcellular fractionation and Western blotting. CaMKK2 association with nuclear pore complexes (NPCs) and nucleoporins (Nups) including Nup62, were imaged by structured illumination and super-resolution fluorescence microscopy and co-immunoprecipitation, respectively. The abundance and subcellular localization of CaMKK2 and Nup62 in human clinical specimens of prostate cancer was visualized by immunohistochemistry. The role of Nups in the growth and viability of CRPC cells was assessed by RNA interference and cell counting. The involvement of CaMKK2 and Nup62 in regulating AR transcriptional activity was addressed by RNA interference, chromatin immunoprecipitation, androgen response element reporter assay, and Western blotting. RESULTS: CaMKK2 was expressed at higher levels in the nuclear fraction of CPRC C4-2 cells, than in that of androgen-responsive LNCaP cells. In C4-2 cells, CaMKK2 associated with NPCs of the nuclear envelope and physically interacted with Nup62. CaMKK2 and Nup62 demonstrated pronounced, and similar increases in both expression and perinuclear/nuclear localization in human clinical specimens of advanced prostate cancer relative to normal prostate. Knockdown of Nup62, but not of Nups, 98 or 88, reduced growth and viability of C4-2 cells. Knockdown of Nup62 produced a greater reduction of the growth and viability of C4-2 cells than of non-neoplastic RWPE-1 prostatic cells. Nup62, CaMKK2, and the AR were recruited to androgen response elements of the AR target genes, prostate specific antigen, and transmembrane protease, serine 2. Knockdown of CaMKK2 and Nup62 reduced prostate specific antigen expression and AR transcriptional activity driven by androgen response elements from the prostate-specific probasin gene promoter. CONCLUSION: Nup62 and CaMKK2 are required for optimal AR transcriptional activity and a potential mechanism for AR re-activation in CRPC.

Reduction of Saccharomyces cerevisiae Pom34 protein level by SESA network is related to membrane lipid composition.

Various pathways block initiation of translation of the bulk of mRNAs in response to membrane stress, amino acid starvation and unfolded proteins. In contrast, SESA, a network of proteins comprising Smy2, Eap1, Scp160 and Asc1, is a novel inhibitor of translation initiation of specific mRNAs. SESA binds POM34 mRNA in response to failure in spindle pole body (SPB) duplication process and inhibits its initiation of translation. We herein report that Pom34 protein level is reduced also in cells with altered membrane lipid composition upon treatment with various chemicals and show that SESA-induced downregulation of Pom34 is crucial for viability of cells with a disturbed nuclear envelope. Thus, we propose that SESA's action in SPB duplication process is dependent on the alteration of membrane lipid composition to facilitate the insertion process.

Structural characterization of altered nucleoporin Nup153 expression in human cells by thin-section electron microscopy.

Nuclear pore complexes (NPCs) span the 2 membranes of the nuclear envelope (NE) and facilitate nucleocytoplasmic exchange of macromolecules. NPCs have a roughly tripartite structural organization with the so-called nuclear basket emanating from the NPC scaffold into the nucleoplasm. The nuclear basket is composed of the 3 nucleoporins Nup153, Nup50, and Tpr, but their specific role for the structural organization of this NPC substructure is, however, not well established. In this study, we have used thin-section transmission electron microscopy to determine the structural consequences of altering the expression of Nup153 in human cells. We show that the assembly and integrity of the nuclear basket is not affected by Nup153 depletion, whereas its integrity is perturbed in cells expressing high concentrations of the zinc-finger domain of Nup153. Moreover, even mild over-expression of Nup153 is coinciding with massive changes in nuclear organization and it is the excess of the zinc-finger domain of Nup153 that is sufficient to induce these rearrangements. Our data indicate a central function of Nup153 in the organization of the nucleus, not only at the periphery, but throughout the entire nuclear interior.