Arsenic distribution and partitioning in multiple media in a typical catchment in the Qinghai-Tibetan plateau: A comparison between freshwater and saltwater lakes

Arsenic (As) has been widely detected in surface media on the Qinghai-Tibetan Plateau (QTP); however, the differences in the As distribution and partitioning characteristics between freshwater and saltwater lakes remain poorly understood. To determine the distribution and partitioning characteristics of As, multimedia environmental samples were collected from a typical small watershed consisting of a river, wetland, and both freshwater and saltwater lakes on the QTP. Results showed that freshwater systems, represented by Hurleg Lake, were high in particulate arsenic (PAs) and low in dissolved arsenic (DAs), whereas the saltwater system represented by Tosen Lake, exhibited the reverse distribution. This discrepancy in As distribution was primarily attributed to evaporation enrichment, competitive adsorption of HCO3- and pH variations, as suggested by correlation analysis and stable isotopic composition of water. In the stratified Tosen Lake, an increasing trend of DAs in the water column was observed, potentially driven by the reductive dissolution of Fe (hydr)oxides and bacterial sulfate reduction in the anoxic bottom hypolimnion. Conversely, Hurleg Lake maintained oxic conditions with stable DAs concentrations. Notably, PAs was elevated in the bottom layer of both lakes, possibly due to uptake/adsorption by biogenic particles, as indicated by high levels of chl.α and suspended particulate matter. These findings offer insights into the potential future impact of climate change on As mobilization/redistribution in arid plateau lakes, with implications for management policies that regulate As pollution.

SOJNMF: Identifying Multidimensional Molecular Regulatory Modules by Sparse Orthogonality-Regularized Joint Non-Negative Matrix Factorization Algorithm

Cancer is not only a very aggressive but also a very diverse disease. Recent advances in high-throughput omics technologies of cancer have enabled biomedical researchers to have more opportunities for studying its multi-level biological regulatory mechanism. However, there are few methods to explore the underlying mechanism of cancer by identifying its multidimensional molecular regulatory modules from the multidimensional omics data of cancer. In this paper, we propose a sparse orthogonality-regularized joint non-negative matrix factorization (SOJNMF) algorithm which can integratively analyze multidimensional omics data. This method can not only identify multidimensional molecular regulatory modules, but reduce the overlap rate of features among the multidimensional modules while ensuring the sparsity of the coefficient matrix after decomposition. Gene expression data, miRNA expression data and gene methylation data of liver cancer are integratively analyzed based on SOJNMF algorithm. Then, we obtain 238 multidimensional molecular regulatory modules. The results of permutation test indicate that different omics features within these modules are significantly correlated in statistics. Meanwhile, the results of functional enrichment analysis show that these multidimensional modules are significantly related to the underlying mechanism of the occurrence and development of liver cancer.

Carbon‑sulfur coupling in a seasonally hypoxic, high-sulfate reservoir in SW China: Evidence from stable CS isotopes and sulfate-reducing bacteria

Anthropogenic input of sulfate (SO₄^2-) in reservoirs may enhance bacterial sulfate reduction (BSR) under seasonally hypoxic conditions in the water column. However, factors that control BSR and its coupling to organic carbon (OC) mineralization in seasonally hypoxic reservoirs remain unclear. The present study elucidates the coupling processes by analyzing the concentrations and isotopic composition of dissolved inorganic carbon (DIC) and sulfur (SO₄^2-, sulfide) species, and the microbial community in water of the Aha reservoir, SW China, which has high SO₄^2- concentration due to the inputs from acid mine drainage about twenty years ago. The water column at two sites in July and October revealed significant thermal stratification. In the hypoxic bottom water, the δ¹³C-DIC decreased while the δ³⁴S-SO₄^2- increased, implying organic carbon mineralization due to BSR. The magnitude of S isotope fractionation (Δ³⁴S, obtained from δ³⁴S_sulfate-δ³⁴S_sulfide) during the process of BSR fell in the range of 3.4‰ to 27.0‰ in July and 21.6‰ to 31.8‰ in October, suggesting a change in the community of sulfate-reducing bacteria (SRB). The relatively low water column stability in October compared to that in July weakened the difference of water chemistry and ultimately affected the SRB diversity. The production of DIC (ΔDIC) scaled a strong positive relationship with the Δ³⁴S in July (p < 0.01), indicating that high OC availability favored the survival of incomplete oxidizers of SRB. However, in October, Δ¹³C-DIC was correlated with the Δ³⁴S in the bottom hypoxic water (p < 0.01), implying that newly degraded OC depleted in ¹³C could favor the dominance of complete oxidizers of SRB which caused greater S isotope fractionation. Moreover, the sulfide supplied by BSR might stimulate the reductive dissolution of Fe and Mn oxides (Fe(O)OH and MnO₂). The present study helps to understand the coupling of C and S in seasonally hypoxic reservoirs characterized by high SO₄^2- concentration.

FSCAM: CAM-Based Feature Selection for Clustering scRNA-seq

Cell type determination based on transcriptome profiles is a key application of single-cell RNA sequencing (scRNA-seq). It is usually achieved through unsupervised clustering. Good feature selection is capable of improving the clustering accuracy and is a crucial component of single-cell clustering pipelines. However, most current single-cell feature selection methods are univariable filter methods ignoring gene dependency. Even the multivariable filter methods developed in recent years only consider "one-to-many" relationship between genes. In this paper, a novel single-cell feature selection method based on convex analysis of mixtures (FSCAM) is proposed, which takes into account "many-to-many" relationship. Compared to the previous "one-to-many" methods, FSCAM selects genes with a combination of relevancy, redundancy and completeness. Pertinent benchmarking is conducted on the real datasets to validate the superiority of FSCAM. Through plugging into the framework of partition around medoids (PAM) clustering, a single-cell clustering algorithm based on FSCAM method (SCC_FSCAM) is further developed. Comparing SCC_FSCAM with existing advanced clustering algorithms, the results show that our algorithm has advantages in both internal criteria (clustering number) and external criteria (adjusted Rand index) and has a good stability.

A network-based matrix factorization framework for ceRNA co-modules recognition of cancer genomic data

With the development of high-throughput technologies, the accumulation of large amounts of multidimensional genomic data provides an excellent opportunity to study the multilevel biological regulatory relationships in cancer. Based on the hypothesis of competitive endogenous ribonucleic acid (RNA) (ceRNA) network, lncRNAs can eliminate the inhibition of microRNAs (miRNAs) on their target genes by binding to intracellular miRNA sites so as to improve the expression level of these target genes. However, previous studies on cancer expression mechanism are mostly based on individual or two-dimensional data, and lack of integration and analysis of various RNA-seq data, making it difficult to verify the complex biological relationships involved. To explore RNA expression patterns and potential molecular mechanisms of cancer, a network-regularized sparse orthogonal-regularized joint non-negative matrix factorization (NSOJNMF) algorithm is proposed, which combines the interaction relations among RNA-seq data in the way of network regularization and effectively prevents multicollinearity through sparse constraints and orthogonal regularization constraints to generate good modular sparse solutions. NSOJNMF algorithm is performed on the datasets of liver cancer and colon cancer, then ceRNA co-modules of them are recognized. The enrichment analysis of these modules shows that >90% of them are closely related to the occurrence and development of cancer. In addition, the ceRNA networks constructed by the ceRNA co-modules not only accurately mine the known correlations of the three RNA molecules but also further discover their potential biological associations, which may contribute to the exploration of the competitive relationships among multiple RNAs and the molecular mechanisms affecting tumor development.

[Quantifying the state of cell differentiation based on the gene networks entropy]

Studies of cellular dynamic processes have shown that cells undergo state changes during dynamic processes, controlled mainly by the expression of genes within the cell. With the development of high-throughput sequencing technologies, the availability of large amounts of gene expression data enables the acquisition of true gene expression information of cells at the single-cell level. However, most existing research methods require the use of information beyond gene expression, thus introducing additional complexity and uncertainty. In addition, the prevalence of dropout events hampers the study of cellular dynamics. To this end, we propose an approach named gene interaction network entropy (GINE) to quantify the state of cell differentiation as a means of studying cellular dynamics. Specifically, by constructing a cell-specific network based on the association between genes through the stability of the network, and defining the GINE, the unstable gene expression data is converted into a relatively stable GINE. This method has no additional complexity or uncertainty, and at the same time circumvents the effects of dropout events to a certain extent, allowing for a more reliable characterization of biological processes such as cell fate. This method was applied to study two single-cell RNA-seq datasets, head and neck squamous cell carcinoma and chronic myeloid leukaemia. The GINE method not only effectively distinguishes malignant cells from benign cells and differentiates between different periods of differentiation, but also effectively reflects the disease efficacy process, demonstrating the potential of using GINE to study cellular dynamics. The method aims to explore the dynamic information at the level of single cell disorganization and thus to study the dynamics of biological system processes. The results of this study may provide scientific recommendations for research on cell differentiation, tracking cancer development, and the process of disease response to drugs.

Microbial controls on heavy metals and nutrients simultaneous release in a seasonally stratified reservoir

The eutrophication of reservoirs can change the physicochemical parameters of water, thus affecting the migration and transformation of heavy metals. At present, there is insufficient research on the coupling mechanisms between nutrients and heavy metals, especially between heavy metals in suspended particles. In this paper, spatial and temporal distribution characteristics of nutrients dissolved heavy metals, and heavy metals in suspended particles were analyzed in a seasonally stratified reservoir. Combined with the nitrogen and phosphorus biogeochemical process, the coupling mechanisms between heavy metals and nutrients were discussed. The results showed that the Aha Reservoir had temperature and dissolved oxygen stratification in April and July. The reduction and dissolution of Fe and Mn oxide/hydroxide and the resuspension of sediments might result in a simultaneous increase in the concentrations of nutrients, dissolved heavy metals and heavy metals in suspended particles in hypolimnion in July and October. In the presence of dissimilatory iron-reducing bacteria (DRIB), the dissolution of iron-bound phosphorus in sediments and suspended particulate matter (SPM) might lead to the simultaneous release of iron and phosphorus into the water. The dissolution of metal sulfides in the sediments and SPM under the action of dissimilatory nitrate reduction to ammonium (DNRA) bacteria might lead to the simultaneous release of ammonia nitrogen and heavy metals into the water. Due to the coupling between nitrogen and phosphorus and heavy metals, seasonal stratified reservoir may face the risk of periodic simultaneous pollution of eutrophication and heavy metals in summer and autumn. This research provides theoretical support for the treatment of heavy metal and eutrophication combined pollution in karst areas.

Identifying Critical States of Hepatocellular Carcinoma Based on Single- Sample Dynamic Network Biomarkers Combined with Simulated Annealing Algorithm

Background:

Hepatocellular Carcinoma (HCC) is one of the most common malignant tumors. Due to the insidious onset and poor prognosis, most patients have reached the advanced stage at the time of diagnosis.

Objective:

Studies have shown that Dynamic Network Biomarkers (DNB) can effectively identify the critical state of complex diseases such as HCC from normal state to disease state. Therefore, it is very important to detect DNB efficiently and reliably.

Methods:

This paper selects a dataset containing eight HCC disease states. First, an individual-specific network is constructed for each sample and features are extracted. In the context of this network, a simulated annealing algorithm is used to search for potential dynamic network biomarker modules, and the evolution of HCC is determined.

Results:

In fact, in the period of Low-Grade Dysplasia (LGD) and High-Grade Dysplasia (HGD), DNB sends an indicative warning signal, which means that liver dysplasia is a very important critical state in the development of HCC disease. Compared with landscape dynamic network biomarkers method (LDNB), our method can not only describe the statistical characteristics of each disease state, but also yield better results including getting more DNBs enriched in HCC related pathways.

Conclusion:

The results of this study may be of great significance to the prevention and early diagnosis of HCC.

Effects of EFNA1 on cell phenotype and prognosis of esophageal carcinoma

Background

To investigate the expression and clinical significance of EFNA1 in broad-spectrum tumors, and to evaluate its relationship with prognosis and biological functions of esophageal carcinoma (ESCA).

Methods

EFNA1 expression in various cancers was analyzed according to the data in the TCGA database. The clinical data were integrated, to analyze the relationship with ESCA clinical parameters and prognosis, and EFNA1 expression in ESCA tissue samples was detected by immunohistochemistry (IHC). Based on bioinformatics, the functional background of EFNA1 overexpression was analyzed. EFNA1 knockout cell model was established by EFNA1-shRNA transfecting ESCA cells, and the effect of knocking down EFNA1 on the proliferation of ESCA cells was detected by MTT.

Results

Among 7563 samples from TCGA, the EFNA1 gene highly expressed in 15 samples with common cancers and endangered the prognosis of patients with tumors. Its overexpression in ESCA and its influence on the prognosis were most significant. EFNA1 expression in 80 samples with ESCA and their paired samples was tested by IHC to verify its high expression (paired t test, P < 0.001) in ESCA tissues. It was found that EFNA1 expression was related to clinical factors (TNM staging, P = 0.031; lymph node metastasis, P = 0.043; infiltration, P = 0.016). Meanwhile, EFNA1 was found to be an independent risk factor based on the COX multi-factor analysis. And to further explore the importance of EFNA1 in tumors, EC-9706 and ECA109 cells were screened from 8 ESCA-related cell lines to build EFNA1 knockdown cell models. The results showed that EFNA1 knockdown significantly inhibited the proliferation of tumor cells (P < 0.05). In terms of molecular mechanism, EFNA1 related genes were significantly enriched in the proliferative pathway according to the pathway enrichment analysis. It was found that knocking down EFNA1 did inhibit cell proliferation based on cell experiments.

Conclusions

EFNA1 overexpression in ESCA tissue is related to the prognosis of patients. Knocking down EFNA1 can significantly inhibit the proliferation of ESCA cells.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12957-021-02362-8.

Effects of quercetin on cadmium-induced toxicity in rat urine using metabonomics techniques

This study aimed to analyse the protective effects of quercetin on the toxicity of cadmium (Cd) using metabonomics techniques. Sixty male Sprague-Dawley rats were randomly divided into six groups (n = 10): control group (C), low-dose quercetin-treated group (Q1; 10 mg/kg bw/day), high-dose quercetin-treated group (Q2; 50 mg/kg bw/day), Cd-treated group (D; 4.89 mg/kg bw/day), low-dose quercetin plus Cd-treated group (DQ1) and high-dose quercetin plus Cd-treated group (DQ2). The rats continuously received quercetin and Cd via gavage and drinking water for 12 weeks, respectively. The rat urine samples were collected for metabonomics analysis. Finally, 10 metabolites were identified via the metabonomics profiles of the rat urine samples. Compared with the control group, the intensities of taurine, phosphocreatine, l-carnitine and uric acid were significantly decreased (p < 0.01) and those of LysoPC (18: 2 (9Z, 12Z)), guanidinosuccinic acid, dopamine, 2,5,7,8-tetramethyl-2(2'-carboxyethyl)-6-hydroxychroman and allantoic acid were significantly increased (p < 0.01) in the Cd-treated group. However, the intensities of the aforementioned metabolites had restorative changes in the high-dose quercetin plus Cd-treated groups unlike those in Cd-treated group (p < 0.01 or p < 0.05). Results indicated that quercetin exerts protective effects on Cd-induced toxicity by regulating energy and lipid metabolism, enhancing the antioxidant defence system and protecting liver and kidney function and so on.

[An interlaboratory comparison study on the detection of RUNX1-RUNX1T1 fusion transcript levels and WT1 transcript levels]

Objective: To investigate the current status and real performance of the detection of RUNX1-RUNX1T1 fusion transcript levels and WT1 transcript levels in China through interlaboratory comparison. Methods: Peking University People's Hospital (PKUPH) prepared the samples for comparison. That is, the fresh RUNX1-RUNX1T1 positive (+) bone morrow nucleated cells were serially diluted with RUNX1-RUNX1T1 negative (-) nucleated cells from different patients. Totally 23 sets with 14 different samples per set were prepared. TRIzol reagent was added in each tube and thoroughly mixed with cells for homogenization. Each laboratory simultaneously tested RUNX1-RUNX1T1 and WT1 transcript levels of one set of samples by real-time quantitative PCR method. All transcript levels were reported as the percentage of RUNX1-RUNX1T1 or WT1 transcript copies/ABL copies. Spearman correlation coefficient between the reported transcript levels of each participated laboratory and those of PKUPH was calculated. Results: ①RUNX1-RUNX1T1 comparison: 9 samples were (+) and 5 were (-) , the false negative and positive rates of the 20 participated laboratories were 0 (0/180) and 5% (5/100) , respectively. The reported transcript levels of all 9 positive samples were different among laboratories. The median reported transcript levels of 9 positive samples were from 0.060% to 176.7%, which covered 3.5-log. The ratios of each sample's highest to the lowest reported transcript levels were from 5.5 to 12.3 (one result which obviously deviated from other laboratories' results was not included) , 85% (17/20) of the laboratories had correlation coefficient ≥0.98. ②WT1 comparison: The median reported transcript levels of all 14 samples were from 0.17% to 67.6%, which covered 2.6-log. The ratios of each sample's highest to the lowest reported transcript levels were from 5.3-13.7, 62% (13/21) of the laboratories had correlation coefficient ≥0.98. ③ The relative relationship of the reported RUNX1-RUNX1T1 transcript levels between the participants and PKUPH was not always consistent with that of WT1 transcript levels. Both RUNX1-RUNX1T1 and WT1 transcript levels from 2 and 7 laboratories were individually lower than and higher than those of PKUPH, whereas for the rest 11 laboratories, one transcript level was higher than and the other was lower than that of PKUPH. Conclusion: The reported RUNX1-RUNX1T1 and WT1 transcript levels were different among laboratories for the same sample. Most of the participated laboratories reported highly consistent result with that of PKUPH. The relationship between laboratories of the different transcript levels may not be the same.

[A novel VSX1 gene mutation identified in a sporadic keratoconus patient from China]

Objective: To investigate the possibility of the visual system homeobox 1 (VSX1) gene as a candidate susceptibility gene for Chinese patients with sporadic keratoconus, and to identify sequence variants of the VSX1 gene in such patients. Methods: Cross-sectional study. Genomic DNA was extracted from the leukocytes in the peripheral venous blood of 50 patients with sporadic keratoconus and 50 control subjects without this ocular disorder. Five exons and the intron-exon splicing of the VSX1 gene were amplified by polymerase chain reaction (PCR). The PCR products were directly sequenced and compared to the GeneBank database to find mutations. Bioinformatics analysis was done to predict the influence of these mutations on proteins. Results: One novel missense heterozygous mutation (p.R131P) was found in exon 1 of the VSX1 gene in one keratoconus patient. Another heterozygous mutation (p.G160V) in exon 2 was found in two keratoconus patients. These mutations were not detected in the control subjects. Bioinformatics analysis predicted that the p.R131P mutation may not cause a pathogenic change, but the p.G160V mutation might be functionally deleterious. In intron 3 of the VSX1 gene, the nucleotide substitution of g.8326G>A was detected to be heterozygous in 3 cases of sporadic keratoconus and 4 cases of control and homozygous in 2 cases of sporadic keratoconus and 1 case of control. The variation of g.8326G>A belonged to a single polymorphism change of the VSX1 gene. Conclusions: The p.R131P detected in this study is a novel mutation of the VSX1 gene. Sequence variants of the VSX1 gene were identified for the first time in Chinese patients with sporadic keratoconus, but their precise role in disease causation requires further investigations. (Chin J Ophthalmol, 2018, 54: 212-217).

[Reproductive and developmental toxicity of 2- (2H-1, 2, 3-benzotriazol-2-yl) -4-methyl-6- (2-methylpropen-2-yl) phenol in mice: an experimental study]

Objective: To investigate the reproductive and developmental toxicity of 2- (2H-1, 2, 3-benzotriazol-2-yl) -4-methyl-6- (2-methylpropen-2-yl) phenol in mice and to provide a basis for its risk assessment. Methods: The reproductive and developmental toxicity of 2- (2H-1, 2, 3-benzotriazol-2-yl) -4-methyl-6- (2-methylpropen-2-yl) phenol was tested using the screening method of chemicals with reproductive and developmental toxicity in "Chemical Testing Method" (SEPA). After five days of adaptive feeding, 120 specific pathogen-free healthy Kunming mice (male/female ratio=1:1) were orally administered 0 (control) , 146, 292, and 584 mg/kg 2- (2H-1, 2, 3-benzotriazol-2-yl) -4-methyl-6- (2-methylpropen-2-yl) phenol for two weeks. One male mouse was mated with one female mouse in a single cage. The day on which a vaginal plug was observed was defined as gestation day 0 (GD0). The exposure for female mice was sustained to four days postpartum and the exposure for male mice was sustained for two weeks after mating. The body weight, food intake, body length, tail length, and sex ratio were recorded and the reproductive index was calculated. The reproductive organs were weighed and subjected to histopathological examination. Results: The 584 mg/kg group had significantly lower body weight at weeks 5 and 6 and food intake at week 6 in male mice, uterus weight and uterus/body weight ratio in female mice, and body weight, body length, and tail length on day 0 in offspring compared with the control group (all P<0.05). The 292 mg/kg group had significantly lower testis weight of male mice and food intake of female mice at gestational week 2 than the control group (both P<0.05). The 146 mg/kg group had significantly lower food intake of female mice at gestational week 2 than the control group (P<0.05) . Conclusion: For male and female Kunming mice, the no observed adverse effect levels of 2- (2H-1, 2, 3, -benzotriazol-2-yl) -4-methyl-6- (2-methylpropen-2-yl) phenol are both 146 mg/kg.

Suppression of hepatoma tumor growth by systemic administration of the phytotoxin gelonin driven by the survivin promoter

Hepatocellular carcinoma (HCC) is one of the most common types of cancer worldwide. However, there is currently no effective therapy strategy in the clinical practice. Recombinant phytotoxin gelonin fused to other factors have been used to treat different cancers. But there have been no reports of gelonin gene therapy. In this study, we have constructed a recombinant plasmid which contained a tumor-specific survivin promoter to drive phytotoxin gelonin (pSur-Gel). And the cytotoxicity effects of pSur-Gel in HCC were also validated both in vitro and in vivo. The expression level of survivin was detected in different liver cancer cell lines and normal liver cell lines by western blot analysis, and a survivin promoter-driven green fluorescent protein (GFP) expression vectors (pSur-GFP) was also tested in liver cancer cell line HepG2 and normal liver cell line LO2. Moreover, phytotoxin gelonin expression experiment and cytotoxicity experiment of pSur-Gel was performed in HepG2 cells and LO2 cells in vitro. Furthermore, anti-tumor effect of pSur-Gel against HepG2 xenografts and toxicity of this gene were evaluated in the mice model. Finally, LDH release assay, apoptosis assay and immunoblot analyse LC3 conversion (LC3-I to LC3-II) were tested. We found that the expression of survivin protein was higher in liver cancer cell lines compared with the normal liver cells. Further study showed that the pSur-GFP and pSur-Gel was expressed specially in liver cancer cell other than in normal liver cells. pSur-Gel plasmid could effectively inhibit the proliferation of liver cancer cells (*P<0.05), and significantly repress the growth of HepG2 xenografts via intravenous in vivo (*P<0.05). Otherwise, compared to cytomegalovirus promoter-driven gelonin expression vectors (pCMV-Gel), no significantly systemic toxicity or organ injuries had been observed in pSur-Gel treated mice. Further studies revealed that the phytotoxin gelonin induced cell death might be mediated by apoptosis and the damage of cell membrane. Taken together, treating hepatocellular carcinoma with the pSur-Gel may be a novel and interesting cancer gene therapy protocol and is worthy of further development for future clinical trials.

KEYWORDS

liver cancer, gelonin, survivin promoter, gene therapy.

Gate-voltage control of chemical potential and weak antilocalization in Bi₂Se₃

We report that Bi₂Se₃ thin films can be epitaxially grown on SrTiO₃ substrates, which allow for very large tunablity in carrier density with a back gate. The observed low field magnetoconductivity due to weak antilocalization (WAL) has a very weak gate-voltage dependence unless the electron density is reduced to very low values. Such a transition in WAL is correlated with unusual changes in longitudinal and Hall resistivities. Our results suggest a much suppressed bulk conductivity at large negative gate voltages and a possible role of surface states in the WAL phenomena.

Induction of tumoricidal activity in mouse peritoneal macrophages by ginseng polysaccharide

This study examined the effects of ginseng polysaccharide (GPS) on mouse peritoneal macrophage (PM)-mediated cytotoxicity towards K562, HL-60, or KG1alpha cells. GPS had no direct effect on killing of tumor cells. However, when mouse PMs were treated with GPS, cytotoxic activity against K562, HL-60, or KG1alpha cells was significantly induced. In addition, phagocytic activity was enhanced in GPS-treated mouse PMs compared to the control. The expressions of CD(68), ACP and alpha-ANE in mouse PMs were increased by the treatment with GPS. Moreover, the levels of cytokines, including tumor necrosis factor-alpha (TNF-alpha), interleukin-1 (IL-1), IL-6 were increased and the production of nitric oxide (NO) was enhanced. Taken together, these results suggest that GPS possess a potent antitumor activity by stimulating macrophage and a potentiality as an immunomodulator against diseases such as cancer.

Total saponins of Panax ginseng (TSPG) promote erythroid differentiation of human CD34+ cells via EpoR-mediated JAK2/STAT5 signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Total saponins of Panax ginseng (TSPG), main constituents extracted from Panax ginseng, a highly valued traditional Chinese medicine, have been shown to be an effective agent on hematopoiesis.

OBJECTIVE

To investigate the effect and mechanism underlying in which TSPG promote human CD34(+) hematopoietic stem and progenitor cells to differentiate into erythroid-lineage cells.

MATERIALS AND METHODS

The effect of TSPG on erythroid differentiation of purified CD34(+) cells derived from umbilical cord blood (UCB) was determined by methylcellulose assay system and colorimetry for hemoglobin content. The changes of EpoR expression in umbilical cord blood mononuclear cells (UCB-MNCs) and purified CD34(+) cells were detected with Western blotting and flow cytometry, respectively, and observed under laser scanning confocal microscope (LSCM). RT-PCR was performed to examine EpoR mRNA expression in CD34(+) cells. The effects of TSPG-pretreatment on Epo-induced JAK(2) and STAT(5) tyrosine phosphorylation were analyzed by immunoprecipitation.

RESULTS

The addition of TSPG (20-70 mg/L) increased the colony formation rate of BFU-E. TSPG (50 mg/L) alone used significantly increased the hemoglobin content, the addition of AG490 evidently reduced TSPG-induced elevation of hemoglobin content. TSPG increased the expression of EpoR on the surface membrane of CD34(+) cells but did not change the expression of EpoR in total UCB-MNCs. TSPG also increased the expression of EpoR mRNA in CD34(+) cells. TSPG markedly enhanced Epo-induced tyrosine phosphorylation of JAK(2) and STAT(5) in UCB-MNCs.

CONCLUSION

These findings suggest that TSPG may enhance the erythroid differentiation of hematopoietic stem and progenitor cells via Epo/EpoR-mediated JAK(2)/STAT(5) signaling pathway.

RNA export mediated by tap involves NXT1-dependent interactions with the nuclear pore complex

Nuclear export of ribonucleoprotein complexes requires cis-acting signals and recognition by receptors that mediate translocation through the nuclear pore complex. Translocation is likely to involve a series of physical interactions between the ribonucleoprotein complex and nucleoporins within the nuclear pore complex. Here, we have characterized the function of NXT1 in the context of the Tap-dependent RNA export pathway. Tap has been implicated in the nuclear export of RNA transcripts derived from Mason-Pfizer monkey virus that contain the constitutive transport element. We demonstrate that NXT1 stimulates binding of a Tap-RNA complex to nucleoporins in vitro, and we provide mutational analysis that shows these interactions are necessary for nuclear export of an intron-containing viral mRNA in vivo. Tap contains separate domains for binding to nucleoporins and NXT1, both of which are critical for its export function. RNA export is mediated by a heterodimer of Tap and NXT1, and the function of NXT1 on this pathway is to regulate the affinity of the Tap-RNA complex for nucleoporins within the nuclear pore complex. We propose that NXT1-dependent binding of the Tap-RNA complex to the nucleoporin p62, which we have reconstituted in vitro using recombinant proteins, represents a single step of the translocation reaction.

[The Raman spectra study on crystal-octadecyl hydrogen succinate crystal]

Raman spectra of crystal-octadecyl hydrogen succinate (OHS), whose geometric disposition of the experiment has y(zx)y, y(zz)y, and y(xz)y,y(xx)y respectively, have been recorded and analyzed with the purpose of understanding the structure of OHS crystal. It shows that some of the Raman-active modes of alkyl chain appear polarization. The analysis for crystal structure indicates that the molecular of OHS arrange in layers along [100] and [001] by the mode of dimers, and the molecular layers of chain pile up along [010]. The other groups of OHS corresponding Raman vibration peaks have been analyzed as well.

[The Raman spectra study on crystal-octadecyl hydrogen maleate (OHM)]

Raman spectra of crystal-octadecyl hydrogen maleate (OHM), whose geometric disposition of the experiment has y (zx) y y(zz)y, and y(xz)y, y(xx)y respectively, have been recorded and analyzed with the purpose of understanding the structure of OHM crystal. It shows that some of the Raman-active modes of alkyl chain appear polarization. The analysis for crystal structure indicates that the molecular of OHM arrange in layers along [100] and [001] by the mode of dimers, and the molecular layers of chain pile up along [010]. The other groups of OHM corresponding Raman vibration peaks have been analysed as well.

[The relationship between clinical types of postinfarction angina and stenosis of ischemia-related artery]

OBJECTIVE

To approach the pathogenesis of postinfarction angina and set up its treatment guidelines.

METHODS

67 patients with postinfarction angina undergoing coronary angiography during the hospitalization were studied.

RESULTS

(1) According to the clinical classification of angina pectoris, spontaneous angina is the most common type (43.9%); mixed angina is second (25.7%), effort angina and variant angina are relatively low frequency (16.7% & 13.6%). (2) Stenosis >or= 90% in the ischemia-related artery accounted for the anginal symptoms constituted 100%, 82.8%, 72.7% and 44.4% of the cases with mixed angina, spontaneous angina, effort angina and variant angina respectively. (3) Postinfarction angina caused by non infarction-related artery was relatively less frequent (8.9%).

CONCLUSIONS

Severe residual stenosis of infarction-related artery is the main pathologic factor on the pathogenesis of postinfarction angina, so early interventional therapy or bypass surgery should be taken.

Nup50, a nucleoplasmically oriented nucleoporin with a role in nuclear protein export

We present here a detailed analysis of a rat polypeptide termed Nup50 (formerly NPAP60) that was previously found to be associated with the nuclear pore complex (F. Fan et al., Genomics 40:444-453, 1997). We have found that Nup50 (and/or a related 70-kDa polypeptide) is present in numerous rat cells and tissues. By immunofluorescence microscopy, Nup50 was found to be highly concentrated at the nuclear envelope of rat liver nuclei, whereas in cultured NRK cells it also is abundant in intranuclear regions. On the basis of immunogold electron microscopy of both rat liver nuclear envelopes and NRK cells, we determined that Nup50 is specifically localized in the nucleoplasmic fibrils of the pore complex. Microinjection of anti-Nup50 antibodies into the nucleus of NRK cells resulted in strong inhibition of nuclear export of a protein containing a leucine-rich nuclear export sequence, whereas nuclear import of a protein containing a classical nuclear localization sequence was unaffected. Correspondingly, CRM1, the export receptor for leucine-rich export sequences, directly bound to a fragment of Nup50 in vitro, whereas several other import and export receptors did not significantly interact with this fragment. Taken together, our data indicate that Nup50 has a direct role in nuclear protein export and probably serves as a binding site on the nuclear side of the pore complex for export receptor-cargo complexes.

Regulation of adenovirus membrane penetration by the cytoplasmic tail of integrin beta5

Adenovirus (Ad) cell entry involves sequential interactions with host cell receptors that mediate attachment (CAR), internalization (alphavbeta3 and alphavbeta5), and penetration (alphavbeta5) of the endosomal membrane. These events allow the virus to deliver its genome to the nucleus. While integrins alphavbeta3 and alphavbeta5 both promote Ad internalization into cells, integrin alphavbeta5 selectively facilitates Ad-mediated membrane permeabilization and endosome rupture. In the experiments reported herein, we demonstrate that the intracellular domain of the integrin beta5 subunit specifically regulates Ad-mediated membrane permeabilization and gene delivery. CS-1 melanoma cells expressing a truncated integrin beta5 or a chimeric (beta5-beta3) cytoplasmic tail (CT) supported normal levels of Ad endocytosis but had reduced Ad-mediated gene delivery and membrane permeabilization relative to cells expressing a wild-type integrin beta5. Thin-section electron microscopy revealed that virion particles were capable of being endocytosed into cells expressing a truncated beta5CT, but they failed to escape cytoplasmic vesicles and translocate to the nucleus. Site-specific mutagenesis studies suggest that a C-terminal TVD motif in the beta5CT plays a major role in Ad membrane penetration.

Nuclear import of adenovirus DNA in vitro involves the nuclear protein import pathway and hsc70

Adenovirus, a respiratory virus with a double-stranded DNA genome, replicates in the nuclei of mammalian cells. We have developed a cytosol-dependent in vitro assay utilizing adenovirus nucleocapsids to examine the requirements for adenovirus docking to the nuclear pore complex and for DNA import into the nucleus. Our assay reveals that adenovirus DNA import is blocked by a competitive excess of classical protein nuclear localization sequences and other inhibitors of nuclear protein import and indicates that this process is dependent on hsc70. Previous work revealed that the hexon (coat) protein of adenovirus is the only major protein on the surface of the adenovirus nucleocapsid that docks at the nuclear pore complex. This, together with our finding that in vitro nuclear import of hexon is inhibited by an excess of classical nuclear localization sequences, suggests a role for the hexon protein in adenovirus DNA import. However, recombinant transport factors that are sufficient for hexon import in permeabilized cells do not support DNA import, indicating that there are other as yet unidentified factors required for this process.

[Measurement of boundary line of urinary bladder and peritoneum in abdominal wall and the application in performing cesarean section with urinary bladder reversal method]

OBJECTIVE

To provide the basic research data and clinical application in performing extraperitoneal cesarean section (CS) with urinary bladder reversal method.

METHODS

The position and the surface projection of the vesico-peritoneal fold and the apex of the urinary bladder were measured in 107 cases of term pregnant women (37-42 weeks, aged 20-40).

RESULTS

The distance from the bladder apex to the umbilicus and to the symphysis pubis were (14.1 +/- 3.4) cm and (6.8 +/- 1.4) cm respectively, while from the utero-vesical pouch to umbilicus and symphysis pubis were (15.8 +/- 3.9) cm and (4.9 +/- 1.5) cm respectively. During late pregnancy the projection of bladder apex was located at the point between the middle and the lower 1/3 of the line from umbilicus to symphysis pubis; while the utero-vesical pouch was located at the point between upper 3/4 and the lower 1/4 of the same line. The time interval from the start of operation to the delivery of baby was (14.56 +/- 6.3) min, and the total operation period was (45.5 +/- 9.3) min. The largest baby weighed 5,050 gm and there was no bladder injury.

CONCLUSION

To define the position of vesical peritoneal fold would give benefit to the extraperitoneal CS with bladder reversal method which was performed under direct visualization and could avoid injury of bladder.

A role for RanBP1 in the release of CRM1 from the nuclear pore complex in a terminal step of nuclear export

We recently developed an assay in which nuclear export of the shuttling transcription factor NFAT (nuclear factor of activated T cells) can be reconstituted in permeabilized cells with the GTPase Ran and the nuclear export receptor CRM1. We have now used this assay to identify another export factor. After preincubation of permeabilized cells with a Ran mutant that cannot hydrolyze GTP (RanQ69L), cytosol supports NFAT export, but CRM1 and Ran alone do not. The RanQ69L preincubation leads to accumulation of CRM1 at the cytoplasmic periphery of the nuclear pore complex (NPC) in association with the p62 complex and Can/Nup214. RanGTP-dependent association of CRM1 with these nucleoporins was reconstituted in vitro. By biochemical fractionation and reconstitution, we showed that RanBP1 restores nuclear export after the RanQ69L preincubation. It also stimulates nuclear export in cells that have not been preincubated with RanQ69L. RanBP1 as well as Ran-binding domains of the cytoplasmic nucleoporin RanBP2 promote the release of CRM1 from the NPC. Taken together, our results indicate that RanGTP is important for the targeting of export complexes to the cytoplasmic side of the NPC and that RanBP1 and probably RanBP2 are involved in the dissociation of nuclear export complexes from the NPC in a terminal step of transport.

[Insulin receptor substrate-1 and glucose transporter gene polymorphisms in noninsulin-dependent diabetes mellitus]

OBJECTIVE

To evaluate the role of insulin receptor substrate-1 (IRS-1) and glucose transporter-1 (GLUT1) gene polymorphisms in Chinese patients with noninsulin-dependent diabetes mellitus (NIDDM) and diabetic neophropathy (DN).

METHODS

Aminoacid polymorphism in codon 972 of IRS-1 gene and the polymorphic Xba I site of GLUT1 gene were analyzed by PCR-RFLP in 131 patients with NIDDM and 124 normal subjects. DN was defined as persistent albuminuria and/or impaired renal function, without known cause of renal diseases other than diabetes. Insulin sensitivity index (ISI) and body mass index (BMI) were also calculated.

RESULTS

The distribution of IRS-1 gene polymorphism showed no difference between patients with NIDDM and normal controls. The frequencies of Xba I (+/-) genotype (59% vs. 33%, P < 0.01) and Xba I (-) allele (37% vs. 21%, P < 0.01) were significantly higher in NIDDM patients than in normal subjects. To further explore the linkage of GLUT1 gene polymorphism with DN, we examined the GLUT1 genotype of NIDDM patients with or without renal damage. The frequency of Xba I (+/-) genotype (75% vs. 44%, P < 0.01) and Xba I (-) allele (44% vs. 29%, P < 0.05) was significantly higher in NIDDM patients with diabetic nephropathy than either those without nephropathy or normal subjects. However, there were no significant differences of GLUT1 genotype and allele frequency in NIDDM patients without nephropathy and normal controls. The presence of Xba I (-) allele appeared to have a strong association with the development of diabetic nephropathy. The odds ratio was 1.915, and the 95% confidence interval was 1.044-3.514. The association of Xba I (-) allele of GLUT1 gene with NIDDM partly reflected their close association with DN. Although there was no correlation between the gene polymorphism of GLUT1 and BMI, patients carrying the Xba I (-) allele showed a lower ISI.

CONCLUSION

No association was found between the gene polymorphism of IRS-1 and NIDDM. THe Xba I (-) allele of GLUT1 gene might be taken as a genetic marker of NIDDM with diabetic nephropathy and this genetic susceptibility appears to be associated with the insulin resistance in patients with NIDDM.

RanGTP targets p97 to RanBP2, a filamentous protein localized at the cytoplasmic periphery of the nuclear pore complex

RanBP2, a protein containing FG repeat motifs and four binding sites for the guanosine triphosphatase Ran, is localized at the cytoplasmic periphery of the nuclear pore complex (NPC) and is believed to play a critical role in nuclear protein import. We purified RanBP2 from rat liver nuclear envelopes and examined its structural and biochemical properties. Electron microscopy showed that RanBP2 forms a flexible filamentous molecule with a length of approximately 36 nm, suggesting that it comprises a major portion of the cytoplasmic fibrils implicated in initial binding of import substrates to the NPC. Using in vitro assays, we characterized the ability of RanBP2 to bind p97, a cytosolic factor implicated in the association of the nuclear localization signal receptor with the NPC. We found that RanGTP promotes the binding of p97 to RanBP2, whereas it inhibits the binding of p97 to other FG repeat nucleoporins. These data suggest that RanGTP acts to specifically target p97 to RanBP2, where p97 may support the binding of an nuclear localization signal receptor/substrate complex to RanBP2 in an early step of nuclear import.

Lamin-binding fragment of LAP2 inhibits increase in nuclear volume during the cell cycle and progression into S phase

Lamina-associated polypeptide 2 (LAP2) is an integral membrane protein of the inner nuclear membrane that binds to both lamin B and chromatin and has a putative role in nuclear envelope (NE) organization. We found that microinjection of a recombinant polypeptide comprising the nucleoplasmic domain of rat LAP2 (residues 1-398) into metaphase HeLa cells does not affect the reassembly of transport-competent nuclei containing NEs and lamina, but strongly inhibits nuclear volume increase. This effect appears to be specifically due to lamin binding, because it also is caused by microinjection of the minimal lamin-binding region of LAP2 (residues 298-373) but not by the chromatin-binding domain (residues 1-88). Injection of the lamin-binding region of rat LAP2 into early G1 phase HeLa cells also strongly affects nuclear growth; it almost completely prevents the threefold nuclear volume increase that normally occurs during the ensuing 10 h. Moreover, injection of the fragment during early G1 phase strongly inhibits entry of cells into S phase, whereas injection during S phase has no apparent effect on ongoing DNA replication. Since the lamin-binding fragment of LAP2 most likely acts by inhibiting dynamics of the nuclear lamina, our results suggest that a normal function of LAP2 involves regulation of nuclear lamina growth. These data also suggest that lamina dynamics are required for growth of the NE and for nuclear volume increase during the cell cycle, and that progression into S phase is dependent on the acquisition of a certain nuclear volume.

High levels of the GTPase Ran/TC4 relieve the requirement for nuclear protein transport factor 2

The GTPase Ran/TC4 and the 14-kDa protein nuclear transport factor 2 (NTF2) are two of the cytosolic factors that mediate nuclear protein import in vertebrates. Previous biochemical studies have shown that NTF2 binds directly to the GDP-bound form of Ran/TC4 and to proteins of the nuclear pore complex that contain phenylalanine-glycine repeats. In the present study we have used molecular genetic approaches to study the Saccharomyces cerevisiae homologue of NTF2. The scNTF2 gene encodes a protein that is 44% identical to the human protein. We found that deletion of the scNTF2 gene is lethal and that repression of NTF2p expression by a regulatable promoter results in gross structural distortions of the nuclear envelope. In a screen for high copy number suppressors of a scNTF2 deletion, the only gene we isolated other than scNTF2 itself was GSP1, the S. cerevisiae homologue of Ran/TC4. Furthermore, we found that high levels of Ran/TC4 can relieve the requirement for NTF2 in a mammalian-permeabilized cell assay for nuclear protein import. These data suggest that certain of the nuclear protein import functions of NTF2 and Ran/TC4 are closely linked and that NTF2 may serve to modulate a transport step involving Ran/TC4.

[Angiotensin-converting enzyme gene polymorphism and the clinical pathological features and progression in lupus nephritis]

The renin-angiotensin system (RAS) is now well established as an important determinant in the progression of renal damage. The level of plasma angiotensin converting enzyme (ACE) is genetically determined and this gene effect is associated with insertion (I)/deletion (D) polymorphism in intron 16 of ACE gene. It has been reported that DD genotype of ACE gene is associated with a poor outcome in patients with IgA nephropathy and trend to develop renal damage in diabetic mellitus. In this study, the correlation between ACE gene I/D polymorphism and the clinical features of lupus nephritis (LN) was determined in 144 LN patients and 150 normal controls by PCR. 72 LN patients were followed up for more than two years. It was found that the DD genotype was significantly higher in LN patients than in normal controls (P < 0.01), while the II genotype was much less in LN (P < 0.01). There was no significant difference in DI genotype frequency between LN patients and normal control (P > 0.05). Patients with hematuria, type IV LN, activation of LN, crescentic formation and severe tubulo-interstitial lesions showed an excess of the DI genotype. However, the DD genotype was not associated with the clinical and pathological characteristics of LN. To assess whether ACE genotype influence the progression of LN, we compared the clinical and pathological findings in patients of different genotype subgroups. There was no significant difference in blood pressure, proteinuria, serum creatinine, active index of disease and crescentic formation at presentation among these groups. However, as patients were divided into two groups according to their rate of decline in renal function. We found that patients with progressive renal function damage had a higher frequency of DI genotype than those with stable renal function (P < 0.01). It is conclude that patients with LN the DI genotype was associated with the severity and the poor prognosis in patients with LN.

Integral membrane proteins of the nuclear envelope are dispersed throughout the endoplasmic reticulum during mitosis

We have analyzed the fate of several integral membrane proteins of the nuclear envelope during mitosis in cultured mammalian cells to determine whether nuclear membrane proteins are present in a vesicle population distinct from bulk ER membranes after mitotic nuclear envelope disassembly or are dispersed throughout the ER. Using immunofluorescence staining and confocal microscopy, we compared the localization of two inner nuclear membrane proteins (laminaassociated polypeptides 1 and 2 [LAP1 and LAP2]) and a nuclear pore membrane protein (gp210) to the distribution of bulk ER membranes, which was determined with lipid dyes (DiOC6 and R6) and polyclonal antibodies. We found that at the resolution of this technique, the three nuclear envelope markers become completely dispersed throughout ER membranes during mitosis. In agreement with these results, we detected LAP1 in most membranes containing ER markers by immunogold electron microscopy of metaphase cells. Together, these findings indicate that nuclear membranes lose their identity as a subcompartment of the ER during mitosis. We found that nuclear lamins begin to reassemble around chromosomes at the end of mitosis at the same time as LAP1 and LAP2 and propose that reassembly of the nuclear envelope at the end of mitosis involves sorting of integral membrane proteins to chromosome surfaces by binding interactions with lamins and chromatin.

A small ubiquitin-related polypeptide involved in targeting RanGAP1 to nuclear pore complex protein RanBP2

We have found that the mammalian Ran GTPase-activating protein RanGAP1 is highly concentrated at the cytoplasmic periphery of the nuclear pore complex (NPC), where it associates with the 358-kDa Ran-GTP-binding protein RanBP2. This interaction requires the ATP-dependent posttranslational conjugation of RanGAP1 with SUMO-1 (for small ubiquitin-related modifier), a novel protein of 101 amino acids that contains low but significant homology to ubiquitin. SUMO-1 appears to represent the prototype for a novel family of ubiquitin-related protein modifiers. Inhibition of nuclear protein import resulting from antibodies directed at NPC-associated RanGAP1 cannot be overcome by soluble cytosolic RanGAP1, indicating that GTP hydrolysis by Ran at RanBP2 is required for nuclear protein import.

Molecular and functional characterization of the p62 complex, an assembly of nuclear pore complex glycoproteins

Macromolecular trafficking across the nuclear envelope involves interactions between cytosolic transport factors and nuclear pore complex proteins. The p62 complex, an assembly of 62, 58, 54, and 45-kD O-linked glycoproteins-localized near the central gated channel of the nuclear pore complex, has been directly implicated in nuclear protein import. The cDNA cloning of rat p62 was reported previously. We have now carried out cDNA cloning of rat p58, p54, and p45. We found that p58 contains regions with FG (Phe, Gly) and PA (Pro, Ala) repeats at both its NH2 and COOH termini separated by a predicted alpha-helical coiled-coil region, while p54 has an NH2-terminal FG and PA repeat region and a COOH-terminal predicted coiled-coil region. p45 and p58 appear to be generated by alternative splicing, with p45 containing the NH2-terminal FG repeat region and the coiled-coil region of p58. Using immunogold electron microscopy, we found that p58/p45 and p54 are localized on both sides of the nuclear pore complex, like p62. Previous studies have shown that immobilized recombinant p62 can bind the cytosolic nuclear import factor NTF2 and thereby deplete transport activity from cytosol. We have now found that immobilized recombinant p58 and p54 also can deplete nuclear transport activity from cytosol, and that p62, p58, and p54 bind directly to the cytosolic nuclear import factors p97 and NTF2. At least in the case of p58, this involves FG repeat regions. Moreover, p58 can bind to a complex containing transport ligand, the nuclear localization sequence receptor (Srp1 alpha) and p97. These data support a model in which the p62 complex binds to a multicomponent particle consisting of transport ligand and cytosolic factors to achieve accumulation of ligand near the central gated channel of the nuclear pore complex.

Structural analysis of the p62 complex, an assembly of O-linked glycoproteins that localizes near the central gated channel of the nuclear pore complex

The p62 complex is an oligomeric assembly of O-linked glycoproteins of the nuclear pore complex that interacts with cytosolic transport factors and is part of the machinery for nuclear protein import. In this study we have purified the p62 complex from rat liver nuclear envelopes and analyzed its structure and composition. The p62 complex consists of four distinct polypeptides (p62, p58, p54, and p45) and has a mass of approximately 234 kDa, calculated from its hydrodynamic properties and supported by chemical cross-linking and scanning transmission electron microscopy. These data suggest that the p62 complex contains one copy of each constituent polypeptide. Analysis of preparations of the p62 complex by electron microscopy using rotary metal shadowing and negative staining revealed donut-shaped particles with a diameter of approximately 15 nm. Immunogold electron microscopy of isolated rat liver nuclear envelopes demonstrated that p62 occurs on both the nucleoplasmic and cytoplasmic sides of the pore complex near the central gated channel involved in active transport of proteins and RNAs. The properties and localization of the p62 complex suggest that it may be involved in binding transport ligands near the center of the nuclear pore complex and in subsequently transferring them to the gated transport channel.

GTP hydrolysis by Ran occurs at the nuclear pore complex in an early step of protein import

Mediated import of proteins into the nucleus involves multiple cytosolic factors, including the small GTPase Ran. Whether Ran functions by interacting with other cytosolic proteins or components of the nuclear pore complex has been unclear. Furthermore, the precise transport step where Ran acts has not been determined. To address these questions, we have analyzed the binding interactions of Ran using permeabilized cells and isolated nuclear envelopes. By light and electron microscope immunolocalization, we have found that Ran accumulates specifically at the cytoplasmic surface of the nuclear pore complex when nuclear import in permeabilized cells is inhibited by nonhydrolyzable analogs of GTP. Ran associates with a peripheral pore complex region that is similar to the area where transport ligands accumulate by depletion of ATP, which arrests an early step of transport. Binding studies with isolated nuclear envelopes in the absence of added cytosol indicate that Ran-GTP directly interacts with a pore complex protein. Using blot overlay techniques, we detected a single prominent polypeptide of isolated nuclear envelopes that binds Ran-GTP. This corresponds to the 358-kD protein RanBP2, a Ran binding pore complex protein recently identified by two-hybrid screening. Thus, RanBP2 is likely to constitute the Ran-GTP-binding site detected at the cytoplasmic periphery of the pore complex. These data support a model in which initial ligand binding to the nuclear pore complex occurs at or near RanBP2, and that hydrolysis of GTP by Ran at this site serves to define commitment to the nuclear import pathway.

Tpr, a large coiled coil protein whose amino terminus is involved in activation of oncogenic kinases, is localized to the cytoplasmic surface of the nuclear pore complex

From a panel of monoclonal antibodies raised against fractions of rat liver nuclear envelopes (NEs), we have identified an antibody, RL30, which reacts with novel nuclear pore complex (NPC) antigens that are not O-glycosylated. By immunofluorescence staining of cultured cells, RL30 reacts exclusively with the NE in a punctate pattern that largely coincides with that of identified NPC proteins. RL30 labels only the cytoplasmic surface of the NPC in immunogold electron microscopy, predominantly in peripheral regions nearby the cytoplasmic ring. In immunoblots of isolated rat liver NEs and cultured rat cells, RL30 recognizes a 265-kD band, as well as a series of 175-265-kD bands in rat liver NEs that are likely to be proteolytic products of p265. Sequencing of peptides from the 175- and 265-kD RL30 antigens of rat liver revealed that they are both closely related to human Tpr, a protein whose amino-terminal 150-250 amino acids appear in oncogenic fusions with the kinase domains of the met, trk, and raf protooncogenes. We found that in vitro translation of human Tpr mRNA yields a major 265-kD band. Considered together, these data indicate that the 265-kD RL30 antigen in the NPC is the rat homologue of Tpr. Interestingly, Tpr contains an exceptionally long predicted coiled coil domain (approximately 1600 amino acids). The localization and predicted structure of Tpr suggest that it is a component of the cytoplasmic fibrils of the NPC implicated in nuclear protein import. Immunofluorescence microscopy shows that during NPC reassembly at the end of mitosis, Tpr becomes concentrated at the NE significantly later than O-linked glycoproteins, including p62. This indicates that reassembly of the NPC after mitosis is a stepwise process, and that the Tpr-containing peripheral structures are assembled later than p62.