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Articles by L Sun
Total Records ( 10 ) for L Sun
  H Wang , Y Wang , L Sun and D. Liu
 

The 3' untranslated region (3' UTR) of eukaryotic mRNA is an important regulation element that affects not only mRNA translation, but also cell growth. We had found that the 3' UTR of CCAAT-enhancer-binding protein β (C/EBPβ) mRNA had tumor suppression activity. Herein, we reported that deletion of two short sequences at both termini of the C/EBPβ 3' UTR reduced the tumor suppression activity of this 3' UTR, as demonstrated by reduced cell growth, colony formation ability, and tumorigenicity in nude mice. It is noteworthy that the only deletion of a single such sequence was enough for the reduction of tumor suppression effect, and the reducing effect of deletion of the sequence near 3' terminus was stronger. Therefore, specific short sequences in the C/EBPβ 3' UTR are crucial for the tumor suppression activity of C/EBPβ.

  L Sun , X Shen , Y Liu , G Zhang , J Wei , H Zhang , E Zhang and F. Ma
 

The mechanism underlining human papillomaviruses (HPVs) causing cancer has been studied extensively, and it was concluded that the high-risk HPVs' E6 targeted and degraded tumor suppressor protein p53, leading to infected cells malignant transformation. In contrast, the low-risk HPVs only cause proliferative but non-invasive lesions of infected epithelia. Therefore, we hypothesized that low-risk HPVs' E6 might interact with p53 in a different pattern. We used a mammalian green fluorescent protein (GFP) expression system to express HPV-18E6 and HPV-6E6 fusion proteins in wild-type (wt) p53 cell lines, 293T and HEK293 cells, to investigate the traffic and location of E6s and p53. The results indicated GFP-18E6 was mainly expressed in nucleus, whereas GFP-6E6 was expressed exclusively in cytoplasm. Endogenous wt p53 was shown to be localized in the nuclei of cells transfected with GFP-18E6. Interestingly, for the first time, we observed that p53 was trapped in the cytoplasm and never translocated into the cell nuclei transfected with GFP-6E6. In conclusion, HPV-6E6 was responsible for the cytoplasmic localization of p53. Therefore, our experiments provide a new insight into the pathogenesis of HPV.

  L Sun , J Li , C Xu , F Yu , H Zhou , L Tang and J. He
 

A device has been invented for protein crystallization by sandwiching the liquid droplet between two surfaces, in which both hydrophilic and hydrophobic surfaces can be used as crystallization substrates. Comparing with the traditional hanging drop method, it can also reduce the evaporation rate of the liquid droplet and provide a stable environment for the crystal growth. In this work, crystal growth experiments for several proteins, especially on the hydrophilic substrate of mica, have shown the positive effect on crystal growth for improving crystallization conditions and the quality of crystals. The features of this new sandwich method and its mechanism have also been discussed.

  L Sun , I. R Konig and N. Homann
 

Aims: Alcohol, tobacco smoke and Barrett's oesophagus as a consequence of gastro-oesophageal reflux are the main risk factors in oesophageal carcinogenesis. All risk factors may induce oxidative stress. Manganese superoxide dismutase (MnSOD) is one important repair enzyme for reactive oxidative stress (ROS)-induced damage. MnSOD polymorphisms in the –9 position of the signal sequence of the protein may lead to critical enzyme deficiency. The aim of the present study was to investigate the role of polymorphisms of MnSOD in patients with oesophageal cancer [n = 170, 61 patients with adenocarcinoma (AC), 109 patients with squamous cell carcinoma (SCC)] compared to heavy drinkers (n = 160) and healthy blood donors (n = 400). Methods: Genotyping was performed by PCR-RFLP analysis using genomic DNA extracted from whole blood. Results: The Ala/Ala genotype was 27.7% in cancer patients (29.5% AC, 26.6% SCC), 23.1% in patients with heavy alcohol abuse and 12.5% in the group of healthy blood donors. These results were not statistically significant after multivariate analysis controlling for age, sex, alcohol, cigarettes and interactions (odds ratio 0.92, 95% confidence interval = 0.63–1.36, for cancer patients versus heavy drinkers; odds ratio 1.02, 95% confidence interval = 0.51–2.03, for cancer patients versus blood donors; analysis by logistic regression). Subjects with an Ala/Ala genotype (81.3 g/day) had a significantly higher alcohol intake than those with Val/Ala (63.9 g/day) or Val/Val (53.8 g/day) genotype (P < 0.00001 by the Kruskal–Wallis test). Conclusions: MnSOD polymorphisms play no role in the genetic predisposition to oesophageal cancer. However, our data suggest a complex gene-to-phenotype interaction between the MnSOD genotype and alcohol misuse.

  J. X Zhang , L Sun and Y. H. Zhang
 

The immunocompetence handicap hypothesis (ICHH) posits that females prefer signals emitted by immunocompetent males over immunocompromised males and that these signals are honest. However, mechanisms of mate choice under an ICHH model may be impacted by levels of genetic variation (inbred animals vs. outbred animals). Here, we conducted 2-choice female preference experiments and chemical analyses of male urine in inbred BALB/c and outbred CD-1 mice, both of which have immunocompromised nude (nu) strains resulting from a Foxn1 gene knockout. We found that inbred BALB/c females but not outbred CD-1 females preferred the urine of healthy males over that of immunocompromised males despite measured differences in the qualities of their urine. There was a clear increase in female-attracting pheromones (such as farnesenes) in the preputial glands and urine metabolites in healthy BALB/c males but no such difference between CD-1 and CD-1 nu males. Therefore, CD-1 male urine failed to provide an honest mate-choice cue for females. Our results suggest that deleterious traits associated with male odor in mice might be jointly affected by the level of inbreeding and immunodeficiency caused by a single-gene knockout.

  Y Lu , Y Zhang , N Wang , Z Pan , X Gao , F Zhang , H Shan , X Luo , Y Bai , L Sun , W Song , C Xu , Z Wang and B. Yang
  Background—

A characteristic of both clinical and experimental atrial fibrillation (AF) is atrial electric remodeling associated with profound reduction of L-type Ca2+ current and shortening of the action potential duration. The possibility that microRNAs (miRNAs) may be involved in this process has not been tested. Accordingly, we assessed the potential role of miRNAs in regulating experimental AF.

Methods and Results—

The miRNA transcriptome was analyzed by microarray and verified by real-time reverse-transcription polymerase chain reaction with left atrial samples from dogs with AF established by right atrial tachypacing for 8 weeks and from human atrial samples from AF patients with rheumatic heart disease. miR-223, miR-328, and miR-664 were found to be upregulated by >2 fold, whereas miR-101, miR-320, and miR-499 were downregulated by at least 50%. In particular, miR-328 level was elevated by 3.9-fold in AF dogs and 3.5-fold in AF patients relative to non-AF subjects. Computational prediction identified CACNA1C and CACNB1, which encode cardiac L-type Ca2+ channel 1c- and β1 subunits, respectively, as potential targets for miR-328. Forced expression of miR-328 through adenovirus infection in canine atrium and transgenic approach in mice recapitulated the phenotypes of AF, exemplified by enhanced AF vulnerability, diminished L-type Ca2+ current, and shortened atrial action potential duration. Normalization of miR-328 level with antagomiR reversed the conditions, and genetic knockdown of endogenous miR-328 dampened AF vulnerability. CACNA1C and CACNB1 as the cognate target genes for miR-328 were confirmed by Western blot and luciferase activity assay showing the reciprocal relationship between the levels of miR-328 and L-type Ca2+ channel protein subunits.

Conclusions—

miR-328 contributes to the adverse atrial electric remodeling in AF through targeting L-type Ca2+ channel genes. The study therefore uncovered a novel molecular mechanism for AF and indicated miR-328 as a potential therapeutic target for AF.

  J Li , H Huang , L Sun , M Yang , C Pan , W Chen , D Wu , Z Lin , C Zeng , Y Yao , P Zhang and E. Song
 

Purpose: We aim to examine miR-21 expression in tongue squamous cell carcinomas (TSCC) and correlate it with patient clinical status, and to investigate its contribution to TSCC cell growth, apoptosis, and tumorigenesis.

Experimental Design: MicroRNA profiling was done in 10 cases of TSCC with microarray. MiR-21 overexpression was quantitated with quantitative reverse transcription-PCR in 103 patients, and correlated to the pathoclinical status of the patients. Immunohistochemistry was used to examine the expression of TPM1 and PTEN, and terminal deoxynucleotidyl transferase–mediated dUTP labeling to evaluate apoptosis. Moreover, miR-21 antisense oligonucleotide (ASO) was transfected in SCC-15 and CAL27 cell lines, and tumor cell growth was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, adherent colony formation, and soft agar assay, whereas apoptosis was determined by Annexin V assay, cytochrome c release, and caspase 3 assay. Tumorigenesis was evaluated by xenografting SCC-15 cells in nude mice.

Results: MiR-21 is overexpressed in TSCC relative to adjacent normal tissues. The level of miR-21 is reversely correlated with TPM1 and PTEN expression and apoptosis of cancer cells. Multivariate analysis showed that miR-21 expression is an independent prognostic factor indicating poor survival. Inhibiting miR-21 with ASO in TSCC cell lines reduces survival and anchorage-independent growth, and induces apoptosis in TSCC cell lines. Simultaneous silencing of TPM1 with siRNA only partially recapitulates the effect of miR-21 ASO. Furthermore, repeated injection of miR-21 ASO suppresses tumor formation in nude mice by reducing cell proliferation and inducing apoptosis.

Conclusions: miR-21 is an independent prognostic indicator for TSCC, and may play a role in TSCC development by inhibiting cancer cell apoptosis partly via TPM1 silencing.

  R Joshi , L Sun and R. Mann
 

Hox proteins frequently select and regulate their specific target genes with the help of cofactors like Extradenticle (Exd) and Homothorax (Hth). For the Drosophila Hox protein Sex combs reduced (Scr), Exd has been shown to position a normally unstructured portion of Scr so that two basic amino acid side chains can insert into the minor groove of an Scr-specific DNA-binding site. Here we provide evidence that another Drosophila Hox protein, Deformed (Dfd), uses a very similar mechanism to achieve specificity in vivo, thus generalizing this mechanism. Furthermore, we show that subtle differences in the way Dfd and Scr recognize their specific binding sites, in conjunction with non-DNA-binding domains, influence whether the target gene is transcriptionally activated or repressed. These results suggest that the interaction between these DNA-binding proteins and the DNA-binding site determines the architecture of the Hox–cofactor–DNA ternary complex, which in turn determines whether the complex recruits coactivators or corepressors.

  J Tang , S Le , L Sun , X Yan , M Zhang , J MacLeod , B LeRoy , N Northrup , A Ellis , T. J Yeatman , Y Liang , M. E Zwick and S. Zhao
 

Human colorectal cancer (CRC) is one of the better-understood systems for studying the genetics of cancer initiation and progression. To develop a cross-species comparison strategy for identifying CRC causative gene or genomic alterations, we performed array comparative genomic hybridization (aCGH) to investigate copy number abnormalities (CNAs), one of the most prominent lesion types reported for human CRCs, in 10 spontaneously occurring canine CRCs. The results revealed for the first time a strong degree of genetic homology between sporadic canine and human CRCs. First, we saw that between 5% and 22% of the canine genome was amplified/deleted in these tumors, and that, reminiscent of human CRCs, the total altered sequences directly correlated to the tumor's progression stage, origin, and likely microsatellite instability status. Second, when mapping the identified CNAs onto syntenic regions of the human genome, we noted that the canine orthologs of genes participating in known human CRC pathways were recurrently disrupted, indicating that these pathways might be altered in the canine CRCs as well. Last, we observed a significant overlapping of CNAs between human and canine tumors, and tumors from the two species were clustered according to the tumor subtypes but not the species. Significantly, compared with the shared CNAs, we found that species-specific (especially human-specific) CNAs localize to evolutionarily unstable regions that harbor more segmental duplications and interspecies genomic rearrangement breakpoints. These findings indicate that CNAs recurrent between human and dog CRCs may have a higher probability of being cancer-causative, compared with CNAs found in one species only.

 
 
 
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