Telomerase activation by Epstein-Barr virus latent membrane protein 1 is associated with c-Myc expression in human nasopharyngeal epithelial cells

Latent membrane protein 1 (LMP1), one of the oncoproteins encoded by Epstein-Barr virus is sufficient for the development of nasopharyngeal carcinoma in vivo and nasopharyngeal epithelial cellular immortalization in vitro. It has also been shown to increase the telomerase activity in primary human nasopharyngeal epithelial cells by an unknown mechanism. We reported here that LMP1 could increase telomerase activity in coordination with LMP1-induced c-Myc expression in LMP1-transfected primary human nasopharyngeal epithelial cells or in a dual-stable LMP1 integrated nasopharyngeal carcinoma cell line with Tet-on regulatory system, named Tet-on-LMP1 HNE2 by PCR-ELISA analysis and reporter gene assay. Blocking of LMP1 expression decreased telomerase activity and c-myc transactivation. Mutagenesis of Myc-responsive E-box elements in the minimal core of hTERT promoter could inhibit the hTERT expression induced by LMP1. Moreover, blocking of c-myc transactivation could further decrease LMP1-mediated hTERT expression. It has been suggested that LMP1 can be used to aid myc control telomerase. In addition, we also found that C-terminus of LMP1, including CTAR1 and CTAR2 domains participated in telomerase activation. Together, these findings suggested that LMP1 activated telomerase via c-myc.

Genetic relationship between olfactory response and fitness in Cotesia glomerata (L.)

The flight response of the parasitic wasp Cotesia glomerata (L.) to semiochemicals from a plant-host complex is subject to genetic variation. The significance of additive genetic variance for the odour-guided behaviour has been demonstrated by bidirectional selection. In order to understand the potential and constraints for phenotypic evolution in olfactory response under the pressure of natural selection, this study was to investigate genetic covariation between the odour-guided behaviour and life-history traits and its genetic correlation with the efficiency of parasitism. A paternal half-sib analysis revealed that there was no significant genetic correlation between this behavioural character and any of three life-history traits examined (the development time of immature stages, the body size of female wasps, the number of female wasps per brood). Comparisons between the selected high and low olfactory-response strains showed the lack of correlated responses in these life-history traits to bidirectional selection on the odour-guided behaviour. On the other hand, genotypic differences in the ability of olfactory response significantly affected the efficiency of parasitism. In comparison with the low olfactory-response strain, female wasps from the high olfactory-response strain were able to parasitize more host larvae in a wider area of habitats. This study provides the first evidence of links between olfactory response and population success in parasitoids from a genetic perspective.

Characterization of an analphoid, neocentromere-positive inv dup 8p marker chromosome using multiplex whole chromosome and sub-telomere FISH analyses

A 30-year-old male patient with mild mental retardation was found to have a small supernumerary marker chromosome (SMC) in 90% of his peripheral blood cells and in 100% of his fibroblast cells. Multiplex whole chromosome and sub-telomere FISH analyses were used to determine that this SMC is an inverted duplicated distal chromosome 8p fragment. Although it was negative for alpha-DNA sequences, this marker had a functional kinetochore (neocentromere) demonstrated by a positive signal with a CENP-C antibody. Apparently intact 8p telomeres at the marker's ends were demonstrated by using a telomere repeat FISH probe. The patient's phenotypically normal mother on G-banding analysis had a small marker chromosome in 8% of her peripheral blood cells in two cultures of the first specimen studied. The marker was not seen in any subsequent maternal peripheral blood or fibroblast specimens. Although it was impossible to further characterize the maternal SMC, it was suggested that the mother had the same marker as the one seen in the proband. Inverted duplicated chromosomal fragments are the most frequent type of analphoid markers. Stable inverted duplicated 8p marker chromosomes were previously reported in three other patients. They all apparently occurred de novo and were found to be positive for kinetochore-associated proteins. Evidence for the possible inheritance of an inverted-duplicated, analphoid SMC was not shown to-date. This study also demonstrates a practical, straightforward approach for analphoid marker characterization in clinical laboratory settings, using whole chromosome multiplex and subtelomere-specific FISH analyses. FISH probes for all sub-telomere chromosomal regions are commercially available and the large majority of analphoid marker chromosomes involve telomere regions.

Selection on olfactory response to semiochemicals from a plant–host complex in a parasitic wasp

Parasitic wasps (parasitoids) use volatiles from the plants infested by phytophagous insects to locate host herbivores, but their behavioural response to such semiochemicals is highly variable. Bi-directional selection on Cotesia glomerata (Hymenoptera: Braconidae) was conducted to investigate the importance of genetic variation in the olfactory response of parasitoids. Female wasps were assessed for flight orientation and landing success in response to the hexane extract from a plant-host complex in a wind tunnel. After the first generation of selection, two strains significantly differentiated in both flight orientation and landing success, and their divergence continued with further selection. The two selected strains genetically differentiated in olfactory perception rather than upwind flight ability. The realized heritability was estimated as 0.248 for flight orientation and 0.216 for landing success. The selection experiment further demonstrated that a prior exposure to the semiochemicals significantly enhanced the subsequent response of female wasps, independent of genetic differences. These results suggest that both genetic component and environmental conditioning have played an important role in the evolution of host selection and utilization by the parasitoid in a tritrophic system.

The Great Wall of China: a physical barrier to gene flow?

One population from each of six plant species along both sides of the Juyong-guan Great Wall, together with one population from each of five species along both sides of a path on a mountain top near Juyong-guan, were selected to study the effect of the Great Wall as a barrier on genetic differentiation between two subpopulations using RAPD markers. Significant genetic differentiation was found between the subpopulations on both sides of the Great Wall. A wind-pollinated woody species, Ulmus pumila, showed less genetic differentiation than four insect-pollinated species: Prunus armeniaca, Ziziphus jujuba, Vitex negundo, and Heteropappus hispidus. Cleistogenes caespitosa, a wind-pollinated perennial herb, displayed more genetic differentiation between subpopulations than the insect-pollinated species because of its propagation strategy. Although AMOVA analysis showed that subpopulations divided by a mountain path had diverged genetically, the variance component between the subpopulations on both sides of the Great Wall was significantly larger than that between the subpopulations at the control site. Therefore, it is reasonable to deduce that the Juyong-guan Great Wall has served as a physical barrier to gene flow between subpopulations separated for more than 600 years.

[Establishment of germinal cell line of Echinococcus granulosus]

AIM

To establish a cell line of Echinococcus granulosus.

METHODS

The proliferating membranes striped from liver cysts in a naturally infected sheep from Urumq were released to monodispersed germinal cells by grinding. The germinal cells were cultivated in the RPMI 1640 medium supplemented with 10%-20% calf serum on collagen-coated 24-well culture plate alternately from passage 1 to passage 14, and then continued. The morphological feature and growth situation were observed by light microscopy. The cultured cells were inoculated into BALB/c mice to identify the infectivity. ELISA was used to determine the immunogenicity of the cells.

RESULTS

The germinal cells have been cultivated continuously up to passage 75. The subcultured cells were circular in shape with smooth surface and had the tendency to form syncytia and tissue-like masses. The cells from this cell line could be stored for at least 15 days in refrigerator at 4 degrees C and 10 months in liquid nitrogen. No cyst materials were detected in the mice inoculated with cells. The antigens from cell line could react with positive sera from mice infected with protoscoleces and sera against secreted antigens of cyst membrane, soluble antigens from cyst membrane, soluble antigens from protoscoleces and SHF.

CONCLUSION

A germinal cell line of Echinococcus granulosus was successfully established.

Progression to AIDS, a clinical AIDS condition and mortality: psychosocial and physiological predictors

BACKGROUND

The primary aim of this study is to examine prospectively the association of stressful life events, social support, depressive symptoms, anger, serum cortisol and lymphocyte subsets with changes in multiple measures of human immunodeficiency virus (HIV) disease progression.

METHODS

Ninety-six HIV-infected gay men without symptoms or anti-retroviral medication use at baseline were studied every 6 months for up to 9 years. Disease progression was defined in three ways using the Centers for Disease Control (CDC) classifications (e.g. AIDS, clinical AIDS condition and mortality). Cox regression models with time-dependent covariates were used, adjusting for control variables (e.g. race, age, baseline, CD4 T cells and viral load, number of anti-retroviral medications).

RESULTS

Higher cumulative average stressful life events and lower cumulative average social support predicted faster progression to both the CDC AIDS classification and a clinical AIDS condition. Higher anger scores and CD8 T cells were associated with faster progression to AIDS, and depressive symptoms were associated with faster development of an AIDS clinical condition. Higher levels of serum cortisol predicted all three measures of disease progression.

CONCLUSIONS

These results suggest that stressful life events, dysphoric mood and limited social support are associated with more rapid clinical progression in HIV infection, with serum cortisol also exerting an independent effect on disease progression.

Studies on the origin and evolution of tetraploid wheats based on the internal transcribed spacer (ITS) sequences of nuclear ribosomal DNA

In this study, the internal transcribed spacer (ITS) sequences of nuclear ribosomal DNA in the tetraploid wheats, Triticum turgidum (AABB) and Triticum timopheevii (AAGG), their possible diploid donors, i.e., Triticum monococcum (AA), Triticum urartu (AA), and five species in Aegilops sect. Sitopsis (SS genome), and a related species Aegilops tauschii were cloned and sequenced. ITS1 and ITS2 regions of 24 clones from the above species were compared. Phylogenetic analysis demonstrated that Aegilops speltoides was distinct from other species in Aegilops sect. Sitopsis and was the most-likely donor of the B and G genomes to tetraploid wheats. Two types of ITS repeats were cloned from Triticum turgidum ssp. dicoccoides, one markedly similar to that from T. monococcum ssp. boeoticum (AA), and the other to that from Ae. speltoides (SS). The former might have resulted from a recent integression event. The results also indicated that T. turgidum and T. timopheevii might have simultaneously originated from a common ancestral tetraploid species or be derived from two hybridization events but within a very short interval time. ITS paralogues in tetraploid wheats have not been uniformly homogenized by concerted evolution, and high heterogeneity has been found among repeats within individuals of tetraploid wheats. In some tetraploid wheats, the observed heterogeneity originated from the same genome (B or G). Three kinds of ITS repeats from the G genome of an individual of T. timopheevii ssp. araraticum were more divergent than that from inter-specific taxa. This study also demonstrated that hybridization and polyploidization might accelerate the evolution rate of ITS repeats in tetraploid wheats.

PCR-based methylation testing for Prader-Willi or Angelman syndromes using archived fixed-cell suspensions

All Prader-Willi syndrome (PWS) and 75% of Angelman syndrome (AS) patients have specific DNA methylation pattern alterations that can be used for diagnostic evaluation. The methylation testing identifies a significantly higher proportion of patients as compared to fluorescence in situ hybridization (FISH)-based microdeletion analysis and is thus a useful diagnostic evaluation for clinically suspect, but FISH-negative, patients. We used two independent PCR-based protocols for methylation testing on fixed cell specimens archived after FISH analyses. Changes in DNA methylation due to the procedure of cell fixation were ruled out by testing control specimens before and after fixation. Then methylation testing was carried out on 20 standard fixed-cell supsensions from people suspected for PWS or AS. These fixed specimens were stored after negative FISH analysis for up to 4 years at 4 degrees C in 3:1 methanol/acetic acid. Methylation patterns associated with AS (one specimen) and with PWS (one specimen) were identified for both protocols. The observed methylation patterns were concordant with the phenotypes of the positive individuals and for the two protocols used. We have, thus, shown that archived fixed-cell suspensions from individuals suspected as PWS or AS that were negative for cytogenetic/FISH microdeletions, can now be re-evaluated with PCR-based methylation testing without the need for additional blood samples from the previously studied individuals.

Genetic identification of a locus, Mot1, that affects renal tumor size in the rat

Prognosis and treatment of solid tumors are directly dependent on the stage of disease. For any type of cancer, tumor characteristics such as size, multiplicity, and metastatic potential are highly heterogeneous among patients. Our understanding of the genetic determinants of tumor burden is rudimentary. Here, rats carrying a germline mutation of the gene Tsc2 were found to develop variable size and number of renal tumors. We hypothesize that "modifier" genes unlinked to Tsc2 affect its expressivity. Using a backcross (BC) analysis between the two strains that showed the greatest difference in tumor size (Fischer344 and Brown Norway), we mapped a quantitative trait locus based on tumor volume to rat chromosome 3q, lying in the interval between D3Mit3 and D3Rat17, with a maximum lod score of 4.4. This locus, Mot1 (modifier of Tsc2 1), accounts for approximately 35% of the genetic variation in tumor size between the two strains. No significant difference in tumor multiplicity was noted between Brown Norway and Fischer344 rats. This suggests that Mot1 modulates the rate of disease progression and not tumor initiation. Candidate genes on rat chromosome 3 included Tsc1, whose product interacts biochemically with the TSC2 protein, but it was excluded on the basis of linkage analysis (LOD=0.01). Comparative genomics suggest that the Mot1 region is represented by human chromosomes 15q and 20pq. Our results provide the first evidence of a modifier gene affecting the Tsc2 pathway in the progression of renal tumorigenesis.

Mapping transient, randomly occurring neuropsychological events using independent component analysis

The feasibility of mapping transient, randomly occurring neuropsychological events using independent component analysis (ICA) was evaluated in an auditory sentence-monitoring fMRI experiment, in which prerecorded short sentences of random content were presented in varying temporal patterns. The efficacy of ICA on fMRI data with such temporal characteristics was assessed by a series of simulation studies, as well as by human activation studies. The effects of contrast-to-noise ratio level, spatially varied hemodynamic response within a brain region, time lags of the responses among brain regions, and different simulated activation locations on the ICA were investigated in the simulations. Component maps obtained from the auditory sentence-monitoring experiments in each subject using ICA showed distinct activation in bilateral auditory and language cortices, as well as in superior sensorimotor cortices, consistent with previous PET studies. The associated time courses in the activated brain regions matched well to the timing of the sentence presentation, as evidenced by the recorded button-press response signals. Methods for ICA component ordering that may rank highly the components of primary interest in such experiments were developed. The simulation results characterized the performance of ICA under various conditions and may provide useful information for experimental design and data interpretation.

A 3.1-kb genomic fragment of Bacillus subtilis encodes the protein inhibiting growth of Xanthomonas oryzae pv. oryzae

AIMS

To clone genes of Bacillus subtilis encoding peptides that inhibit the growth of Xanthomonas orzae pv. oryzae (Xoo).

METHODS AND RESULTS

A 3.1-kb DNA fragment from B. subtilis SO113 encoding peptides that inhibit the growth of Xoo (anti-Xoo, showing an inhibition zone) was isolated from a plasmid library of B. subtilis 6 GM15. Sequence analysis revealed that it contained three complete open reading frames (ORFs): ybcO, ybcS and a novel ORF designated ybcPQ. Deleting the last 96 bp of ybcS from the plasmid eliminated the anti-Xoo activity, suggesting that ybcS is required for producing the anti-Xoo activity. However, no anti-Xoo activity could be detected for the plasmid with ybcS alone. Further analysis showed that ybcO, at least, was also required to obtain the anti-Xoo activity.

CONCLUSIONS

A fragment of B. subtilis has been cloned that expresses an anti-Xoo activity that requires ybcS and ybcO.

SIGNIFICANCE AND IMPACT OF THE STUDY

These genes could be useful for the genetic engineering of resistance to rice bacterial diseases and for the design of new anti-Xoo biocontrol agents.

[Mapping the interaction site of Rpb2 and Rpb3 subunit of fission yeast RNA polymerase II]

To map the interacting site of subunit Rpb2 to subunit Rpb3 of RNA polymerase II in fission yeast Schizosaccharomyces pombe, the yeast two-hybrid system was employed in this paper to screen the interacting clones between Rpb2 and Rpb3.4 fragments of Rpb2 cDNA were cloned into the Ga14 BD vector pAS2. The 4 clones were named as pAS2 Rpb2-1, 2-2, 2-3 and 2-4, respectively. The complete cDNA of Rpb3 was cloned into the Gal 4 AD vector pGADGH. The clone was named as pGADGH Rpb3. The two-hybrid plasmids pGADGH Rpb3 and pAS2Rpb2-1, 2-2, 2-3 or 2-4 respectively were cotransformed into host cell yeast Y190. The interaction positive cotransformants were identified by beta-gal activity assay. The beta-gal positive cotransformants were selected from pGADGH Rpb3 and pAS2Rpb2-4 two-hybrid system. DNA sequencing and alignment results showed that the interacting site of Rpb2 to Rpb3 located within the fragment from base 2701 to 2966 of Rpb2 cDNA, or within the C-termini polypeptide from amino acid 902 to 989 of Rpb2 protein.

A novel water-soluble fluorescent probe for the determination of methylamine

A novel water-soluble fluorescent probe, monosodium 7-(4,6-dichloro-1,3,5-triazinylamino)-1,3-naphthalenedisulfonic acid (DTND), was synthesized by reacting cyanuric chloride with 7-amino-1,3-naphthalenedisulfonic acid monopotassium salt at 0-5 degrees C. This new reagent was used for the determination of methylamine. The linear range is 3x10(-6)-2x10(-4) mol L(-1) with a detection limit (S/N=3) of 7.2x10(-8) mol L(-1), and the relative S.D. is 1.3% for ten replicate determinations of 1x10(-5) mol L(-1) CH3NH2. Common species in the aqueous environment have no or only slight influence on the determination. The method can be used to determine methylamine in real water samples.

Evaluation of diagnostic criteria for atopic dermatitis: validity of the criteria of Williams et al. in a hospital-based setting

BACKGROUND

Surveys of the prevalence of atopic dermatitis (AD) have been carried out world-wide, but the results vary widely. The differences probably result from the use of different diagnostic criteria. Williams et al. proposed minimum, simplified, diagnostic criteria that require no invasive test and are easy to use. Pilot studies in European countries showed their suitability for implementation both in hospitals and in the community, and their high sensitivity and specificity.

OBJECTIVES

To evaluate the potential practical value of the criteria of Williams et al. in the Chinese population.

METHODS

The criteria of Hanifin and Rajka (gold standard), Williams et al. and Kang and Tian were applied and compared in 111 patients with AD and 121 control subjects with other skin diseases in three out-patient centres in China.

RESULTS

The criteria of Williams et al. showed a similar diagnostic efficiency to that of the gold standard, with the sensitivity, specificity and kappa value reaching 95.50%, 97.52% and 0.93, respectively. No significant difference was found between the criteria of Williams et al. and those of Kang and Tian (chi2 = 0.69, P > 0.05). 'Onset under the age of 2 years', a criterion of Williams et al. could be used in subjects of any age.

CONCLUSIONS

The diagnostic efficiency of the criteria of Williams et al. was basically similar to those of Hanifin and Rajka and of Kang and Tian in our out-patient settings. However, those of Williams et al. were easier to apply and required no invasive tests.

A positive regulatory role for Cbl family proteins in tumor necrosis factor-related activation-induced cytokine (trance) and CD40L-mediated Akt activation

Tumor necrosis factor (TNF)-related activation-induced cytokine (TRANCE) is a TNF family member essential for osteoclast differentiation, and it induces the activation and survival of osteoclasts and mature dendritic cells. We recently demonstrated that TRANCE activates Akt via a mechanism involving TRANCE receptor (TRANCE-R)/RANK, TRAF6, and c-Src. Here, we show that TRANCE-R and CD40 recruit TRAF6, Cbl family-scaffolding proteins, and the phospholipid kinase phosphatidylinositol 3-kinase in a ligand-dependent manner. The recruitment of Cbl-b and c-Cbl to TRANCE-R is dependent upon the activity of Src-family kinases. TRANCE and CD40L-mediated Akt activation is defective in Cbl-b -/- dendritic cells, and CD40L-mediated Akt activation is defective in c-Cbl -/- B cells. These findings implicate Cbl family proteins as not only negative regulators of signaling but as positive modulators of TNF receptor superfamily signaling as well.

Gab2 is phosphorylated on tyrosine upon interleukin-2/interleukin-15 stimulation in mycosis-fungoides-derived tumor T cells and associates inducibly with SHP-2 and Stat5a

Cutaneous T cell lymphomas (CTCLs) often show abnormal interleukin-2 (IL-2) receptor signaling. In this study, we investigated the role of Gab2, a recently identified adaptor molecule involved in IL-2 receptor signaling in CTCLs. We show that Gab2 was transiently phosphorylated by tyrosine in human mycosis fungoides (MF) tumor T cells upon IL-2 stimulation and that SHP2 as well as Stat5a associated inducibly with Gab2. IL-15, but not IL-4, also induced tyrosine phosphorylation of Gab2, suggesting that the IL-2 receptor beta-chain is important for IL-2-induced Gab2 phosphorylation. Preincubation of cells with the Src family kinase inhibitor, PP1, surprisingly increased the IL-2- and IL-15-induced tyrosine phosphorylation of Gab2, indicating that an Src family kinase member negatively regulates IL-2 receptor signaling in MF T cells. Thus, although Gab2 seems to function normally in MF T cells compared to normal T cells, Gab2 itself might be abnormally regulated by an Src family kinase.

Different classifications of UPOs in the parametrically different chaotic ISI series of a neural pacemaker

Various interspike intervals (ISIs) in a series of spontaneous discharges of experimental neural pacemakers were identified as chaotic and as lying between stable period 2 and stable period 3. The method of So et al. for detection of unstable periodic orbits (UPOs) was applied to analyze two chaotic ISI series generated under the action of [Ca2+]o in different concentrations. In the chaotic ISI series near the stable period 2, an unstable period 2 orbit was detected. In the chaotic ISI series near the stable period 3, both an unstable period 2 orbit and an unstable period 3 orbit were detected. The location of the unstable period 2 orbit was close to that of the stable period 2 in the return map, while the location of the unstable period 3 orbit was close to that of the stable period 3. The results not only revealed the structures of various chaotic ISI series, but also indicated that the classification of UPOs could reflect the experimental control parameters at which the chaotic ISI series were generated. The previously discovered period adding bifurcation in the ISI series generated by experimental neural pacemakers [12] was further described in terms of the evolution of the period orbits.

Essential role for Gab2 in the allergic response

Dos/Gab family scaffolding adapters (Dos, Gab1, Gab2) bind several signal relay molecules, including the protein-tyrosine phosphatase Shp-2 and phosphatidylinositol-3-OH kinase (PI(3)K); they are also implicated in growth factor, cytokine and antigen receptor signal transduction. Mice lacking Gab1 die during embryogenesis and show defective responses to several stimuli. Here we report that Gab2-/- mice are viable and generally healthy; however, the response (for example, degranulation and cytokine gene expression) of Gab2-/- mast cells to stimulation of the high affinity immunoglobulin-epsilon (IgE) receptor Fc(epsilon)RI is defective. Accordingly, allergic reactions such as passive cutaneous and systemic anaphylaxis are markedly impaired in Gab2-/- mice. Biochemical analyses reveal that signalling pathways dependent on PI(3)K, a critical component of Fc(epsilon)RI signalling, are defective in Gab2-/- mast cells. Our data identify Gab2 as the principal activator of PI(3)K in response to Fc(epsilon)RI activation, thereby providing genetic evidence that Dos/Gab family scaffolds regulate the PI(3)K pathway in vivo. Gab2 and/or its associated signalling molecules may be new targets for developing drugs to treat allergy.

[A gene study on multidrug resistance of retinoblastoma]

OBJECTIVE

To investigate the expression of multidrug resistance gene (MDR1) and multidrug associated protein (MRP) gene in the retinoblastoma (Rb) cell line HXO-RB(44), and study the mechanism of multidrug resistance (MDR) phenotype occurring in retinoblastoma.

METHODS

Reverse transcriptase polymerase chain reaction (RT-PCR) was employed to detect the transcription of MDR1 and MRP gene in the HXO-RB(44) cell line, and immunohistochemical technique was used to detect their protein products P-glycoprotein and multidrug resistance associated protein (P190).

RESULT

Both MDR1 and MRP genes were expressed in HXO-RB(44) cell line, as well as P-glycoprotein and P190 were over-expressed (96% - 97%) in this cell line.

CONCLUSION

Over-expression of MDR1 and MRP genes is significantly involved in the mechanism of MDR phenotype in retinoblastoma.

Position and sequence requirements for poly(A) length regulation by the poly(A) limiting element

The poly(A)-limiting element (PLE) is a cis-acting sequence that acts to limit poly(A) tail length on pre-mRNA to <20 nt. Functional PLEs are present in a number of genes, underscoring the generality of this control mechanism. The current study sought to define further the position requirements for poly(A) length regulation and the core sequence that comprises a PLE. Increasing the spacing between the PLE and the upstream 3' splice site or between the PLE and the downstream AAUAAA had no effect on poly(A) length control. However, moving the PLE from the terminal exon to either an upstream exon or intron eliminated poly(A) length control. Poly(A) length control was further evaluated using a battery of constructs in which the PLE was maintained in the terminal exon, but where upstream introns were either deleted, modified, or replaced with a polypyrimidine tract. Poly(A) length control was retained in all cases, indicating that the key feature is the presence of the PLE in the terminal exon. A battery of mutations demonstrated the importance of the 5' pyrimidine-rich portion of the element. Finally, UV crosslinking experiments identified an approximately 62-kDa protein in Hela nuclear extract that binds to a wild-type 23-nt PLE RNA oligonucleotides but not to a mutated nonfunctional form of the element.

[Increase of EGFR expression by Epstein-Barr virus LMP1 in nasopharyngeal carcinoma cells]

OBJECTIVE

To investigate the effect of LMP1 on the expression of epidermal growth factor receptor (EGFR) in HNE2-LMP1 cells.

METHODS

Stable transfectant HNE2 cell line expressing LMP1 (HNE2-LMP1) or its mutants (HNE2 del 187-351, HNE2 1-231, HNE2 1-187) were used as cell models. The expression of EGFR was detected by Western blot method. The characteristics of EGFR expression were analyzed when HNE2-LMP1 LMP1 cells were transiently transfected with TRAF1, 2, 3 or TRAF1, 2, 3 dominant negative mutants (DN-TRAF1, 2, 3). The growth characteristics of HNE2-LMP1 and vector controls were analyzed on serum-free media supplemented with EGF.

RESULTS

Stable expression of LMP1 in HNE2 cells increased the expression of EGFR. LMP1 CTAR1 domain, being identical to the TRAF interaction domain, was essential to the induction of EGFR. The CTAR2 domain did not induce expression of EGFR. Overexpression of either TRAF1, 3 or an dominant negative mutant of TRAF1, 3 inhibited the expression of EGFR, while TRAF2 or negative mutants of TRAF2 did slightly so. In HNE2-LMP1 cells, LMP1 expression increased the proliferative response to EGF while the vector control cells exhibited very low level of viability and did not proliferate.

CONCLUSION

The induction of EGFR by LMP1 CTAR1 may be an important component of EBV infection via an TRAF1, 2, 3 mechanism in the epithelial cells and may contribute to the development of epithelial malignancies such as nasopharyngeal carcinoma.