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Biomedical subjects

Y Qian

Publications and source records attributed to Y Qian.

At least 145 records · Page 8Linked to original sources
PubMed1999

Functional interactions between herpesvirus oncoprotein MEQ and cell cycle regulator CDK2.

Marek's disease virus, an avian alphaherpesvirus, has been used as an excellent model to study herpesvirus oncogenesis. One of its potential oncogenes, MEQ, has been demonstrated to transform a rodent fibroblast cell line, Rat-2, in vitro by inducing morphological transformation and anchorage- and serum-independent growth and by protecting cells from apoptosis induced by tumor necrosis factor alpha, C2-ceramide, UV irradiation, or serum deprivation. In this report, we show that there is a cell cycle-dependent colocalization of MEQ protein and cyclin-dependent kinase 2 (CDK2) in coiled bodies and the nucleolar periphery during the G1/S boundary and early S phase. To our knowledge, this is the first demonstration that CDK2 is found to localize to coiled bodies. Such an in vivo association and possibly subsequent phosphorylation may result in the cytoplasmic translocation of MEQ protein. Indeed, MEQ is expressed in both the nucleus and the cytoplasm during the G1/S boundary and early S phase. In addition, we were able to show in vitro phosphorylation of MEQ by CDKs. We have mapped the CDK phosphorylation site of MEQ to be serine 42, a residue in the proximity of the bZIP domain. An indirect-immunofluorescence study of the MEQ S42D mutant, in which the CDK phosphorylation site was mutated to a charged residue, reveals more prominent cytoplasmic localization. This lends further support to the notion that the translocation of MEQ is regulated by phosphorylation. Furthermore, phosphorylation of MEQ by CDKs drastically reduces the DNA binding activity of MEQ, which may in part account for the lack of retention of MEQ oncoprotein in the nucleus. Interestingly, the localization of CDK2 in coiled bodies and the nucleolar periphery is observed only in MEQ-transformed Rat-2 cells, implicating MEQ in modifying the subcellular localization of CDK2. Taken together, our data suggest that there is a novel reciprocal modulation between the herpesvirus oncoprotein MEQ and CDK2.

Animals↗
PubMed1999

Saccharomyces cerevisiae RNase H(35) functions in RNA primer removal during lagging-strand DNA synthesis, most efficiently in cooperation with Rad27 nuclease.

Correct removal of RNA primers of Okazaki fragments during lagging-strand DNA synthesis is a critical process for the maintenance of genome integrity. Disturbance of this process has severe mutagenic consequences and could contribute to the development of cancer. The role of the mammalian nucleases RNase HI and FEN-1 in RNA primer removal has been substantiated by several studies. Recently, RNase H(35), the Saccharomyces cerevisiae homologue of mammalian RNase HI, was identified and its possible role in DNA replication was proposed (P. Frank, C. Braunshofer-Reiter, and U. Wintersberger, FEBS Lett. 421:23-26, 1998). This led to the possibility of moving to the genetically powerful yeast system for studying the homologues of RNase HI and FEN-1, i.e., RNase H(35) and Rad27p, respectively. In this study, we have biochemically defined the substrate specificities and the cooperative as well as independent cleavage mechanisms of S. cerevisiae RNase H(35) and Rad27 nuclease by using Okazaki fragment model substrates. We have also determined the additive and compensatory pathological effects of gene deletion and overexpression of these two enzymes. Furthermore, the mutagenic consequences of the nuclease deficiencies have been analyzed. Based on our findings, we suggest that three alternative RNA primer removal pathways of different efficiencies involve RNase H(35) and Rad27 nucleases in yeast.

Base Sequence↗
PubMed1999

[The relation between alpha1-antichymotrypsin gene polymorphism and epsilon4 allele of apolipoprotein E gene in Alzheimer disease in Chinese].

OBJECTIVE: To detect the relation between alpha1-antichymotrpsin(AACT)gene polymorphism and epsilon4 allele of apolipoprotein E (ApoE) gene in Alzheimer disease (AD) in Chinese. METHODS: The gene polymorphisms of ApoE and AACT were genotyped in 125 AD cases and 140 controls with PCR methods and RFLP typing. Then the association between AACT polymorphism and ApoE epsilon4 was analysed. RESULTS: There was no association between AD and any allele or genotype of AACT polymorphism; AACT polymorphism was not associated with AD ApoE epsilon4 or without ApoE epsilon4. In AACT*AT and AACT*TT genotypes, ApoE epsilon4 allele was associated with AD, but no association was observed in AACT*AA genotype. CONCLUSION: AACT may not be associated with AD in Chinese, and this effect can not be influenced by ApoE epsilon4, but AACT gene polymorphism may affect the association between ApoE epsilon4 allele and AD.

Adult↗
PubMed1999

Occupational hazard exposure and at risk drinking.

This study examined associations between workers' reported exposure to occupational hazards and at risk drinking. A sample of 15,907 working adults was drawn from the 1985 National Health Interview Survey (NHIS) (weighted sample represented 85,395,000 workers). This was the only year the NHIS included questions on both occupational hazard exposure and at risk drinking. Occupational hazard exposures included chemical/biological substances, physical hazards, injury risk, and mental stress. At risk drinking was defined as binge drinking and drinking and driving. Prevalence adjusted odds ratios were estimated. Sixty percent of workers reported exposure to one or more occupational hazards with considerable variation among and within occupations. In all, 31% reported binge drinking and 15% drove after drinking too much. In a multivariate analysis that controlled for background characteristics, workers who reported occupational hazard exposures were 1.2 to 1.4 times more likely to engage in binge drinking than workers without exposures. Similar results were found for drinking/driving. All multivariate results were statistically significant. Findings suggest workers who report occupational hazard exposures are at greater risk of both binge drinking and drinking/driving. Occupational and environmental health nurses can lead workplace initiatives to reduce occupational hazard exposure and, simultaneously, invest in health promotion efforts to curb at risk drinking among workers.

Adolescent↗
PubMed1999

[Investigation of Y chromosome and polymorphism of 5 Chinese ethnic groups in Yunnan Province, China].

OBJECTIVE: To investigate the polymorphism of DYS287 in the Han, Dai, Lahu, Wa and Tibetan groups living in Yunnan Province, China. METHODS: YAP element was detected by PCR amplification and agarose gel electrophoresis. RESULTS: With 150bp product in all Han,Dai, Lahu and Wa individuals, YAP element is absent. In 11 Tibetan individuals out of 30, YAP element is present and the PCR product is 455bp. CONCLUSION: As an important and stable genetic marker, DYS287 can provide reliable evidence in evolution study.

China↗
PubMed1999

Blocking effect of puerarin on calcium channel in isolated guinea pig ventricular myocytes.

OBJECTIVE: To identify whether Puerarin (Puer) has blocking effects on L-type calcium channel. METHODS: We used whole-cell recording of patch-clamp techniques to analyse calcium channel current in ventricular myocytes isolated from Langendorff guinea pig hearts by collagenase. RESULTS: In control group, peak calcium channel current was decreased by 10.6% and 29.8% at 5, 10 min of recording time, respectively. For the same period, 0.1 mmol/L Puer reduced calcium current by 23.9% and 72.4%. 0.1 and 1 mmol/L Puer inhibited the amplitude of peak Calcium channel current by 40.6% and 63.2% after perfusing for 10 min. Compared with control group in which "rundown" phenomenon was observed, Puer also demonstrated its blocking effect on L-type channel. While washout of Puer with perfusing solution, calcium channel current went down further instead of recovery. Current-voltage (I-V) curves showed that the levels of calcium channel current were obviously decreased by Puer (both 0.1 mmo/L and 1 mmo/L) form -40 mV to +10 mV. CONCLUSION: Puer has blocking effect on L-type calcium channel in a concentration dependent manner.

Animals↗
PubMed1999

[Study on correlation between in vivo and in vitro tests of biomaterials--correlation between leukocyte chemotaxis test and muscular implant test in rabbits].

The purpose of this study was to investigate the correlation between the results of in vivo and in vitro tests of biomaterials. With muscular implant test and leukocyte chemotaxis test, the levels of tissue toxicity of seven biomaterials were evaluated. The samples with high-level toxicity showed weak leukocyte chemotaxis, which would influence the anti-inflammatory reaction to foreign bodies. By the method of Spearman rank correlation, the coefficient was between 0.89286-0.98198 indicating that the correlation of the two tests is excellent.

Animals↗
PubMed1999

[Cloning and sequencing of cDNA from G protein gene of subgroup B respiratory syncytial virus strain isolated in China].

The nucleotide sequence of the G protein gene of respiratory syncytial virus (RSV) CC169 strain isolated from China that has been identified as subgroup B with monoclonal antibodies, was determined from cDNA that had been amplified by RT-PCR and cloned into pTZ18R plasmid vector. The homology of nucleotide was 94% as compared with G protein cDNA of a RSV prototype strain (CH18537). Deduced amino acid identity of G protein was 89.4%. The amino acid changes were only in the extracellular part of the protein where there were two extensive divergent domains with a highly conserved region in between; whereas the cytoplasmic and transmembrane domains were conserved. This study demonstrates the sequence diversity of the G protein of subgroup B RSV between a Chinese isolate and the prototype strain CH18537.

Amino Acid Sequence↗
PubMed1999

[Expression of VP7 from a group A rotavirus G4 field strain in baculovirus system].

The full length of G4 type VP7 cDNA was amplified by reverse transcription and polymerase chain reaction (RT-PCR) from a group A rotavirus field strain CR117 circulated in Beijing. The amplified cDNA was first cloned into pTZ18. Sequence analysis showed 96.9% homology of the deduced amino acid between VP7 of CR117 and ST3. Then the VP7 cDNA of CR117 was subcloned into the transfer vector pBacPAK8 downstream of the polyhedrin promotor. Insect cells were cotransfected with recombinant plasmid pBacPAK8-CR117 and Bsu36I-digested BacPAK6 viral DNA. Recombinant baculovirus containing CR117 VP7 gene was obtained by plaque screen and hybridization identification. Specific VP7 with three different molecular weight was detected by Western blot using hyperimmune serum against Rotavirus strain ST3 (G4 type) when expressed in insect cells.

Animals↗
PubMed1998

Molecular events after antisense inhibition of hMSH2 in a HeLa cell line.

To establish a cause-effect relationship between the human mismatch repair pathway deficiency and the observed phenotypes, a hMSH2 deficient HeLa cell line (HeLa-MSH2-) was established by transfecting the HeLa cells with an antisense RNA expression plasmid. The expression plasmid was constructed by inserting an 851 bp fragment of hMSH2 cDNA into the polyclonal site of the vector pREP9 in a reversed orientation. The production of the mismatch binding protein, hMSH2, was inhibited in HeLa-MSH2- cells, as demonstrated by Western blotting and band shift assay of its whole cell extract. The growth rate of this cell line was not different from the parental HeLa cells soon after transfection. However, the rate was faster after 10 subcultures. The spontaneous mutation frequency at the hypoxanthine phosphoribosyltransferase (HPRT) locus increased markedly, but no N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) tolerance appeared in this cell line. Our results clearly demonstrated several molecular events happened after the inhibition of a major mismatch recognition protein, hMSH2, in the mismatch repair pathway, mimicking carcinogenesis processes.

Base Pair Mismatch↗
PubMed1998

Regulated phosphorylation and trafficking of antidepressant-sensitive serotonin transporter proteins.

Presynaptic serotonin (5-hydroxytryptamine, 5-HT) transporters (SERTs) mediate antidepressant-sensitive clearance of 5-HT following release. Although we have been aware for decades that SERT-mediated 5-HT clearance can be modulated by exogenous agents including serotonin-selective reuptake inhibitors, amphetamines, and cocaine, we have had little reason to speculate that SERT activity was actively controlled through endogenous pathways. Recent studies indicate that SERTs are likely to be trafficked to specific plasma membrane subdomains to achieve localized clearance of 5-HT, and that the number of SERTs resident in the plasma membrane is controlled through kinase- and phosphatase-linked pathways. In particular, roles for protein kinase C and phosphatase 2A become apparent through studies with enzyme activators and inhibitors in SERT-transfected cells, where SERT proteins are rapidly phosphorylated in parallel with transporter redistribution and loss of functional uptake capacity. Based on our findings, and the studies of others in native tissues and transfected cells, we propose a model whereby SERTs are organized in a macromolecular complex in the plasma membrane that may serve to locate reuptake activity near release sites. Although many elements of this model remain hypothetical, our findings suggest a much more dynamic picture of transporter-mediated 5-HT reuptake than typically described and suggest opportunities both for the development of new SERT regulatory agents and for the identification of regulatory pathways that may be compromised in mental illness.

Animals↗
PubMed1998

A reduction-pyrolysis-catalysis synthesis of diamond

Diamond powder was synthesized through a metallic reduction-pyrolysis-catalysis route with the reaction of carbon tetrachloride and sodium at 700 degreesC, in which the sodium was used as reductant and flux. This temperature is much lower than that of traditional methods. The x-ray powder diffraction patterns showed three strong peaks of diamond. The Raman spectrum showed a sharp peak at 1332 inverse centimeters, which is characteristic of diamond. Although the yield was only 2 percent, this method is a simple means of forming diamond.

Journal Article↗
PubMed1998

Fas-induced proteolytic activation and intracellular redistribution of the stress-signaling kinase MEKK1.

The stress-activated protein kinase (SAPK, alternatively JNK) is activated rapidly by cell stress stimuli such as inflammatory cytokines and oxidative stress, and more slowly by the initiation of the apoptotic cell death response by events such as ligation of the Fas protein. Mitogen-activated protein kinase/Erk kinase kinase-1 (MEKK1) is an activator of SAPK, serving as a SAPK-kinase-kinase through intermediate phosphorylation of the SAPK kinase SEK1. By sequencing proteolytic cleavage products of MEKK1, we found that the proapoptotic protease caspase 3 (CPP32) cleaves MEKK1 after residue D68 both in vivo and in vitro. Cleavage of MEKK1 after D68 is blocked by viral and chemical protease inhibitors. Cleavage of MEKK1 at D68 changes the intracellular distribution of the protein from a Triton-insoluble compartment to a Triton-soluble compartment, reflected in a redistribution from a particulate to a diffuse cytoplasmic staining seen by immunofluorescence. Activation of both SAPK and MEKK1 after Fas ligation is prevented by both viral and chemical caspase 3 inhibitors, which in contrast fail to block activation of SAPK by rapidly acting cell stresses. Stress factor-induced SAPK signaling is not dependent on caspase 3 function. We propose that two mechanisms of stress signaling through MEKK1 exist. One is rapid, independent of proteases, and occurs in the particulate Triton-insoluble compartment. The other is more slowly activated and involves liberation of particulate MEKK1 by proteolytic cleavage and activation by caspase 3.

Animals↗
PubMed1998

Src can regulate carboxy terminal interactions with AFAP-110, which influence self-association, cell localization and actin filament integrity.

The SH2 and SH3 binding partner AFAP-110 is a tyrosine phosphorylated substrate of Src. AFAP-110 has been hypothesized to link Src to actin filaments, which may contribute to the effects of Src upon actin filament integrity. However, it has been unclear what effect activated Src (Src527F) has upon AFAP-110 structure or function and whether AFAP-110 plays a role in actin filament integrity. We report here that the carboxy terminal 127 amino acids of AFAP-110 are comprised of an alpha-helical region that contains a leucine zipper motif. This indicated the potential of AFAP-110 to self-associate. Expression of the carboxy terminus as a fusion protein (GST-cterm) will permit affinity absorption of cellular AFAP-110. The integrity of the alpha-helical leucine zipper motif in GST-cterm is required for affinity absorption, but binding is not due to a classical leucine zipper interaction. Co-expression of Src527F, unlike cSrc, will abrogate affinity absorption of AFAP-110 with GST-cterm. These data indicate that Src527F has affected a change in the carboxy terminal structure that renders AFAP-110 unavailable for affinity absorption. Superose chromatography demonstrate that AFAP-110 will fractionate as a monomer or multimer, indicating AFAP-110 can be detected in a self-associated form in cell lysates. Co-expression of Src527F resulted in AFAP-110 fractionating with a molecular weight that predicts only a multimeric population. Deletional mutagenesis also indicate a biological role for the carboxy terminus in cellular localization and actin filament integrity. Deletion of the entire carboxy terminal alpha-helix (84 amino acids) will not permit AFAP-110 to efficiently colocalize with actin filaments or the cell membrane. Deletion of only the leucine zipper region of the carboxy terminal alpha-helix (44 amino acids) from AFAP-110 (AFAPAdeltazip) demonstrate that both AFAPdeltalzip and actin filaments are repositioned into rosette-like structures, similar to the effects of Src527F, while co-expression of AFAP-110 with cSrc will not affect actin filaments. These data indicate that AFAP-110 can play an important role in modulating actin filament integrity through carboxy terminal interactions that can be affected by Src527F.

Actin Cytoskeleton↗
PubMed1998

Inhibiting Ras prenylation increases the radiosensitivity of human tumor cell lines with activating mutations of ras oncogenes.

The influence of activated ras oncogenes on the sensitivity of human tumor cells to killing by radiation has been an unresolved question in radiobiology. We have examined this question by measuring the radiation sensitivity of human tumor cell lines with oncogenic mutations in their H- or K-ras genes after treatment with prenyltransferase inhibitors that prevent the posttranslational modification of ras required for its activity. Using two measures of clonogenic survival, we have demonstrated radiosensitization in cell lines with oncogenic H-ras mutations or with oncogenic K-ras mutations when ras processing was inhibited by prenyltransferase inhibitor treatment. In contrast, the inhibition of ras processing in cell lines expressing wild-type ras had no effect on radiation-induced cell death. The prenyltransferase inhibitors themselves inhibited clonogenic survival in some cases, but this inhibition did not correlate with ras mutational status. Although treatment with prenyltransferase inhibitors and radiation resulted in a greater reduction of clonogenicity than either treatment alone in cells with wild-type ras, treatment with both agents had a synergistic effect on cell killing in tumor cells with ras mutations. Our results demonstrate that the inhibition of oncogenic ras activity in human tumor cells can reduce the radiation survival of these cells, suggesting that oncogenic ras can contribute to radiation resistance in human tumors. These results further demonstrate the potential of using prenyltransferase inhibitors in combination with radiotherapy in the treatment of human malignancies.

Blotting, Western↗