Ming-Ming Pan

Beijing Centers for Disease Control and Prevention, Peping, Beijing, China

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Publications (5)10.7 Total impact

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    ABSTRACT: The human papillomavirus (HPV) E2 protein is a multifunctional DNA-binding protein. The transcriptional activity of HPV E2 is mediated by binding to its specific binding sites in the upstream regulatory region of the HPV genomes. Previously we reported a HPV-2 variant from a verrucae vulgaris patient with huge extensive clustered cutaneous, which have five point mutations in its E2 ORF, L118S, S235P, Y287H, S293R and A338V. Under the control of HPV-2 LCR, co-expression of the mutated HPV E2 induced an increased activity on the viral early promoter. In the present study, a series of mammalian expression plasmids encoding E2 proteins with one to five amino acid (aa) substitutions for these mutations were constructed and transfected into HeLa, C33A and SiHa cells. CAT expression assays indicated that the enhanced promoter activity was due to the co-expressions of the E2 constructs containing A338V mutation within the DNA-binding domain. Western blots analysis demonstrated that the transiently transfected E2 expressing plasmids, regardless of prototype or the A338V mutant, were continuously expressed in the cells. To study the effect of E2 mutations on its DNA-binding activity, a serial of recombinant E2 proteins with various lengths were expressed and purified. Electrophoresis mobility shift assays (EMSA) showed that the binding affinity of E2 protein with A338V mutation to both an artificial probe with two E2 binding sites or HPV-2 and HPV-16 promoter-proximal LCR sequences were significantly stronger than that of the HPV-2 prototype E2. Furthermore, co-expression of the construct containing A338V mutant exhibited increased activities on heterologous HPV-16 early promoter P97 than that of prototype E2. These results suggest that the mutation from Ala to Val at aa 338 is critical for E2 DNA-binding and its transcriptional regulation.
    BMC Molecular Biology 02/2012; 13:5. · 2.80 Impact Factor
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    ABSTRACT: Prion protein (PrP) is able to bind with tubulin and to interfere with the formation of microtubule. To investigate the influence of accumulation of cytosolic PrP in cytoplasm on microtubule, plasmid pcDNA3.1-PrP23-230 expressing human PrP23-230 was introduced into HeLa cells. Immunoprecipitation assays identified the molecular interaction between cytosolic PrP and cellular tubulin. Confocal microscopy showed the co-localization of the expressed cytosolic PrP with tubulin in cytoplasm. Immunofluorescent assays of tubulin illustrated remarkable disruption of microtubular structures in the cells accumulated with cytosolic PrP. Meanwhile, the expressed cytosolic PrP significantly reduced cell viability and induced cell apoptosis. The amounts of microtubule protein in the cells expressing cytosolic PrP were decreased. Moreover, the levels of endogenous tubulin in the brain tissues of scrapie-infected hamsters were significantly lower than that of normal one. It highlights a close linkage between disruption of microtubule framework and cell death caused by abnormal presence of cellular PrP in cytoplasm. The association of apoptosis with microtubule-disrupting activity caused by cytosolic PrP may further provide insight into the unresolved biological function of PrP in the neurons.
    Journal of Molecular Neuroscience 03/2011; 43(3):316-25. · 2.89 Impact Factor
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    ABSTRACT: Prion protein (PrP) is a ubiquitous conserved glycoprotein predominantly expressed in neurons of the central nervous system (CNS). To elucidate on its cellular function, we performed a yeast two-hybrid screen within an adult human brain cDNA library for potential PrP-binding molecules. A novel protein, HS-1 associated protein X-1 (HAX-1), was identified to be able to bind with PrP strongly. The interaction between the two proteins has been further verified by glutathione-S-transferase (GST) pull-down and immunoprecipitation assays. The minimal binding regions were mapped to the segments of residues aa 91–163 for PrPC and residues aa 38–129 for HAX-1. Immunofluorescent assays of co-expressions of human PrP and HAX-1 in 293T and SHSY-5Y cells revealed marked co-localizations of those two proteins in cytoplasm. Moreover, the co-expression of HAX-1 and wild-type PrP (PG5) was found to enhance the cellular resistance to the challenge of H2O2. Contrarily, co-transfection of HAX-1 did not reverse but aggravated the cytotoxicities of the genetic CJD (gCJD) associated PrP mutants with nine- (PG9) and fourteen-octarepeats (PG14). Our data provide for the first time a new PrP-interacting partner that may play role in cell oxidative stress and anti-apoptosis physiologically and cell damage pathologically.
    Journal of Molecular Neuroscience 02/2011; · 2.89 Impact Factor
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    ABSTRACT: HPV-2 is a very common type of HPV which causes common warts. The E2 protein of virus can repress the activity of the viral early promoter through binding to the specific binding sites in viral LCR. Previously we reported that the repression of a mutated E2 protein of HPV-2 isolated from a patient with huge common wart on the viral early promoter was obviously decreased, and A338V mutation located at the C terminal DNA binding region of E2 protein. In this study, we expressed and purified the recombinant mutated and prototype E2 fusion proteins, both in the contexts of the C terminal and the full length, by prokaryotic expression system. The electrophoretic mobility shift assay showed E2 protein could bind to double-stranded DNA oligos labeled with biotin that covered two E2 binding sites. The DNA binding abilities of both C terminal and full-length mutated E2 proteins were stronger than the prototype analogs. This result indicates that the enhancement of the mutated E2 DNA binding ability may be the molecular mechanism for its impact on the activity of viral promoter, which correlates with the phenotype of extensive common wart.
    Bing du xue bao = Chinese journal of virology / [bian ji, Bing du xue bao bian ji wei yuan hui] 05/2010; 26(3):223-7.
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    ABSTRACT: Nerve growth factor (NGF), a member of the neurotrophin family, is essential for the development and maintenance of sensory neurons and for the formation of central pain circuitry. The current study was designed to evaluate the expression of NGF in the brain of rats with spared nerve injury (SNI), using immunohistochemical technique. The results showed that the level of NGF in the Red nucleus (RN) of SNI rats was apparently higher than that of sham-operated rats. To further study the effect of NGF in the development of neuropathic pain, different doses of anti-NGF antibody (20, 2.0 and 0.2 microg/ml) were microinjected into the RN contralateral to the nerve injury side of SNI rats. The data suggested that the higher doses of anti-NGF antibody (20 and 2.0 microg/ml) significantly attenuated the mechanical allodynia of neuropathic rats, while the 0.2 microg/ml antibody showed no analgesic effect. These results suggest that the NGF of RN is involved in the development of neuropathic allodynia in SNI rats.
    Neurochemical Research 04/2009; 34(9):1612-8. · 2.13 Impact Factor