Oncogenic Molecular Mechanism Of Marke's Disease Virus

Marek's Disease (MD) is a contagious, lymphoproliferative disease of domestic chickens caused by highly infectious cell-associated oncogenic alpha-herpesvirus MD virus, in which lymphoproliferactive infiltration in visceral organs, muscles, and peripheral nerves are common features. MDV strains are classified into three catagories based on their pathogenecity. All of them having the ability of pathopoiesis belonging to the MD virus stereotype ?(MDV- ?). It has the important position of MDV in the fields of tumorigenesis and vaccine prevention from malignant neoplasm, because MDV is the first herpesvirus proven to be oncogenic with the experiment. Marek's Disease is also the first and only viral phymatosis that can be successfully prevented by vaccination.This disease was characterized by a high mortality rate and tumorigenesis of internal organs, which has caused heavy economic losses in the industrial world of poultry farming within and outside of China. It is therefore vital to prevent and cure this disease. To date, the development of MD lymphomas has been studied at two different but integrated levels: the host cells and the virus. The most-recent study of the disease is mainly focused on MDV. A number of excellent reviews on this topic cover the historical, oncogenic, immunologic and general aspects of MDV infection. But little is written about tumorigencity of lymphoma and the relationship between lymphoma development and telomere or telomerase activity.Telomeres/ telomerase has been the focus of today's modern biology; associating itself with tumor, gene expression and regulation, aging and cell longevity. Telomerase has been identified in 90% of human tumors and 98% of cultured cell lines, while it is undetectable in most normal somatic cells. So the hypothesis of telomeres/ telomerase in relation to cancer and aging was established. It was presumed that it had significant correlation between the telomerase activities changes and malignant tumor genesis. Telomerase activity was usually high in many tumors caused by viruses, so it is probably one of the important steps during tumorigencity and development. Telomerase activation is the in-negligible step for tumor formation. Telomere DNA shows high conservatism indicating that telomeres have some commonalities in different animals. With MD as neoplastic virus disease model, the study was performed on the role of telomerase activity changes for tumorigencity and development and the role of the telomere and its'related sequences, so as to find and clarify tumorigencity. It is also useful to facilitate human tumor research and cures that will generate great economic and social effects.It is reasonable to presume that the MDV-I genome had an oncogenic gene by itself because it had the ability of rapid oncogenicity. To date, the oncogenic gene in MDV-? are 132-bpr(repeat sequence), pp38 and meq gene. Between them only 132-bpr and meq gene was owned by MDV- I in those specific genes which has been identified by now. But 132-bpr was mainly related with virus attenuated extent or cell passage frequency. So many research focuses was concentrated on meq gene. MDV-encoded protein MEQ protein was constituted by 339 amino acids and its N-terminal -binding protein contains leucine zipper structure (alkalinity region) and C-terminal contains proline repeat region. All of these structures were similar with tumor protein fos/jun family. Thus meq gene was considered to be a kind of endonuclear oncogenic gene. Obviously, it was related with alkaline amino acids region, yet its relation between oncogenic function and its structure was not clear. According to above references, this research was started from meq and L-meq gene that was detected by the PCR method from latent infection chickens by MDV-?. After cloning and sequencing, L-meq-180 was observed between meq gene and L-meq gene. L-meq-180 was inserted into the ORF of meq gene then L-meq gene was formed. To find where L-meq-180 was from, it was inputed the online explore with the Blast of NCBI. It was found that L-meq-180 was from meq gene as a whole sequence. To differentiate the function of these three sequences in the course of tumor formation, three eukaryotic expression recombinant plasmid was constructed, that is pcDNA-meq,pcDNA-L-meq and pcDNA-L-meq-180. Then they were transfected into chick embryo fibroblast (CEF). A relatively Quantitive Real-time PCR method was employed to detect the expression of tumor repressor p53, chTERT and chTR after the transfection experiment, to find the dependability between tumorigenesis of meq gene and telomerase activity. It could further clarify the pathogeny of MD and establish the foundation of molecular mechanism of telomerase function during MD genesis. The results showed that both of meq gene and L-meq-180 sequence could up-regulate the expression level of p53 and chTERT and activate the workings of telomerase. Yet it indicated no obvious impact on the expression level of chTR.While L-meq gene could not up-regulate the expression level of p53 and chTERT and activate the workings of telomerase as meq gene and L-meq-180 sequence. It still can depress the proliferation of MDV in constrast with meq gene.To further search for the protein difference at the protein level, Differential Proteomic was used to explore the differential display proteomics after transfection, Comparison with Genomics. Although the technologies of Proteome was still not perfect, especially in high reproducibility, high flux and resolution, The strategy combining two-dimensional electrophoresis (2-DE) was used to obtain more than 1,500 protein spots successfully. After automatic and naked eye matching with its analysis software, the results showed that there were 19, 16 and 12 different respective protein spots expressed.It would be helpful to complete the theory foundation of prevention and cure in MD to explore the mechanism of tumorigenesis and related tumor research.