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Title: MAREK'S DISEASE VIRUS LATENT PROTEIN MEQ: DELINEATION OF AN EPITOPE IN THE BR1 DOMAIN INVOLVED IN NUCLEAR LOCALIZATION

Author
item Lee, Lucy
item LIU, J-L - UC DAVIS CANCER CENTER
item CUI, X-P - USDA ARS MWA ADOL
item KUNG, H-J - UC DAVIS CANCER CENTER

Submitted to: Virus Genes
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/10/2003
Publication Date: 12/1/2003
Citation: Lee, L.F., Liu, J., Cui, X., Kung, H. 2003. Marek's disease virus latent protein meq: delineation of an epitope in the br1 domain involved in nuclear localization. Virus Genes. 27(3):211-218.

Interpretive Summary: Marek's disease (MD), a virus-induced cancer-like disease of chickens, is a major disease problem in commercial poultry. Vaccination has dramatically reduced the incidence of the disease, but very little is known about the basic mechanisms involved in the induction of disease. The objective of this research was to study an important gene of MD virus termed MEQ gene which is the hallmark for tumor induction. A critical reagent (monoclonal antibody) was developed in order to identify this genes product (protein molecules)in tumors. This report is the first in identifying and mapping the antigenic site for binding of monoclonal antibody to certain region of the MEQ gene. The information obtained from this research is of great interest to scientists and academia as it will aid in generating new knowledge on the mechanism of tumor induction.

Technical Abstract: Marek's disease virus latent protein MEQ (MDV Eco Q) is abundantly expressed and consistently detected in MDV-induced tumors and cell lines. A monoclonal antibody (Mab 23.46) was produced using recombinant fowlpox virus expressing MEQ as an antigen. The isotype of Mab23.46 is IgG1 and specific to MEQ protein. Using this monoclonal antibody, we detected abundant expression of MEQ in rFPV, recombinant baculovirus, and lymphoid tumors induced by Md5 strain of MDV and a small percentage of MD tumor cell line MSB cells. MEQ is a latent protein and it is only expressed in tumor cell and not in productive infected cells. In order to delineate the epitope of MEQ reactive with monoclonal antibody, four deletion mutants were constructed in the basic region of MEQ, namely basic region 1 (BR1) and basic region 2 (BR2). The BR2 has been shown to be the major nuclear localization signal (NLS) and sole nucleolar localization signal (NoLS) whereas BR1 provides a supplementary signal for nuclear entry. Mutants with deletions in the N-terminal region including BR1, (BR1), and (BR1&2) completely abolished the specific binding of monoclonal antibody as demonstrated by Western blot analysis and immunofluoresence test. Deletion of BR2 (BR2) and the C-terminal (bZIP) domain, still allow antibody binding. These data provide direct evidence that MEQ reactive epitope is mapped to the BR1 domain of the molecule. Since both BR1 and BR2 domains contain sequences important for nuclear entry, it is now possible to further study and elucidate the mechanisim of MEQ's involvement in nuclear transportation.