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Title: THE ROLE OF PP38 IN REGULATION OF MAREK'S DISEASE VIRUS BI-DIRECTIONAL PROMOTER BETWEEN PP38 AND 1.8-KB MRNA

Author
item DING, JIABO - SHANDONG AGRIC UNIV
item CUI, ZHIZHONG - SHANDONG AGRIC UNIV
item Lee, Lucy
item CUI, XIAOPING - MICHIGAN STATE UNIV
item REDDY, SANJAY - TEXAS A&M

Submitted to: Virus Genes
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/1/2006
Publication Date: 4/1/2006
Citation: Ding, J., Cui, Z., Lee, L.F., Cui, X., Reddy, S. 2006. The role of pp38 in regulation of Marek's disease virus bi-directional promoter between pp38 and 1.8-kb mRNA. Virus Genes. 32(2):193-201.

Interpretive Summary: Marek's disease (MD), a virus-induced cancer-like disease in chickens, is considered 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 molecularly characterize Marek’s disease virus (MDV) so that successful programs to control the disease can be developed. We have discovered a unique MDV gene (genetic building block) termed RLORF14a encodes pp38 which was shown to be involved in early cytolytic infection in chickens. Deletion of pp38 in pathogenic rMd5 virus resulted in less tumors in inoculated chickens. In this paper, we found pp38 is critical in up-regulating MDV bi-directional promoter between pp38 and 1.8 kb mRNA. This means pp38 can influence itself or l.8 kb mRNA gene family in producing protein product necessary for pathogenesis of MDV. This important information will help scientists in academia better understand the function of this viral gene. Undoubtedly, it will help industry with a possible vaccine for better control of the disease.

Technical Abstract: Marek’s disease virus contains a bi-directional promoters located between pp38 gene and 1.8-kb mRNA in the long inverted repeat region of the viral genome. The involvement of pp38 gene in up-regulating the activity of these promoters was analyzed by transient expression of chloramphenicol acetyltransferase (CAT) reporter gene. Two CAT reporter plasmids, pP(pp38)-CAT and pP(1.8-kb)-CAT, were constructed to express CAT under the control of the bi-directional promoter in both orientations. These plasmids were transfected into chicken embryo fibroblast (CEF), infected with rMd5 and pp38 deleted rMd5 (rMd5/'pp38), respectively. No CAT activity was detected in uninfected CEF as expected. CAT activities in rMd5/'pp38 virus infected CEF (rMd5/'pp38-CEF) were 3.5-fold lower using pP(pp38)-CAT and 12-fold lower using pP(1.8-kb )-CAT than those of the parental rMd5 infected CEF (rMd5-CEF). The significantly lower promoter activity in the pp38 deletion virus suggests that pp38 can regulate the activity of the bi-directional promoters, especially in the direction of 1.8-kb mRNA family. Co-transfection of pp38-expressing plasmid (pcDNA-pp38) into rMd5/'pp38-CEF significantly increased the activity of the bi-directional promoters using either pP(pp38)-CAT or pP(1.8-kb)-CAT. DNA mobility shift assay showed a binding of the 73-bp sequence of the bi-directional promoter with rMd5-CEF but not with rMd5/'pp38-CEF or uninfected CEF lysates. However, rMd5/'pp38-CEF lysates could bind the same 73-bp promoter sequence when co-transfected with pp38-expressing plasmid (pcDNA-pp38). All these data taken together suggest pp38 plays an important role in regulating the transcriptional activity of the bi-directional promoter.