Submitted to: Virus Genes
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/5/2007
Publication Date: 12/1/2007
Citation: Ding, J., Zhizhong, C., Lee, L.F. 2007. Marek's disease virus unique genes pp38 and pp24 are essential for transactivating the bi-directional promoters for the 1.8 kb mRNA transcripts. Virus Genes. 35:643-650. 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 blocks) 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 and pp24 together are critical in up-regulating MDV bi-directional promoter for 1.8 kb mRNA. This means both genes can influence l.8 kb mRNA gene family in producing protein product necessary for pathogenesis of MDV. This important information will help scientists in academia to understand the function of these viral genes better. Undoubtedly, it will help industry with a possible vaccine for better control of the disease.
Technical Abstract: The pp38 and pp24 genes of Marek’s diseases virus (MDV) share the same promoter, which controls the transcription of pp38 or pp24 and a 1.8-kb mRNA bi-directionally. To understand the trans-activating activity of pp38 and pp24 on the bi-directional promoter, both genes were cloned into pcDNA-3 or pBudCE4.1 vectors either singly or in combination. These plasmids were expressed in transfected chicken embryonic fibroblast (CEF) cells. Chloramphenicol acetyltransferase (CAT) activity expressed under the control of the promoter in CEF co-transfected with pP (1.8kb)-CAT and pBud-pp38-pp24 was significantly higher than that following transfection with only pBud-pp38 or pBud-pp24. This indicates the combination of pp24 and pp38 together are essential for the activation of the promoter. In DNA mobility shift assays, the promoter binds to pp38 and pp24 together, but not to pp38 or pp24 alone. By competitive inhibition tests with a set of DNA fragments from the promoter region, the sequence 5’-CTGCTCATTT-3’ was identified as the core sequence for binding by pp38-pp24 in up-regulation of the bi-directional promoter activity.