Marek’s disease virus unique genes pp38 and pp24 are essential for transactivating the bi-directional promoters for the 1.8 kb mRNA transcripts

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(1.8 kb)-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.

Study on the structure of heteropolymer pp38/pp24 and its enhancement on the bi-directional promoter upstream of pp38 gene in Marek’s disease virus

“…Recently, we carried out a transfection with the plasmid pP(1.8 kb)-CAT to qualitatively analyze the enhancement of pp38 to its upstream bi-directional promoter, and the result showed pp38 could significantly enhance the activity of the promoter, which, however, depended on the cooperation of pp24 [12] . In this work, we used EGFP as a reporter, and the transfected results further verified the importance of pp24 to pp38 in the enhancement to the bi-directional promoter.…”

“…Recently, Chloramphenicol acetyltransferase (CAT) gene was used as a reporter to verify that the enhancement of pp38 to the promoter depends on the existence of pp24 [12] . In this work, we used enhanced green fluorescence protein (EGFP) gene as a reporter to confirm that the co-existence of pp38 and pp24 is essential to activity of the bi-directional promoter.…”

Th1 and Th2 Cytokines Activity during Transformation and Lymphoma Formation Stage in Chicken Naturally Infected with Marek's disease virus.

“…Marek's disease virus (MDV) is a highly transmissible cell-associated neuropathic oncogenic alphaherpes virus (Lee et al, 2000;Tulman et al, 2000) affecting poultry health worldwide, characterized by T-cell lymphomas in peripheral nerves and visceral organs (Ding et al, 2007) resulting in considerable economic losses.Three serotypes of MDV have been classified; MDV-1 which is the pathogenic one for chickens, causing marek's disease (MD), is classified as gallid herpes virus II. The second serotype; MDV-2, is gallid herpes virus III and the third and last one is a MDV-3 (as HVT) as meleagrid herpes virus.…”

Construction of Recombinant Marek's Disease Virus (rMDV) Co-Expressing AIV-H9N2-NA and NDV-F Genes under Control of MDV's Own Bi-Directional Promoter

“…They were located on I RL region and separated by a short sequence of only about 305 bp but with several enhancer motifs such as TATA-box, CAAT-box, Oct-1, and Sp1, and as a bi-directional promoter to initiate transcription of two genes in opposite directions [7], [8], [9]. By use of GFP gene and chloramphenicol acetyltransferase ( CAT ) as reporter genes, it was demonstrated that the activity of the bi-directional promoter could be strongly increased by the expression of MDV pp38/pp24 dimers as a trans-acting transcriptional factor [10]. However, it is still unclear whether this bi-directional promoter is able to simultaneously drive two genes expression in both directions.…”