ARS | Publication request: Identification and in vitro characterization of a Marek’s disease virus encoded ribonucleotide reductase

Submitted to: Avian Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 18, 2012
Publication Date: N/A

Interpretive Summary: Mark’s disease virus (MDV), is the causative agent of Marek’s disease (MD), a cancer-like disease in chickens. The objective of this research was to identify and characterize unknown genes of MDV that may be critical for the pathogenesis of the disease. We have identified a gene named ribonucleotide reductase (RR) that is highly expressed during entire pathogenesis of the disease. This gene encodes an essential enzyme RR for the conversion of ribonucleotides to deoxyribonucleotides in all animal and plant cells. Using monoclonal antibody specific for RR, we found that 45 strains of MDV of three serotypes contain this unique gene. Structural analysis of MDV RR shows large similarity with RR of animal herpesviruses and other species of evolutionary importance. These findings have great importance to the scientists for understanding the mechanism involved in MDV replication in chickens. This knowledge may help in designing future effective vaccines against MD.

Technical Abstract: Marek’s disease virus (MDV) encodes a ribonucleotide reductase (RR), a key regulatory enzyme in the DNA synthesis pathway. The gene coding for the RR of MDV is located in the unique long (UL) region of the genome. The large subunit is encoded by UL39 (RR1) and is predicted to comprise 860 amino acids while the small subunit encoded by UL40 (RR2) is predicted to be 343 amino acids long. Immunoprecipitation analysis of MDV-1 (GA strain)-infected cells with T81, a monoclonal antibody specific for RR of MDV, identified two major proteins of 90,000 and 40,000 Daltons corresponding to RR1 and RR2 respectively. In addition, RR was abundantly expressed in the cytoplasm of cells infected with 51 strains of MDV belonging to MDV serotypes 1, 2 and 3 as demonstrated by immunofloresence staining. Northern blot analysis of RNA extracted from MDV-infected cells showed a major band of around 4.4 Kb in size corresponding to the RR1 and RR2 transcripts. In vivo, RR was abundantly expressed in lymphoid organs and feather follicle epithelium of MDV infected chickens during early cytolytic infection, as determined by immunohistochemistry. The abundant expression of RR in MDV infected chicken may suggest an important role of RR in the conversion of ribonucleotides to deoxyribonucleotides for MDV DNA synthesis.