IDENTIFICATION AND CHARACTERIZATION OF A MAREKS-DISEASE VIRUS GENE ENCODING DNA-POLYMERASE

DNA sequence analysis revealed a gene encoding the Marek's disease vir us (MDV) DNA polymerase (pol) within the BamHI-E fragment of the long unique region of the virus genome. Identification is based on an exten sive amino acid homology between the MDV open reading frame and the DN A pol (UL30) of the herpes simplex virus. We describe here a 3540-base -pair fragment of the MDV DNA encoding 1180 amino acids with a Mr of 1 33,920 daltons as the viral DNA pol gene, with the analysis of transcr iption and translation. In Northern blot hybridization, a transcript o f 4.0 kb was detected in GA-MDV-infected duck embryo fibroblast (DEF) cells. An antiserum was generated in rabbit using TryE-pol fusion prot ein expressed in E. coli. This antiserum specifically immunoprecipitat ed a protein of 135 kD from lysates of MDV-GA-infected DEF cells. MDV DNA pol showed extensive homology to five distantly related herpesviru ses: equine herpesvirus (EHV), varicella-zoster virus (VZV), herpes si mplex virus type 1 (HSV-1), Epstein-Barr virus (EBV), and human cytome galovirus (HCMV). Comparison of amino acid sequences among the herpesv iruses highlights nine highly conserved regions. Three of the conserve d regions are in the N-terminus in the 3'-5' exonuclease domains and t he remaining six are in the C-terminus in the catalytic domains. The p redicted structural characters are in good agreement with the publishe d data on a number of human herpesvirus DNA pol. The identification of MDV DNA pol gene may lead to a better understanding of MDV replicatio n.