Identification and structure of the Marek's disease virus serotype 2 glycoprotein M gene: Comparison with glycoprotein M genes of Herpesviridae family

We determined the nucleotide sequence of a portion of BamHI-C fragment of M arek's disease virus serotype 2 (MDV2) strain HPRS24 which was suspected to contain the homologue of the herpes simplex virus type 1 (HSV-1) gene UL10 , encoding glycoprotein M (gM). An open reading frame whose translation pro duct exhibited significant similarities to HSV-I gM protein and respective proteins of other herpesviruses of 37.5% and 45.5% to 31.8%, respectively, was identified. A number of distinct transcriptional consensus sequences we re found upstream of the first putative start codon of MDV2 UL10 protein. I n transcriptional analysis, the gene was transcribed into an 1.5 kb RNA. Th e primary translation product comprises 424 amino acids with a predicted mo lecular weight of 46.9 kDa. The predicted MDV2 UL10 protein contains eight hydrophobic domains with sufficient length and hydrophobicity to span the l ipid bilayer conserved in the genomes of all herpesviruses which have been sequenced so far. In the region located between the first and second hydrop hobic domains, two potential N-linked glycosylation sites were presented. I nterestingly, highly charged residues were abundantly possessed in the carb oxy-terminal part of the MDV2 UL10 protein. By comparison of the amino acid sequence of the MDV2 UL10 gene with the homologues from other herpesviruse s, the data might contribute for further evidence of the evolution of herpe sviruses from a common progenitor and an ancient example of MDV2 belonging to the Alphaherpesvirinae subfamily. In addition, the existence of correspo nding genes in human, mammalian, and avian herpesvirus genomes, suggests in directly an important role for gM in the natural life cycle of the virus.