Identification and transcriptional analysis of the homologues of the herpes simplex virus type 1 UL30 to UL40 genes in the genome of nononcogenic Marek's disease virus serotype 2

Studies on Marek's disease virus serotype 2 (MDV2) are important for understanding the natural nononcogenic phenotype of MDV. This study reports a 27,535 bp nucleotide sequence of part of the MDV2 genome located in the central unique long (U(L)) region. The analysis revealed 11 complete ORFs with high amino acid sequence identities to the products of other alphaherpesviruses. The MDV2 ORFs were arranged collinearly with the prototype sequence of herpes simplex virus type 1, ranging from the UL30 to UL40 genes. Sequences that were particularly well conserved among alphaherpesviruses were the putative functional domain of the DNA polymerase (UL30) and the ribonucleotide reductase large and small subunits (UL39 and UL40). On the other hand, in contrast to oncogenic MDV1, MDV2 did not contain the conserved proline-repeat region in the UL36 homologue. All the genes identified were confirmed to be transcribed as 3'-coterminal mRNAs and/or unique transcripts in virus-infected cells.