Identification and DNA sequence analysis of the Marek's disease virus serotype 2 genes homologous to the herpes simplex virus type 1 UL20 and UL21

We determined 3,135 bp of the nucleotide sequence located in an 8.5 kb EcoR I-E fragment in the unique long (UL) genome region of Marek's disease virus serotype 2 (MDV2), and identified UL20 and UL21 homologous genes of herpes simplex virus type 1 (HSV-1). The UL20 and UL21 homologous genes of MDV2 a re arranged colinearly with the prototype sequence of HSV-I. In addition, a n open reading frame (MDV2 ORF 273), which has been identified within the U L21 homologous gene of MDV2, has no apparent relation to any other known he rpesvirus genes. Northern blot analysis and reverse transcriptase polymeras e chain reaction confirmed the existance of RNA transcripts related to the UL20 and ORF 273 genes in MDV2-infected cells, except no transcript related to the UL21 gene being detected. The putative protein product of the MDV2 UL20 gene had a relatively low homology but that of the MDV2 UL21 gene had a moderate homology among herpesviruses. Further, the possible functions an d features of the predicted proteins encoded within the sequenced region ar e discussed.