The complete unique long sequence and the overall genomic organization of the GA strain of Marek's disease virus

We have determined the DNA sequence of the unique long (UL) region and the repeat long (RL) region in the genome of serotype 1 GA strain of Marek's di sease virus (MDV), a member of the alpha-herpesvirus family. With this info rmation, the complete nucleotide sequence of GA-MDV is now known, The entir e GA-MDV genome is predicted to be about 174 kbp in size, with an organizat ion of TRL-UL-IRL-IRS-US-TRS. typical of a alpha-herpesvirus. The UL sequen ce contains 113,508 bp and has a base composition of 41.7% G + C, A total o f 67 ORFs were identified completely within the UL region, among which 55 a re homologous to genes encoded by herpes simplex virus-1. Twelve of them ar e unique with presently unknown functions. The sequence of RL reported here together with those published earlier reveal the major structural features of the RL, Virtually all of the ORFs encoded by RL are specific to serotyp e I of MDV, These ORFs are likely to contribute to some of the unique biolo gical properties of MDV. Among the proteins encoded by MDV-specific ORFs ar e Meg, a jun/fos family of transcriptional factor implicated in transformat ion and latency, virus-encoded interleukin-8 a CXC chemokine, and pp38 and pp24, two phosphoproteins with undefined functions. There is also a putativ e lipase gene (LORF2) that has homologies in HPRS-24 (serotype II) strain o f MDV and in various avian adenoviruses. An additional unique feature of MD V is the presence of long terminal repeat remnant sequences of avian retrov irus reticuloendotheliosis virus. These remnant sequences are derived from the U3-enhancer region through ancestral insertions by reticuloendotheliosi s virus proviruses.