GENE ORGANIZATION IN HERPESVIRUS OF TURKEYS - IDENTIFICATION OF A NOVEL OPEN READING FRAME IN THE LONG UNIQUE REGION AND A TRUNCATED HOMOLOG OF PP38 IN THE INTERNAL REPEAT

The DNA sequence of a 4.792-kb fragment comprising 3.176 kb of the lon g unique region (U-L) and 1.605 kb of the internal repeat (IR(L)) flan king U-L of herpesvirus of turkeys (HVT) was determined. Three potenti al open reading frames (ORFs) and an origin of replication have been i dentified. ORF 1, which maps entirely within U-L, has the capacity to code for an 82K protein, 731 amino acids long, which has a counterpart in Marek's disease virus (MDV) but not in other herpesviruses. ORF 2 has the potential to encode a protein consisting of 129 amino acids wi th a predicted M(r) of 13.5K which appears to be unique to HVT. ORF 3 is encoded entirely within IR(L) and codes for an 84 amino acids long protein with a predicted M(r) of 8.5K. ORF 3 shows significant homolog y with the C-terminal region of the MDV-1-specific phosphoprotein pp38 and its recently identified homologue in MDV-2. Northern blot analysi s of RNA extracted from HVT-infected chick embryo fibroblasts identifi ed a 5.6-kb RNA transcribed in a leftward direction toward U-L spannin g ORF 1, ORF 2, and ORF 3 and a 2.8-kb also transcribed leftward towar d U-L which spanned only ORFs 2 and 3. In addition, a 2.3- to 2.8-kb R NA family was transcribed rightwards through the origin of replication . In vitro transcription and translation of ORF 1 and ORF 3 resulted i n the synthesis of polypeptides consistent with their expected M(r), b ut ORF 2 failed to produce any translation product. (C) 1995 Academic Press, Inc.