Transcriptional and translational expression kinetics of the UL25 homologue of bovine herpesvirus 1.1

We investigated whether the bovine herpesvirus 1.1 (BHV1) ORF, a homologue of the herpes simplex virus I (HSV 1) UL25 gene, represented a functional g ene. The BHV1 UL25 ORF, which is located at positions 60602 <-- 62398 of th e viral genome, generated a 4.5 kb transcript accumulating at low abundance as soon as 3 hours p.i. after which the levels increased up to 12 h p.i. a nd remained constant up to 24 hours p.i. In addition, UL25 transcription in itiated at 303 bases upstream from the translation initiation codon, corres ponding to 26 and 354 b downstream from putative TATA and CAAT boxes, respe ctively, thus providing evidence that these elements function as the UL25 p romoter. Western blotting of BHV1-infected cell lysates, using a BHV1-UL25 specific antiserum generated against a T7-Tag/UL25 fusion recombinant prote in expressed in E. coli, detected a 63 kDa protein of the expected size (63 ,083 Da) whose expression profile followed that of its transcript. The synt hesis of the 63 kDa protein was abrogated by a DNA synthesis inhibitor, una mbiguously demonstrating that the viral specific protein expressed from the BHV1 UL25 ORF belongs to the gamma2 class.