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

Summary.

  We investigated whether the bovine herpesvirus 1.1 (BHV1) ORF, a homologue of the herpes simplex virus 1 (HSV1) UL25 gene, represented a functional gene. The BHV1 UL25 ORF, which is located at positions 60602 ← 62398 of the 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. and remained constant up to 24 hours p.i. In addition, UL25 transcription initiated at 303 bases upstream from the translation initiation codon, corresponding to 26 and 354 b downstream from putative TATA and CAAT boxes, respectively, thus providing evidence that these elements function as the UL25 promoter. Western blotting of BHV1-infected cell lysates, using a BHV1-UL25 specific antiserum generated against a T7-Tag/UL25 fusion recombinant protein 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 synthesis of the 63 kDa protein was abrogated by a DNA synthesis inhibitor, unambiguously demonstrating that the viral specific protein expressed from the BHV1 UL25 ORF belongs to the γ2 class.