Similar regulation of two distinct UL24 promoters by regulatory proteins of equine herpesvirus type 1 (EHV-1)

To characterise the pattern of the transcriptional regulation of equine herpesvirus type 1 (EHV-1) UL24 by regulatory proteins, we identified two distinct promoter regions and two transcription initiation (Tci) sites located upstream of the UL24 open reading frame (ORF). The ORF proximal promoter exhibited higher cis-activity than that of the distal one. Contrary to the former, the latter performed its function dependent on an initiator (INR) due to its lack of a TATA box. Our results showed that the EHV-1 regulatory proteins EICP0, EICP22 and ETIF trans-activated the two promoters, whereas IEP and IR2P displayed negative regulation. In summary, the regulatory proteins exhibited similar regulatory patterns for the two distinct promoters of EHV-1 UL24.