Bovine Herpes Virus 1 Major Immediate Early Transcription Unit 1 (IETU-1) Uses Alternative Promoters to Transcribe BICP0 and BICP4 Transcripts

Abstract

Immediate early (IE) genes are transcribed immediately after infection in BHV1 from two different immediate early transcription units. It is reported that the immediate early transcription unit I (IE TU1) of Bovine herpesvirus 1 (BHV1) transcribes two proteins BICP0 and BICP4 from a single promoter by alternative splicing but with identical 5'UTR. We found that the transcripts of BICP0 and BICP4 have different 5'UTRs. The bioinformatics analysis shows two similar spatially arranged TATA less promoter for the two transcripts. The bioinformatics analysis also showed a similar promoter for the IE TU2 which transcribes BICP22. The data strongly suggest that BICP0 and BICP4 are transcribed from two different promoters. The transcript produced by each promoter is spliced specifically as opposed to what has been reported earlier. The BICP0 and BICP4 also show different levels of expression. The expression level of BICP4 continuously declines after attaining a peak level at 1 h, while BICP0 shows biphasic expression supporting the earlier observation that it is expressed from two different promoters.

Three newly identified Immediate Early Genes of Bovine herpesvirus 1 lack the characteristic Octamer binding motif- 1

“…There are reports showing that C/EBPα can transactivate IE genes of BoHV-1 25 , 37 – 39 , in vitro and also that bTIF can activate promoters that lack OCT-1 motifs provided an alternate mechanism for DNA binding is available 10 . We recently reanalyzed the promoters of known IE gene of BoHV-1 9 and observed that instead of two 4 , 5 , 40 , there are three IE transcription units and each of the transcription units have similarly placed INR, DPE and OCT-1 motifs thus reinforcing the hypothesis of OCT-1 having a role in the transactivation of IE genes in BoHV-1.…”

“…2A–C ) suggesting one TSS for each gene. The BICP0, BICP4 and BICP22 also have one transcription start site 9 . The distance between TSS and putative translation start site (ATG) varied among these three genes.…”

“…These BICP genes are counterparts to infected cell proteins (ICP) 0, 4 and 22 of HHV-1 7 . The IE transcripts are grouped under two divergent IE transcription unit (IETU); IE4.2 and IE2.9 belongs to IETU1 and IE1.7 comes under IETU2 4 , 5 , 8 but recently it has been shown that BICP0, BICP4 and BICP22 are transcribed from three independent transcription units 9 .…”