| An origin of replication sequence was found in the inverted repeat regions of the bovine herpesvirus 1 genome (K22 and Cooper strains). The BHV1 oriS is located in the HindIII D fragment to the immediate left of the EcoRI site at map position 0.81. The 162 bp BHV1 oriS sequence was compared to HSV-1, HSV-2, EHV-1, and VZV origins. Homology is greatest to the HSV origins (52-54%), then EHV (49%), then VZV (35%). In the highly conserved 61 bp core region, homology to HSV is 71-73%, to EHV is 64%, and to VZV is 51%. The BHV1 oriS occurs as a 66 bp duplication, separated by 46 bp. Both origin copies contain the essential 9 bp sequence CGTTCGCAC and the alternating A-T repeat; there are 7 bp changes in the core region. Part of the sequence between the duplicated origins is homologous to the proposed HSV-1 UL9 binding site III (GTGAGAACGC). Since EHV-1 and VZV origin sequences are reported not to contain site III, here again BHV1 shows a closer relationship to the herpes simplex viruses.;Fine structure maps were constructed of the microheterogeneity regions in the Eco-Hin fragment to the right of the origin. Four areas of fragment length variation were found. These involve a repeating promoter region, both exon and intron regions of the IER1.7 gene, and a fragment spanning the junction of the inverted repeat and the unique short segment. Sequencing of the repeating promoter region revealed a short inverted repeat, part of which is also the same sequence identified as the site III binding site for the HSV origin binding protein. The significance of the presence of this common site in both the origin of replication and in the middle of a promoter region is not clear, but suggests possible recombinational or regulatory relationships. |
