Identification and characterization of BICP27, an early protein of bovine herpesvirus 1 which may stimulate mRNA 3' processing.

Sequence analysis of the left genomic terminus of bovine herpesvirus 1 (BHV-1) revealed two convergently transcribed genes with 3' ends about 300 bp apart. The gene on the left is the previously described circ gene; that on the right was found to encode a protein of 400 amino acids which was designated BICP27 because of its homology to ICP27 (Vmw63) of herpes simplex virus 1 (HSV-1) and related proteins from other alpha- beta- and gammaherpesviruses. Rabbit antisera raised against a synthetic oligopeptide representing the amino terminus of the predicted polypeptide demonstrated the presence of BICP27 in the nuclei of infected cells by in situ immunoadsorbent assays. In Western immunoblots, BICP27 was detected as a 50 kDa BHV-1 specific protein expressed with early kinetics, in contrast to HSV-1 ICP27 which is an immediate early (IE) protein. A DNA fragment containing BICP27 coding sequences was inserted into a baculovirus genome. The recombinant BICP27 protein, identified by its reactivity with the antipeptide sera, exhibited the same electrophoretic mobility as BICP27 specified by BHV-1. Transient expression assays using target genes differing only in their poly(A) sites showed that BICP27, like its HSV-1 counterpart, may be involved in 3' processing of mRNA.