INSERTION OF A BOVINE SMT3B GENE IN NS4B AND DUPLICATION OF NS3 IN A BOVINE VIRAL DIARRHEA VIRUS GENOME CORRELATE WITH THE CYTOPATHOGENICITY OF THE VIRUS

Bovine viral diarrhea virus (BVDV) infection in cattle can lead to the development of a fatal syndrome called mucosal disease (MD). The indu ction of MD requires co-existence of two biotypes of BVDV: cytopathic (cp) and non-cytopathic (ncp). Studies have shown that in some cases; cp viruses are generated from ncp viruses by cellular gene insertions, duplications or rearrangements in the viral genome. Cellular ubiquiti n gene is the most frequently reported insert in BVDV 1. Here we repor t the finding of a novel cellular gene insertion (termed cSNCINS) in t he NS4B gene accompanied by the duplication of NS3 in a cpBVDV genome. The amino acid sequence of the insert is identical to that of the hum an SMT3B protein and is 98% similar to that of the human SMT3A protein . Both SMT3B and SMT3A proteins are homologues of the yeast SMT3 prote in. The cSNCINS protein is encoded by an open reading frame located on a 1150-bp bovine endometrial cDNA fragment. Our results indicate that the cSNCINS is a bovine homologue of the human SMT3B gene and that in sertion of the BSMT3B gene together with duplication of NS3 in the vir al genome may account for the cytopathogenicity of this virus. (C) 199 8 Elsevier Science B.V. All rights reserved.