Expression of the bovine papillomavirus type 1 E5B gene reveals a protein–protein interaction of the E5A and E5B gene products

• Published in: Virology (New York, N.Y.) N.Y.), 2003-03, Vol.307 (2), p.396-405
• Main Authors: Wlazlo, A.P, Sparkowski, J.J, Jenson, A.B, Schlegel, R
• Format: Article
• Language: English
• Subjects: 3T3 Cells; Animals; Bovine papillomavirus 1 - genetics; Bovine papillomavirus type 1; COS Cells; E5A; E5B; Endoplasmic Reticulum - metabolism; Epitopes; Mice; Nuclear Envelope - metabolism; Oncogene Proteins, Viral - metabolism; Oncoprotein; Open Reading Frames; Transfection; Transformation; Viral Proteins - genetics; Viral Proteins - metabolism
• ISSN: 0042-6822; 1096-0341
• DOI: 10.1016/S0042-6822(02)00090-9

The bovine papillomavirus type 1 (BPV-1) genome has been shown to contain a small open-reading frame designated E5B (nucleotides 4013–4167) which is predicted to encode a hydrophobic, 52 amino acid protein. In order to detect and characterize the E5B protein, an 18 nucleotide sequence encoding a 6 amino acid epitope was added to the 3′ end of the E5B open-reading frame which was then expressed in COS-1 cells using a SV40 vector. Immunoprecipitation, immunofluorescence, and cell fractionation studies identified the E5B protein as a 4-kDa protein and localized it primarily to membranes of the endoplasmic reticulum and nucleus. Unlike the E5A protein of BPV-1, E5B did not form dimers (despite containing a cysteine residue) or form complexes with growth factor receptors such as the PDGF receptor or erb B-2 receptor. Interestingly, the E5B protein formed physical complexes with the hydrophobic E5A oncoprotein, apparently via transmembrane interactions. Additionally, expression of E5B inhibited the transforming capability of BPV-1 E5A. These observations suggest that the expression of this viral protein may play a significant role in BPV/host cell interactions.