Identification and analysis of the K5 gene of Kaposi's sarcoma-associated herpesvirus.

Abstract

Kaposi's sarcoma-associated herpesvirus (KSHV), or human herpesvirus 8 (HHV-8), belongs to the gammaherpesvirus subfamily and encodes approximately 80 open reading frames (ORFs). Among them are a few candidates for immediate-early genes (e.g., K5). We developed a monoclonal antibody (MAb), 328C7, against the K5 antigen. This MAb reacted with the K5 gene product by immunoscreening of a cDNA library from BCBL-1 cells, and this result was confirmed by transfection of the K5 ORF into Cos-7 cells. After induction of lytic infection by treatment with 12-O-tetradecanoylphorbol-13-acetate, MAb 328C7 reacted with an antigen in the cytoplasm of BCBL-1 and BC-3 cells as early as after 4 h of induction. Immunoelectron microscopy showed that the K5 antigen was situated mainly in the endoplasmic reticulum but was not present on the virion or in the nucleus. Northern blotting with a K5-specific probe revealed a single transcript of 1.2 kb, while Western blotting showed the antigen to be a 36-kDa polypeptide. The 5' and 3' ends were then determined by rapid amplification of cDNA, followed by sequencing of RACE products, and a splice was revealed upstream of the K5 ORF. K5 expression was unaffected by the respective DNA and protein synthesis inhibitors phosphonoformic acid and cycloheximide plus actinomycin D, confirming its immediate-early nature. Transient-transfection assays showed that the K5 promoter was transactivated by ORF 50 (KSHV Rta), a homolog of Epstein-Barr virus Rta, but the K5 gene product exhibited no transregulation of its own promoter or those of DNA polymerase and the human immunodeficiency virus type 1 long terminal repeat. This is the first such analysis of an immediate-early gene product; determination of its specific biological function requires further investigation.

• Authors: M Haque, J Chen, K Ueda, Y Mori, K Nakano, Y Hirata, S Kanamori, Y Uchiyama, R Inagi, T Okuno, K Yamanishi
• Journal: Journal of virology (J Virol) Vol. 74 Issue 6 Pg. 2867-75 (Mar 2000) ISSN: 0022-538X [Print] United States
• PMID: 10684303 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Antibodies, Monoclonal
• Antibodies, Viral
• DNA, Viral
• Immediate-Early Proteins
• K5 protein, Human herpesvirus 8
• Viral Proteins

Topics

• Animals
• Antibodies, Monoclonal (immunology)
• Antibodies, Viral (immunology)
• Base Sequence
• Blotting, Western (methods)
• COS Cells
• Cell Line
• DNA, Viral
• Gene Expression Regulation, Viral
• Genes, Viral
• Herpesvirus 8, Human (genetics)
• Humans
• Immediate-Early Proteins (genetics, immunology)
• Molecular Sequence Data
• Transcription, Genetic
• Viral Proteins (genetics, immunology)