The Herpesvirus Saimiri open reading frame 73 gene product interacts with the cellular protein p32.
The role of the gamma-2 herpesvirus open reading frame (ORF) 73 gene product has become the focus of considerable interest. It has recently been shown that the Kaposi's sarcoma-associated herpesvirus (KSHV) latency-associated nuclear antigen (LANA) is expressed during a latent infection and can modulate both viral and cellular gene expression. The herpesvirus saimiri (HVS) ORF 73 gene product has some sequence homology to LANA; however, the role of HVS ORF 73 is unknown. We have previously demonstrated that HVS ORF73 is expressed in a stably transduced human carcinoma cell line, where HVS genomes persist as nonintegrated circular episomes. This implies that there may be some functional homology between these proteins. To further investigate the role of the HVS ORF 73 protein, the yeast two-hybrid system was employed to identify interacting cellular proteins. We demonstrate that ORF 73 interacts with the cellular protein p32 and triggers the accumulation of p32 in the nucleus. Using reporter gene-based transient-transfection assays, we demonstrate that ORF 73 can transactivate a number of heterologous promoter constructs and also upregulate its own promoter. Moreover, ORF 73 and p32 act synergistically to transactivate these promoters. The binding of ORF 73 to p32 is mediated by an amino-terminal arginine-rich domain, which contains two functionally distinct nuclear localization signals. The p32 binding domains are required for ORF 73 transactivating abilities and for ORF 73 to induce nuclear accumulation of p32. These results suggest that ORF 73 can function as a regulator of gene expression and that p32 is involved in ORF 73-dependent transcriptional activation.
Hall
Kersten T
KT
Institute of Cardiovascular Research, University of Leeds, Leeds LS2 9JT, United Kingdom.
Giles
Mathew S
MS
Calderwood
Michael A
MA
Goodwin
Delyth J
DJ
Matthews
David A
DA
Whitehouse
Adrian
A
D000595:Amino Acid Sequence; D000818:Animals; D019556:COS Cells; D002352:Carrier Proteins; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D005786:Gene Expression Regulation; D006567:Herpesvirus 2, Saimiriine / Q000235:genetics / Q000378:metabolism*; D024101:Mitochondrial Proteins; D008969:Molecular Sequence Data; D019913:Nuclear Localization Signals / Q000737:chemistry; D009687:Nuclear Proteins / Q000378:metabolism*; D016366:Open Reading Frames / Q000235:genetics / Q000502:physiology*; D015534:Trans-Activators / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015533:Transcriptional Activation; D014162:Transfection; D020798:Two-Hybrid System Techniques; D014764:Viral Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
C087299:C1QBP protein, human; D002352:Carrier Proteins; D024101:Mitochondrial Proteins; D019913:Nuclear Localization Signals; D009687:Nuclear Proteins; D015534:Trans-Activators; D014764:Viral Proteins