A gamma-2 herpesvirus nucleocytoplasmic shuttle protein interacts with importin alpha 1 and alpha 5.
Herpesvirus saimiri (HVS) is the prototype gamma-2 herpesvirus. This is an increasing important subfamily of herpesviruses due to the identification of the first human gamma-2 herpesvirus, Kaposi's sarcoma-associated herpesvirus. The HVS open reading frame (ORF) 57 protein is a multifunctional trans-regulatory protein homologous to genes identified in all classes of herpesviruses. Recent analysis has demonstrated that ORF 57 has the ability to bind viral RNA and to shuttle between the nucleus and cytoplasm, and is required for efficient nuclear export of viral transcripts. Here we have investigated the nucleocytoplasmic shuttling mechanism utilized by the ORF 57 protein. The yeast two-hybrid system was employed to identify interacting cellular proteins using ORF 57 as bait. We demonstrate that ORF 57 interacts with importin alpha isoforms 1 and 5. In addition, the binding of ORF 57 to importin alpha was mediated by the importin alpha hydrophobic internal armadillo repeats. An ORF 57 amino-terminal arginine-rich sequence, which functions as a nuclear localization sequence, was also required for this interaction. Furthermore, the ORF 57 protein is responsible for the redistribution of importin alpha into the nucleoli. These results identify novel cellular interactions essential for the functioning of this important herpesvirus regulatory protein.
Molecular Medicine Unit, University of Leeds, St. James's University Hospital, Leeds LS9 7TF, United Kingdom.
D J
DJ
Goodwin
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A
Whitehouse
D000595:Amino Acid Sequence; D000818:Animals; D001120:Arginine / Q000378:metabolism; D019556:COS Cells; D006567:Herpesvirus 2, Saimiriine / Q000378:metabolism*; D028884:Karyopherins; D008969:Molecular Sequence Data; D019913:Nuclear Localization Signals; D009687:Nuclear Proteins / Q000378:metabolism*; D016366:Open Reading Frames; D011233:Precipitin Tests; D011485:Protein Binding; D012097:Repressor Proteins / Q000737:chemistry / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D015534:Trans-Activators / Q000737:chemistry / Q000378:metabolism*; D020798:Two-Hybrid System Techniques; D014764:Viral Proteins
D028884:Karyopherins; D019913:Nuclear Localization Signals; D009687:Nuclear Proteins; C415247:ORF57 protein, Herpesvirus saimiri; D012097:Repressor Proteins; D015534:Trans-Activators; D014764:Viral Proteins; D001120:Arginine