The 41-kDa protein of human herpesvirus 6 specifically binds to viral DNA polymerase and greatly increases DNA synthesis.
We previously isolated a 41-kDa early antigen of human herpesvirus 6 (HHV-6), which exhibited nuclear localization and DNA-binding activity (Agulnick et al., 1993). In this study, we observed that a 110-kDa protein was coimmunoprecipitated with p41 from HHV-6-infected cells by an anti-p41 antibody. This 110-kDa protein was identified as the HHV-6 DNA polymerase (Pol-6) by an antibody raised against the N terminus of Pol-6. Reciprocal immunoprecipitation and Western blot analyses confirmed that p41 complexes with Pol-6 in HHV-6-infected cells. In addition, both p41 and Pol-6 were expressed in vitro and shown to form a specific complex. An in vitro DNA synthesis assay using primed M13 single-stranded DNA template demonstrated that p41 not only increased the DNA synthesis activity of Pol-6 but also allowed Pol-6 to synthesize DNA products corresponding to full-length M13 template (7249 nucleotides). By contrast, Pol-6 alone could only synthesize DNA of <100 nucleotides. The functional interaction between Pol-6 and p41 appears to be specific because they could not be physically or functionally substituted in vitro by their herpes simplex virus 1 homologues. Moreover, as revealed by mutational analysis, both the N and C termini of Pol-6 contribute to its binding to p41. In the case of p41, the N terminus is required for increasing DNA synthesis but not binding to Pol-6, whereas the C terminus is totally dispensable.
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School of Dental Medicine, School of Medicine, University of Pennsylvania, 4010 Locust Street, Philadelphia, Pennsylvania, 19104, USA.
Ricciardi
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D002460:Cell Line; D004279:DNA, Viral / Q000096:biosynthesis*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D004259:DNA-Directed DNA Polymerase / Q000235:genetics / Q000378:metabolism*; D015654:Herpesvirus 6, Human / Q000201:enzymology / Q000378:metabolism*; D006801:Humans; D011485:Protein Binding; D017384:Sequence Deletion; D013601:T-Lymphocytes / Q000821:virology; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism*
D004279:DNA, Viral; D004268:DNA-Binding Proteins; D014764:Viral Proteins; C081690:p41 protein, Human herpesvirus 6; D004259:DNA-Directed DNA Polymerase