The 357 amino acid open reading frame 1 (OFF-1), also designated DR7, within the SalI-L fragment of human herpesvirus 6 (HHV-6) exhibited transactivation of the human immunodeficiency virus type 1 (HIV-1) long terminal repeat (LTR) promoter and increased HIV-1 replication (Kashanchi et al., Virology, 201, 95-106, 1994). Tn the current study, the SalI-L transforming region was localized to the SalI-L-SH subfragment, Several ORFs identified in SalI-L-SH by sequence analysis were cloned into a selectable mammalian expression vector, pBK-CMV, Only pBK/ORF1 transformed NIH3T3 cells. Furthermore, cells expressing ORF-1 protein produced fibrosarcomas when injected into nude mice, whereas control cells, expressing either no ORF-1 protein or C-terminal truncated (after residue 172) ORF-1 protein, were not tumorigenic, Western blot analysis of proteins extracted from the tumors revealed ORF-1 protein. Additional studies indicated that ORF-1 was expressed in HHV-6-infected human T-cells by 18 h. Co-immunoprecipitation experiments showed that ORF-1 protein bound to tumor suppressor protein p53, and the OFF-1 binding domain on p53 was located between residues 28 and 187 of p53, overlapping with the specific DNA binding domain. Functional studies showed that p53-activated transcription was inhibited in ORF-1, but not in truncated OFF-1, expressing cells. Importantly, the truncated ORF-1 mutant also failed to cause transformation. Analysis of several human tumors by PCR revealed OFF-1 DNA sequences in some angioimmunoblastic lymphadenopathies, Hodgkin's and non-Hodgkin's lymphomas and glioblastomas. The detection of OFF-1 sequences in human tumors, while not proof per se, is a prerequisite for establishing its role in tumor development. Taken together, the results demonstrate that OFF-1 is an HHV-6 oncogene that binds to and affects p53. The identification of both transforming and transactivating activities within ORF-1 is a characteristic of other viral oncogenes and is the first reported for HHV-6.
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|Anno di pubblicazione:||1997|
|Titolo:||Human herpesvirus 6 (HHV-6) ORF-1 transactivating gene exhibits malignant transforming activity and its protein binds to p53|
|Autori:||F. Kashanchi; J. Araujo; J. Doniger; S. Muralidhar; R. Hoch; S. Khleif; E. Mendelson; J. Thompson; N. Azumi; JN Brady; M. Luppi; G. Torelli; LJ Rosenthal|
|Autori interni:||LUPPI, Mario |
|Appare nelle tipologie:||Articolo su rivista|
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