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J. Virol., Oct 1997, 7873-7880, Vol 71, No. 10
RS Weiss and RT Javier
Human adenovirus type 9 (Ad9) is unique among oncogenic adenoviruses in
that it elicits exclusively mammary tumors in rats and requires the viral
E4 region open reading frame 1 (9ORF1) gene for tumorigenicity. The 9ORF1
oncogenic determinant codes for a 14-kDa transforming protein, and three
separate regions of this polypeptide, including one at the extreme C
terminus, are necessary for transforming activity. In this study, we
investigated whether the 9ORF1 transforming protein interacts with cellular
factors. Following incubation with cell extracts, a glutathione
S-transferase (GST)-9ORF1 fusion protein associated with several cellular
phosphoproteins (p220, p180, p160, p155), whereas GST fusion proteins of
transformation-defective 9ORF1 C- terminal mutants did not. Similar
interactions requiring the 9ORF1 C terminus were revealed with
protein-blotting assays, in which a GST- 9ORF1 protein probe reacted
specifically with cellular polypeptides having gel mobilities resembling
those of the 9ORF1-associated cellular phosphoproteins, as well as with
additional cellular polypeptides designated p140/p130. In addition, GST
fusion proteins containing 9ORF1 C-terminal fragments associated with some
of the 9ORF1-associated cellular polypeptides, as did GST fusion proteins
of full-length wild- type Ad5 and Ad12 E4 ORF1 transforming proteins.
Significantly, the results of coimmunoprecipitation analyses suggested that
the same cellular polypeptides also associate with wild-type but not
C-terminal- mutant 9ORF1 proteins in vivo. Together, these findings suggest
that the 9ORF1 C terminus, which is essential for transformation,
participates in specific and direct binding of the 9ORF1 oncoprotein to
multiple cellular polypeptides. We propose that interactions with these
cellular factors may be responsible, at least in part, for the transforming
activity of the 9ORF1 viral oncoprotein.
Copyright © 1997, American Society for Microbiology
A carboxy-terminal region required by the adenovirus type 9 E4 ORF1 oncoprotein for transformation mediates direct binding to cellular polypeptides
Division of Molecular Virology, Baylor College of Medicine, Houston, Texas 77030, USA.
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