A new crucial protein interaction element that targets the adenovirus E4-ORF1 oncoprotein to membrane vesicles.
Human adenovirus type 9 exclusively elicits mammary tumors in experimental animals, and the primary oncogenic determinant of this virus is the E4-ORF1 oncogene, as opposed to the well-known E1A and E1B oncogenes. The tumorigenic potential of E4-ORF1, as well as its ability to oncogenically stimulate phosphatidylinositol 3-kinase (PI3K), depends on a carboxyl-terminal PDZ domain-binding motif (PBM) that mediates interactions with several different membrane-associated cellular PDZ proteins, including MUPP1, PATJ, MAGI-1, ZO-2, and Dlg1. Nevertheless, because certain E4-ORF1 mutations that alter neither the sequence nor the function of the PBM abolish E4-ORF1-induced PI3K activation and cellular transformation, we reasoned that E4-ORF1 must possess an additional crucial protein element. In the present study, we identified seven E4-ORF1 amino acid residues that define this new element, designated domain 2, and showed that it mediates binding to a 70-kDa cellular phosphoprotein. We also discovered that domain 2 or the PBM independently promotes E4-ORF1 localization to cytoplasmic membrane vesicles and that this activity of domain 2 depends on E4-ORF1 trimerization. Consistent with the latter observation, molecular-modeling analyses predicted that E4-ORF1 trimerization brings together six out of seven domain 2 residues at each of the three subunit interfaces. These findings importantly demonstrate that PI3K activation and cellular transformation induced by E4-ORF1 require two separate protein interaction elements, domain 2 and the PBM, each of which targets E4-ORF1 to vesicle membranes in cells.
Chung
Sang-Hyuk
SH
Department of Molecular Virology and Microbiology, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA.
Frese
Kristopher K
KK
Weiss
Robert S
RS
Prasad
B V Venkataram
BV
Javier
Ronald T
RT
D017504:Adenovirus E4 Proteins / Q000235:genetics* / Q000378:metabolism*; D000260:Adenoviruses, Human / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D019295:Computational Biology; D022162:Cytoplasmic Vesicles / Q000378:metabolism* / Q000821:virology; D006801:Humans; D015151:Immunoblotting; D047468:Immunoprecipitation; D051379:Mice; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016296:Mutagenesis; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary / Q000235:genetics; D021381:Protein Transport / Q000502:physiology
D017504:Adenovirus E4 Proteins; D019869:Phosphatidylinositol 3-Kinases