A new crucial protein interaction element that targets the adenovirus E4-ORF1 oncoprotein to membrane vesicles

J Virol. 2007 May;81(9):4787-97. doi: 10.1128/JVI.02855-06. Epub 2007 Feb 21.


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.

Publication types

  • Comparative Study
  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Adenovirus E4 Proteins / genetics*
  • Adenovirus E4 Proteins / metabolism*
  • Adenoviruses, Human / genetics
  • Adenoviruses, Human / metabolism*
  • Amino Acid Sequence
  • Animals
  • Cell Line
  • Computational Biology
  • Cytoplasmic Vesicles / metabolism*
  • Cytoplasmic Vesicles / virology
  • Humans
  • Immunoblotting
  • Immunoprecipitation
  • Mice
  • Models, Molecular*
  • Molecular Sequence Data
  • Mutagenesis
  • Phosphatidylinositol 3-Kinases / metabolism
  • Protein Binding
  • Protein Structure, Tertiary / genetics
  • Protein Transport / physiology


  • Adenovirus E4 Proteins
  • Phosphatidylinositol 3-Kinases