Nuclear export of adenovirus E4orf6 protein is necessary for its ability to antagonize apoptotic activity of BH3-only proteins.
The adenovirus E4orf6 is a viral oncoprotein known to cooperate with the E1A gene product in transforming primary murine cells. It has been shown to inhibit the apoptotic activities of p53 and p73 through direct binding to these proteins. Here, we demonstrate that the adenovirus E4orf6 protein inhibits apoptosis mediated by BNIP3 and Bik, which are BH3-only proteins of the Bcl-2 family. This activity was not mediated by p53 and p73 because E4orf6 had the same effect on the apoptosis in Saos-2 cells that do not express p53-related genes. It was also ascertained that E4orf6 could change the mitochondrial localization of BNIP3 and Bik. A mutant lacking the nuclear export signal of E4orf6 failed to inhibit apoptosis and to translocate BNIP3 protein from the mitochondria. Moreover, it was also established that E4orf6 was able to interact with BNIP3 and Bik. In BNIP3 protein, the region required for the interaction included the transmembrane domain, which is required for the localization of BNIP3 to the mitochondria. These results suggest that E4orf6 is exported from the nucleus to the cytoplasm, enabling it to interact with BH3-only proteins, eventually leading to the inhibition of apoptotic activity.
Aoyagi
Mariko
M
Department of Oral Pathobiological Science, Hokkaido University Graduate School of Dental Medicine, N13, W7, Kita-ku, Sapporo 060-8586, Japan.
Higashino
Fumihiro
F
Yasuda
Motoaki
M
Takahashi
Akiko
A
Sawada
Yukiharu
Y
Totsuka
Yasunori
Y
Kohgo
Takao
T
Sano
Hidehiko
H
Kobayashi
Masanobu
M
Shindoh
Masanobu
M
D021581:Active Transport, Cell Nucleus; D017504:Adenovirus E4 Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D020816:Amino Acid Motifs; D019943:Amino Acid Substitution; D000818:Animals; D017209:Apoptosis; D051017:Apoptosis Regulatory Proteins; D019556:COS Cells; D002467:Cell Nucleus / Q000378:metabolism*; D002478:Cells, Cultured; D002522:Chlorocebus aethiops; D016384:Consensus Sequence; D017124:Conserved Sequence; D008564:Membrane Potentials; D008565:Membrane Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism; D008928:Mitochondria / Q000378:metabolism; D024101:Mitochondrial Proteins; D016297:Mutagenesis, Site-Directed; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011506:Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D011518:Proto-Oncogene Proteins; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D015398:Signal Transduction; D013347:Subcellular Fractions / Q000378:metabolism; D025521:Tumor Suppressor Proteins
D017504:Adenovirus E4 Proteins; D051017:Apoptosis Regulatory Proteins; C096820:BIK protein, human; C090121:BNIP3 protein, human; C116838:BNIP3L protein, human; D008565:Membrane Proteins; D024101:Mitochondrial Proteins; D011506:Proteins; D011518:Proto-Oncogene Proteins; D011993:Recombinant Fusion Proteins; D025521:Tumor Suppressor Proteins