Importance of nuclear localization of apoptin for tumor-specific induction of apoptosis.
The chicken anemia virus-derived protein Apoptin induces apoptosis specifically in human tumor and transformed cells and not in normal, untransformed cells. The cell killing activity correlates with a predominantly nuclear localization of Apoptin in tumor cells, whereas in normal cells, it is detected mainly in cytoplasmic structures. To explore the role of nuclear localization for Apoptin-induced cell death in tumor cells, we employed a mutagenesis strategy. First, we demonstrated that the C terminus of Apoptin contains a bipartite-type nuclear localization signal. Strikingly, further investigation showed that Apoptin contains two different domains that induce apoptosis independently, and for both domains, we found a strong correlation between localization and killing activity. Using inhibitors, we ruled out the involvement of de novo gene transcription and translation and further showed that Apoptin itself does not have any significant transcriptional repression activity, suggesting that Apoptin exerts its effects in the nucleus by some other method. To determine whether nuclear localization is sufficient to enable Apoptin to kill normal, untransformed cells, we expressed full-length Apoptin fused to a heterologous nuclear localization signal in these cells. However, despite its nuclear localization, no apoptosis was induced, which suggests that nuclear localization per se is not sufficient for Apoptin to become active. These studies increase our understanding of the molecular pathway of Apoptin and may also shed light on the mechanism of cellular transformation.
Danen-Van Oorschot
Astrid A A M
AA
Leadd BV, 2300 RA Leiden, The Netherlands.
Zhang
Ying-Hui
YH
Leliveld
S Rutger
SR
Rohn
Jennifer L
JL
Seelen
Maud C M J
MC
Bolk
Marian W
MW
Van Zon
Arend
A
Erkeland
Stefan J
SJ
Abrahams
Jan-Pieter
JP
Mumberg
Dominik
D
Noteborn
Mathieu H M
MH
D021581:Active Transport, Cell Nucleus; D000595:Amino Acid Sequence; D017209:Apoptosis; D002213:Capsid / Q000737:chemistry / Q000378:metabolism*; D036022:Capsid Proteins; D002460:Cell Line; D002461:Cell Line, Transformed; D002467:Cell Nucleus / Q000378:metabolism* / Q000648:ultrastructure; D002471:Cell Transformation, Neoplastic; D003593:Cytoplasm / Q000378:metabolism; D005347:Fibroblasts / Q000378:metabolism; D017930:Genes, Reporter; D006801:Humans; D008156:Luciferases / Q000378:metabolism; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D009154:Mutation; D019913:Nuclear Localization Signals; D010957:Plasmids / Q000378:metabolism; D014176:Protein Biosynthesis; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid; D014158:Transcription, Genetic; D014162:Transfection; D014407:Tumor Cells, Cultured
D036022:Capsid Proteins; D019913:Nuclear Localization Signals; C091717:VP3 protein, Chicken anemia virus; D008156:Luciferases