A putative NES mediates cytoplasmic localization of Apoptin in normal cells.
Apoptin, a protein expressed by chicken anemia virus, is found predominantly in the cytoplasm in normal cells, whereas it localizes in the nucleus in transformed and malignant cells. However, the mechanisms that regulate the different subcellular localization of Apoptin in normal and tumor cells have not been fully clarified. In this work, a putative nuclear export signal (NES) in Apoptin was predicted. It was testified that the putative NES (pNES) of Apoptin was not a functional NES, but actually acted as a cytoplasmic retention signal. Deletion of the pNES led to the nuclear accumulation of Apoptin in normal cells. In addition, when a strong nuclear localization signal was introduced into Apoptin, it exclusively translocated to the nucleus in normal cells. These observations indicated that the cytoplasmic localization of Apoptin in normal cells results from the balance between cytoplasmic retention and nuclear import. On the other hand, the pNES was also proved to be necessary for Apoptin multimerization. Mutants lacking the pNES did not form obviously visible globular aggregates in normal or tumor cells.
Wang
Qing-Ming
QM
Department of Genomics and Proteomics, Beijing Institute of Radiation Medicine, Beijing 100850, China. wang6801@yahoo.com
Fan
Guo-Cai
GC
Chen
Ji-Zhong
JZ
Chen
Hui-Peng
HP
He
Fu-Chu
FC
D021581:Active Transport, Cell Nucleus / Q000502:physiology*; D000595:Amino Acid Sequence; D000818:Animals; D036022:Capsid Proteins / Q000378:metabolism*; D002478:Cells, Cultured; D003593:Cytoplasm / Q000378:metabolism*; D017353:Gene Deletion; D022781:Hepatocytes / Q000378:metabolism; D008969:Molecular Sequence Data; D019913:Nuclear Localization Signals / Q000235:genetics / Q000502:physiology*; D020836:Protein Structure, Quaternary; D051381:Rats; D014162:Transfection
D036022:Capsid Proteins; D019913:Nuclear Localization Signals; C091717:VP3 protein, Chicken anemia virus