http://www.abbs.info E-mail: [email protected]
ISSN
1672-9145
Acta Biochim Biophys Sin 2004,
36(12): 817–823
CN 31-1940/Q
A Putative NES Mediates Cytoplasmic Localization of Apoptin in Normal Cells
Qing-Ming WANG*, Guo-Cai
FAN, Ji-Zhong CHEN, Hui-Peng CHEN, and Fu-Chu
HE*
Department of Genomics and Proteomics, Beijing Institute of Radiation Medicine, Beijing 100850, China
Abstract 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.
Key words Apoptin; nuclear
localization signal; cytoplasmic retention signal; nuclear export signal
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Received: September 14, 2004 Accepted: October 18, 2004
*Corresponding authors:
Qing-Ming WANG: Fax, 86-10-68214653; E-mail, [email protected]
Fu-Chu HE: E-mail, [email protected]