Two nuclear export signals specify the cytoplasmic localization of calcineurin B homologous protein 1.
We previously showed that calcineurin B homologous protein 1 (CHP1) interacts with nuclear apoptosis-inducing protein kinase DRAK2, and that overexpression of DRAK2 induces the nuclear accumulation of CHP1, although CHP1 usually resides in the cytoplasm [Matsumoto et al. (2001) J. Biochem. 130, 217-225]. Here we show that CHP1 has two functional nuclear export signal (NES) sequences in its carboxyl-terminal region. Treatment of several cell lines with leptomycin B, a specific inhibitor of CRM1-dependent nuclear export, induces the nuclear accumulation of CHP1. Moreover, CHP1-GFP fusion proteins with deletions or point mutations affecting the two putative NES sequences accumulate in the nucleus to a greater extent than wild-type CHP1-GFP. Tagging glutathione S-transferase-GFP fusion protein with each NES sequence caused a shift in their intracellular localization from all over the cells to the cytoplasm. These results suggest that after CHP1 has entered the nucleus, it is exported to the cytoplasm in an NES-dependent manner.
Nagita
Mana
M
Department of Biological Sciences, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043.
Inoue
Hiroki
H
Nakamura
Norihiro
N
Kanazawa
Hiroshi
H
D021581:Active Transport, Cell Nucleus / Q000235:genetics; D000595:Amino Acid Sequence; D000818:Animals; D016466:CHO Cells; D019556:COS Cells; D019703:Calcineurin / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002135:Calcium-Binding Proteins / Q000032:analysis / Q000096:biosynthesis* / Q000235:genetics; D002467:Cell Nucleus / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002522:Chlorocebus aethiops; D006224:Cricetinae; D003593:Cytoplasm / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D049452:Green Fluorescent Proteins; D006801:Humans; D007424:Intracellular Fluid / Q000737:chemistry / Q000378:metabolism; D008164:Luminescent Proteins / Q000235:genetics; D051379:Mice; D008969:Molecular Sequence Data; D041681:NIH 3T3 Cells; D020033:Protein Isoforms / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D051381:Rats
C469743:CHP1 protein, human; D002135:Calcium-Binding Proteins; D008164:Luminescent Proteins; D020033:Protein Isoforms; D049452:Green Fluorescent Proteins; D019703:Calcineurin