N. Kudo et al., A novel nuclear export signal sensitive to oxidative stress in the fissionyeast transcription factor Pap1, J BIOL CHEM, 274(21), 1999, pp. 15151-15158
Pap1, a fission yeast AP-l-like transcription factor, is negatively regulat
ed by CRM1/exportin 1, the nuclear export factor. Pap1 was localized normal
ly in the cytoplasm but was accumulated in the nucleus when Crm1 was inacti
vated by a temperature sensitive mutation or by treatment with leptomycin B
, a specific export inhibitor. Deletion of the C-terminal cysteine-rich dom
ain (CRD) resulted in nuclear accumulation of Pap1, while a glutathione S-t
ransferase-green fluorescent protein-CRD fusion protein was localized in th
e cytoplasm in a Crm1-dependent manner. Deletion and mutational analyses id
entified several important amino acids in a 19-amino acid region in the CRD
as a nuclear export signal (NES), Strikingly, a cysteine residue (Cys-532)
, in addition to two leucines and an isoleucine, was important for the NES
function and the presence of at least one of the two cysteine residues was
essential. Unlike classical NESs such as the human immunodeficiency virus R
ev NES, the Pap1 NES lost the function upon treatment with oxidants such as
diethyl maleate. The oxidative stress response is conserved through evolut
ion, as green fluorescent protein-fused proteins bearing the Pap1 NES expre
ssed in mammalian cells responded to diethyl maleate. These results show th
at the hydrophobic amino acid-rich region containing two important cysteine
s in Pap1 serves as a novel NES, which is sensitive to oxidative stress.