| Research Abstract |
Yap1 is AP-1 like transcript ion factor of the budding yeast, S. cerevisiae. Yap1 is a crucial and essential transcription factor for the oxidative stress response. We have shown previously that Yap1 mainly exists in the cytoplasm, however, Yap1 localized in the nucleus in response to oxidative stress.
In this research project, we aim to show that the mechanism of the regulation of nucleo-cytoplasmic transport of Yap1. Firstly, we showed that Yap1 is imported by one of the multiple import receptors (importin), Pse1, which is shown to be import receptor for unrelated transcription factor Pho4. On the other hand, Yap I is exported by nuclear export receptor (exportin) Crm1 that recognizes the nuclear export signal (NES). Therefore, Yap1 shuttles between the cytoplasm and nucleus. The nuclear export contributes lower concentration of Yap1 in the nucleus, and thus the lower activity of target gene transcription. Interestingly, our data indicates that oxidative stress inhibits ,the interaction between Yap1 and the Crm1.
Secondly, CRD (C-terminal cysteine-rich domain of Yap1, appears to be essential domain for Crm1-dependent nuclear export, indicating that CRD acts as a NES. The CRD contains NES-like hydrophobic cluster as well as unique three cysteine residues, one in the middle of NES-like region. When all three cysteine residues are mutated to Thr or Ala. CRD can act as NES, however, no more oxidative stress response was observed.
Thirdly, we showed that cysteine residues in the CRD appear to be oxidized to disulfide and form CRD-CRD homo-dimer. These suggest that the CRD cysteine residues are redox regulated, and the NES activity might be inhibited by the disulfide formation.
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