SUMO regulates the cytoplasmonuclear transport of its target protein Daxx.
It is known that Fas death domain-associated protein (Daxx) possesses both putative nuclear and cytoplasmic functions. However, the nuclear transport mechanism is largely unknown. This study examined the nuclear location signal (NLS) of Daxx and whether the nuclear transport of Daxx was mediated by small ubiquitin-related modifier (SUMO). Two NLS motifs of Daxx, leucine (L)-rich nuclear export signal (NES)-like motif (188IXXLXXLLXL197) and C-terminal lysine (K) rich NLS2 (amino acids 627-634) motif, were identified and the K630 and K631 on the NLS2 motif were characterized as the major sumoylation sites of Daxx by in vitro sumoylation analysis. Proteins of inactive SUMO (SUMO-delta), a sumoylation-incompetent mutant, and Daxx NLS mutants (Daxx-NES(mut) and Daxx NLS2(mut)) were dispersed in cytoplasm. The cytoplasmic dispersed Daxx mutants could be relocalized to nucleus by cotransfection with active SUMO, but not with inactive SUMO-delta, demonstrating the role of SUMO on regulating the cytoplasmonuclear transport of Daxx. However, inactive SUMO-delta could also be relocalized to nucleus during cotransfection with wild-type Daxx, suggesting that SUMO regulation of the cytoplasmonuclear transport of its target protein Daxx does not need covalent modification. This study shows that cytoplasmic SUMO has a biological role in enhancing the cytoplasmonuclear transport of its target protein Daxx and it may be done through the non-sumoylation interactions.
Center for Nanoscience, Institute of Biomedical Sciences, National Sun Yat-Sen University, Kaohsiung, Taiwan. achen@mail.nsysu.edu.tw
Angela
A
Chen
Ping-Yao
PY
Wang
Yu-Chih
YC
Yang
Yi-Hsin
YH
Huang
Jeng-Jung
JJ
Yeh
Yu-Huai
YH
Chou
Jiin-Tsuey
JT
Cheng
Yi-Ren
YR
Hong
Steven S-L
SS
Li
D021581:Active Transport, Cell Nucleus / Q000502:physiology; D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence / Q000235:genetics; D002467:Cell Nucleus / Q000378:metabolism*; D056970:Co-Repressor Proteins; D006367:HeLa Cells; D006801:Humans; D018832:Molecular Chaperones; D019913:Nuclear Localization Signals / Q000235:genetics / Q000378:metabolism*; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D011499:Protein Processing, Post-Translational / Q000502:physiology*; D025842:SUMO-1 Protein; D017384:Sequence Deletion / Q000235:genetics; D025841:Small Ubiquitin-Related Modifier Proteins / Q000235:genetics / Q000378:metabolism*
D048868:Adaptor Proteins, Signal Transducing; D056970:Co-Repressor Proteins; C106985:DAXX protein, human; D018832:Molecular Chaperones; D019913:Nuclear Localization Signals; D009687:Nuclear Proteins; D025842:SUMO-1 Protein; C495501:SUMO1 protein, human; D025841:Small Ubiquitin-Related Modifier Proteins