Wwp2, an E3 ubiquitin ligase that targets transcription factor Oct-4 for ubiquitination.
The POU transcription factor Oct-4 is a master regulator affecting the fate of pluripotent embryonic stem cells. However, the precise mechanisms by which the activation and expression of Oct-4 are regulated still remain to be elucidated. We describe here a novel murine ubiquitin ligase, Wwp2, that specifically interacts with Oct-4 and promotes its ubiquitination both in vivo and in vitro. Remarkably, the expression of a catalytically inactive point mutant of Wwp2 abolishes Oct-4 ubiquitination. Moreover, Wwp2 promotes Oct-4 degradation in the presence of overexpressed ubiquitin. The degradation is blocked by treatment with proteasome inhibitor. Fusion of a single ubiquitin to Oct-4 inactivates its transcriptional activity in a heterologous Oct-4-driven reporter system. Furthermore, overexpression of Wwp2 in embryonic stem cells significantly reduces the Oct-4-transcriptional activities. Collectively, we demonstrate for the first time that Oct-4 can be post-translationally modified by ubiquitination and that this modification dramatically suppresses its transcriptional activity. These results reveal that the functional status of Oct-4, in addition to its expression level, dictates its transcriptional activity, and the results open up a new avenue to understand how Oct-4 defines the fate of embryonic stem cells.
Xu
Hui Ming
HM
Developmental Biology Department, Health Science Center, Shanghai Second Medical University and Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, 411 He Fei Road, Shanghai 200025, China.
Liao
Bing
B
Zhang
Qian Jun
QJ
Wang
Bei Bei
BB
Li
Hui
H
Zhong
Xiao Min
XM
Sheng
Hui Zhen
HZ
Zhao
Ying Xin
YX
Zhao
Ying Ming
YM
Jin
Ying
Y
D000818:Animals; D002454:Cell Differentiation; D004268:DNA-Binding Proteins / Q000378:metabolism*; D051379:Mice; D050814:Octamer Transcription Factor-3; D011485:Protein Binding; D015398:Signal Transduction; D013234:Stem Cells / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism*; D014452:Ubiquitins / Q000378:metabolism
D004268:DNA-Binding Proteins; D050814:Octamer Transcription Factor-3; C494174:Pou5f1 protein, mouse; D014157:Transcription Factors; D014452:Ubiquitins; C487995:Wwp2 protein, mouse; D044767:Ubiquitin-Protein Ligases