Nuclear oncoprotein prothymosin alpha is a partner of Keap1: implications for expression of oxidative stress-protecting genes.
Animal cells counteract oxidative stress and electrophilic attack through coordinated expression of a set of detoxifying and antioxidant enzyme genes mediated by transcription factor Nrf2. In unstressed cells, Nrf2 appears to be sequestered in the cytoplasm via association with an inhibitor protein, Keap1. Here, by using the yeast two-hybrid screen, human Keap1 has been identified as a partner of the nuclear protein prothymosin alpha. The in vivo and in vitro data indicated that the prothymosin alpha-Keap1 interaction is direct, highly specific, and functionally relevant. Furthermore, we showed that Keap1 is a nuclear-cytoplasmic shuttling protein equipped with a nuclear export signal that is important for its inhibitory action. Prothymosin alpha was able to liberate Nrf2 from the Nrf2-Keap1 inhibitory complex in vitro through competition with Nrf2 for binding to the same domain of Keap1. In vivo, the level of Nrf2-dependent transcription was correlated with the intracellular level of prothymosin alpha by using prothymosin alpha overproduction and mRNA interference approaches. Our data attribute to prothymosin alpha the role of intranuclear dissociator of the Nrf2-Keap1 complex, thus revealing a novel function for prothymosin alpha and adding a new dimension to the molecular mechanisms underlying expression of oxidative stress-protecting genes.
Karapetian
Ruben N
RN
Belozersky Institute of Physico-Chemical Biology, Moscow State University, Moscow 119992, Russia.
Evstafieva
Alexandra G
AG
Abaeva
Irina S
IS
Chichkova
Nina V
NV
Filonov
Grigoriy S
GS
Rubtsov
Yuri P
YP
Sukhacheva
Elena A
EA
Melnikov
Sergey V
SV
Schneider
Ulrich
U
Wanker
Erich E
EE
Vartapetian
Andrey B
AB
D021581:Active Transport, Cell Nucleus / Q000235:genetics / Q000502:physiology; D004268:DNA-Binding Proteins / Q000378:metabolism*; D015972:Gene Expression Regulation, Neoplastic / Q000235:genetics / Q000502:physiology; D006367:HeLa Cells; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D000072019:Kelch-Like ECH-Associated Protein 1; D051267:NF-E2-Related Factor 2; D018384:Oxidative Stress / Q000235:genetics* / Q000502:physiology; D011485:Protein Binding; D011498:Protein Precursors / Q000378:metabolism*; D011506:Proteins / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000378:metabolism; D013947:Thymosin / Q000031:analogs & derivatives* / Q000378:metabolism*; D015534:Trans-Activators / Q000378:metabolism*; D015533:Transcriptional Activation / Q000235:genetics* / Q000502:physiology; D014407:Tumor Cells, Cultured; D020798:Two-Hybrid System Techniques
D004268:DNA-Binding Proteins; D047908:Intracellular Signaling Peptides and Proteins; C431364:KEAP1 protein, human; D000072019:Kelch-Like ECH-Associated Protein 1; D051267:NF-E2-Related Factor 2; C495635:NFE2L2 protein, human; D011498:Protein Precursors; D011506:Proteins; D034741:RNA, Small Interfering; D015534:Trans-Activators; C040782:prothymosin alpha; D013947:Thymosin