NF-κB1 inhibits c-Myc protein degradation through suppression of FBW7 expression
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Haishan Huang1,2, Li Ma2, Jingxia Li2, Yonghui Yu2, Dongyun Zhang2, Jinlong Wei1,2, Honglei Jin1,2, Derek Xu2,3, Jimin Gao1 and Chuanshu Huang2
1 Zhejiang Provincial Key Laboratory for Technology & Application of Model Organisms, School of Life Sciences, Wenzhou Medical University, Wenzhou, Zhejiang, China
2 Nelson Institute of Environmental Medicine, New York University School of Medicine, Tuxedo, NY, USA
3 Jericho High School, Jericho, NY
Chuanshu Huang, email:
Jimin Gao, email:
Keywords: NF-κB p50, arsenite, c-Myc, protein degradation, FBW7
Received: November 29, 2013 Accepted: January 15, 2014 Published: January 15, 2014
NF-κB is a well-known transcription factor in regulation of multiple gene transcription and biological processes, and most of them are relied on its transcriptional activity of the p65/RelA subunit, while biological function of another ubiquitously expressed subunit NF-κB1 (p50) remains largely unknown due to lack transcriptional activation domain. Here we discovered a novel biological function of p50 as a regulator of oncogenic c-Myc protein degradation upon arsenite treatment in a NF-κB transcriptional-independent mechanism. Our results found that p50 was crucial for c-Myc protein induction following arsenite treatment by using specific knockdown and deletion of p50 in its normal expressed cells as well as reconstituting expression of p50 in its deficient cells. Subsequently we showed that p50 upregulated c-Myc protein expression mainly through inhibiting its degradation. We also identified that p50 exhibited this novel property by suppression of FBW7 expression. FBW7 was profoundly upregulated in p50-defecient cells in comparison to that in p50 intact cells, whereas knockdown of FBW7 in p50-/- cells restored arsenite-induced c-Myc protein accumulation, assuring that FBW7 up-regulation was responsible for defect of c-Myc protein expression in p50-/- cells. In addition, we discovered that p50 suppressed fbw7 gene transcription via inhibiting transcription factor E2F1 transactivation. Collectively, our studies demonstrated a novel function of p50 as a regulator of c-Myc protein degradation, contributing to our notion that p50-regulated protein expression through multiple levels at protein translation and degradation, further providing a significant insight into the understanding of biomedical significance of p50 protein.
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