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SCF Fbxw7 ubiquitylates KLF7 for degradation in a manner dependent on GSK‐3‐mediated phosphorylation
Author(s) -
Sugiyama Shigeaki,
Yumimoto Kanae,
Inoue Ippei,
Nakayama Keiichi I.
Publication year - 2019
Publication title -
genes to cells
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.912
H-Index - 115
eISSN - 1365-2443
pISSN - 1356-9597
DOI - 10.1111/gtc.12680
Subject(s) - biology , cell division control protein 4 , ubiquitin ligase , ubiquitin , f box protein , microbiology and biotechnology , gsk 3 , mutation , phosphorylation , genetics , gene
The biological relation between ubiquitin ligases and their substrates has been largely unclear. We previously developed a method—differential proteomics‐based identification of ubiquitylation substrates (DiPIUS)—for the comprehensive identification of substrates for a given ubiquitin ligase. We have now applied DiPIUS to the F‐box protein Fbxw7 in three cell lines (mHepa, Neuro2A and C2C12) and thereby identified Krüppel‐like factor 7 (KLF7) as a candidate substrate of the SCF Fbxw7 ubiquitin ligase complex. KLF7 was shown to interact with Fbxw7 and to undergo Fbxw7‐mediated polyubiquitylation. The stability of KLF7 was increased by depletion of Fbxw7, mutation of a putative Cdc4 phosphodegron (CPD) of KLF7 or exposure to inhibitors of glycogen synthase kinase‐3 (GSK‐3). Over‐expression of Fbxw7 in Neuro2A cells down‐regulated expression of the p21 Cip1 gene, which is a transcriptional target of KLF7 in neuronal differentiation and maintenance. Despite the presence of an almost identical CPD sequence in KLF6, the closest paralog of KLF7, mutation of this sequence affected neither the interaction of KLF6 with Fbxw7 nor its half‐life. Our results suggest that KLF7, but not KLF6, is a bona fide substrate of SCF Fbxw7 , and that control of KLF7 abundance by SCF Fbxw7 might contribute to the regulation of neuronal differentiation and maintenance.