Regulation of GATA-binding Protein 2 Levels via Ubiquitin-dependent Degradation by Fbw7 INVOLVEMENT OF CYCLIN B-CYCLIN-DEPENDENT KINASE 1-MEDIATED PHOSPHORYLATION OF THR

• Published in: The Journal of biological chemistry Vol. 290; no. 16; pp. 10368 - 10381
• Main Authors: Nakajima, Tomomi, Kitagawa, Kyoko, Ohhata, Tatsuya, Sakai, Satoshi, Uchida, Chiharu, Shibata, Kiyoshi, Minegishi, Naoko, Yumimoto, Kanae, Nakayama, Keiichi I., Masumoto, Kazuma, Katou, Fuminori, Niida, Hiroyuki, Kitagawa, Masatoshi
• Format: Journal Article
• Language: English
• Published: 11200 Rockville Pike, Suite 302, Rockville, MD 20852-3110, U.S.A American Society for Biochemistry and Molecular Biology 10.02.2015
• Subjects: Protein Synthesis and Degradation
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M114.613018

Background: SCF-Fbw7 participates in stability control of several Cdc4 phosphodegron-containing proteins phosphorylated by glycogen synthase kinase 3, an E3 ligase. Results: Ubiquitin-dependent degradation of GATA-binding protein 2 is promoted by Fbw7, is cyclin B-CDK1-mediated Thr 176 phosphorylation-dependent, and influences hematopoietic cell differentiation. Conclusion: GATA-binding protein 2 is a novel target for Fbw7. Significance: The molecular mechanism of post-transcriptional control of GATA-binding protein 2 is clarified. A GATA family transcription factor, GATA-binding protein 2 (GATA2), participates in cell growth and differentiation of various cells, such as hematopoietic stem cells. Although its expression level is controlled by transcriptional induction and proteolytic degradation, the responsible E3 ligase has not been identified. Here, we demonstrate that F-box/WD repeat-containing protein 7 (Fbw7/Fbxw7), a component of Skp1, Cullin 1, F-box-containing complex (SCF)-type E3 ligase, is an E3 ligase for GATA2. GATA2 contains a cell division control protein 4 (Cdc4) phosphodegron (CPD), a consensus motif for ubiquitylation by Fbw7, which includes Thr 176 . Ectopic expression of Fbw7 destabilized GATA2 and promoted its proteasomal degradation. Substitution of threonine 176 to alanine in GATA2 inhibited binding with Fbw7, and the ubiquitylation and degradation of GATA2 by Fbw7 was suppressed. The CPD kinase, which mediates the phosphorylation of Thr 176 , was cyclin B-cyclin-dependent kinase 1 (CDK1). Moreover, depletion of endogenous Fbw7 stabilized endogenous GATA2 in K562 cells. Conditional Fbw7 depletion in mice increased GATA2 levels in hematopoietic stem cells and myeloid progenitors at the early stage. Increased GATA2 levels in Fbw7-conditional knock-out mice were correlated with a decrease in a c-Kit high expressing population of myeloid progenitor cells. Our results suggest that Fbw7 is a bona fide E3 ubiquitin ligase for GATA2 in vivo .