Fbw7 promotes ubiquitin-dependent degradation of c-Myb: involvement of GSK3-mediated phosphorylation of Thr-572 in mouse c-Myb
Fbw7 promotes ubiquitin-dependent degradation of c-Myb: involvement of GSK3-mediated phosphorylation of Thr-572 in mouse c-Myb
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DOI：
10.1038/onc.2009.111
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发表时间：
2009-06-01
期刊：
影响因子：
8
通讯作者：
Kitagawa, M.
中科院分区：
文献类型：
--
作者：
Kitagawa, K.;Hiramatsu, Y.;Kitagawa, M.
癌蛋白 c-Myb 的表达在造血和血液恶性肿瘤过程中出现振荡。其数量不仅通过转录控制进行调节，还通过泛素-蛋白酶体途径进行调节，并伴有磷酸化，尽管其机制尚不清楚。在本报告中，我们试图鉴定一种 E3 泛素连接酶，其靶向 c-Myb 进行泛素依赖性降解。我们发现 F-box 蛋白 Fbw7 与 c-Myb 相互作用，c-Myb 在多种癌症中发生突变。 Fbw7 促进完整细胞中 c-Myb 的泛素化和降解。此外，通过RNA干扰消除Fbw7会延迟周转，同时增加髓性白血病细胞中c-Myb的丰度，并抑制γ-珠蛋白的转录水平，γ-珠蛋白受到c-Myb的转录抑制。此外，我们分析了 c-Myb 泛素化和降解所需的位点。我们发现 Thr-572 对于使用定点诱变的小鼠 c-Myb 中 Fbw7 介导的泛素化至关重要。 Fbw7 识别 Thr-572 的磷酸化，这是由糖原合成酶激酶 3 (GSK3) 介导的。因此，通过将 Thr-572 替换为 Ala，c-Myb 蛋白显着稳定。这些观察结果表明 SCFFbw7 泛素连接酶调节 c-Myb 蛋白的磷酸化依赖性降解。癌基因 (2009) 28, 2393-2405; doi：10.1038/onc.2009.111； 2009 年 5 月 4 日在线发布
Expression of oncoprotein c-Myb oscillates during hematopoiesis and hematological malignancies. Its quantity is not only regulated through transcriptional control but also through the ubiquitin-proteasome pathway, accompanied by phosphorylation, although the mechanisms are poorly understood. In this report, we tried to identify an E3 ubiquitin ligase, which targets c-Myb for ubiquitin-dependent degradation. We found that an F-box protein, Fbw7, interacted with c-Myb, which is mutated in numerous cancers. Fbw7 facilitated ubiquitylation and degradation of c-Myb in intact cells. Moreover, depletion of Fbw7 by RNA interference delayed turnover and increased the abundance of c-Myb in myeloid leukemia cells concomitantly, and suppressed the transcriptional level of gamma-globin, which receives transcriptional repression from c-Myb. In addition, we analysed sites required for both ubiquitylation and degradation of c-Myb. We found that Thr-572 is critical for Fbw7-mediated ubiquitylation in mouse c-Myb using site-directed mutagenesis. Fbw7 recognized the phosphorylation of Thr-572, which was mediated by glycogen synthase kinase 3 (GSK3). In consequence, the c-Myb protein was markedly stabilized by the substitution of Thr-572 to Ala. These observations suggest that SCFFbw7 ubiquitin ligase regulates phosphorylation-dependent degradation of c-Myb protein. Oncogene (2009) 28, 2393-2405; doi:10.1038/onc.2009.111; published online 4 May 2009