The carboxyl-terminal fragment of pro-HB-EGF reverses Bcl6-mediated gene repression
The carboxyl-terminal fragment of pro-HB-EGF reverses Bcl6-mediated gene repression
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DOI：
10.1074/jbc.m611036200
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发表时间：
2007-05-18
影响因子：
4.8
通讯作者：
Higashiyama, Shigeki
中科院分区：
文献类型：
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作者：
Kinugasa, Yumi;Hieda, Miki;Higashiyama, Shigeki
肝素结合表皮生长因子样生长因子（HB-EGF）是EGF家族的一员，是作为I型跨膜前体（pro-HB-EGF）合成的。前HB-EGF的外结构域脱落产生EGF受体氨基端可溶性配体（HB-EGF）和羧基端片段（HB-EGF- ctf），包括跨膜和细胞质结构域。我们之前的研究表明HB-EGF-CTF从质膜转运到细胞核，并作为信号分子发挥作用。免疫沉淀显示HB-EGF-CTF可以与哺乳动物细胞中的转录抑制因子Bcl6结合。谷胱甘肽s -转移酶下拉试验显示HB-EGF-CTF与Bcl6的锌指4-6有效相互作用。荧光素酶报告基因实验显示HB-EGF-CTF的核易位在Bcl6释放后逆转了细胞周期蛋白D2的转录抑制。此外，细胞周期蛋白D2水平升高，Bcl6与细胞周期蛋白D2启动子的相互作用降低，与内源性pro-HB-EGF水平的脱落平行。这些发现表明HB-EGF-CTF通过与转录抑制因子Bcl6的相互作用是基因表达的有效调节剂。
Heparin-binding epidermal growth factor-like growth factor (HB-EGF), a member of the EGF family, is synthesized as a type I transmembrane precursor (pro-HB-EGF). Ectodomain shedding of pro-HB-EGF yields an amino-terminal soluble ligand of EGF receptor (HB-EGF) and a carboxyl-terminal fragment (HB-EGF-CTF) consisting of the transmembrane and cytoplasmic domains. We previously showed that the HB-EGF-CTF translocates from the plasma membrane to the nucleus and plays a role as a signaling molecule. Immunoprecipitation showed that HB-EGF-CTF can associate with Bcl6, a transcriptional repressor in mammalian cells. A glutathione S-transferase pulldown assay revealed that HB-EGF-CTF interacted efficiently with zinc fingers 4-6 of Bcl6. A luciferase reporter assay showed that the nuclear translocation of HB-EGF-CTF following shedding reversed transcriptional repression of cyclin D2 by Bcl6. Additionally, the level of cyclin D2 protein increased and Bcl6 interaction with the cyclin D2 promoter decreased in parallel with the shedding of pro-HB-EGF at all endogenous levels. These findings suggest that HB-EGF-CTF is a potent regulator of gene expression via its interaction with the transcriptional repressor Bcl6.