Transcriptional regulation of the target genes of transforming growth factor-β and it's abnormalities in disease.

转化生长因子-β靶基因的转录调控及其在疾病中的异常。

基本信息

批准号：
14570208
负责人：
KATO Mitsuyasu
金额：
$ 2.62万
依托单位：
University of Tsukuba
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2002
资助国家：
日本
起止时间：
2002 至 2003
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-14570208/
关键词：
TGF-β Smad transcription c-myc WNT TCF-4 LEF-1 c-Ski TIE E2Fエレメント smad β-catemin TBE3エレメント

项目摘要

We have identified a TIE/E2F element that is critical for transcriptional regulation of c-myc in both serum-induced induction and TGF-β-induced suppression. Another element TBE3 that is activated by WNT signaling is also identified in the transcriptional regulatory region of c-myc. TGF-β-activated Smad3 binds a TIE/E2F element and dissociates p300 from E2F-4. On TBE3, TCF-4 releases β-catenin when binds Smad3. However, LEF-1 can bind both β-catenin and Smad3 at the same time. Therefore, transcriptional activity of c-myc activated by β-catenin is blocked by TGF-β in the presence of TCF-4 but it is resistant in the presence of LEE-1. These results suggested that enhanced, LEF-1 expression frequently observed in colon cancer might cancel TGF-β-induced repression of c-myc.Smad2D450E mutant was previously identified in colon caner. TGF-β signaling could not phosphorylate this mutant. We have shown that Smad2D450E can block phosphorylation of co-expressed wild-type Smad2 but not of Smad3, and that binding of Smad3 and Smad4 was not blocked by Smad2D450E either. However, Smad2D450E blocked the binding of Smad3 to it's target DNA and suppressed Smad3-responsive gene expression. Therefore, Smad2D450E is suggested to block Smad3 function either in the step of nuclear translocation or in the nucleus.We have examined the effects of c-Ski on the transcriptional repression of c-myc by TGF-β. c-Ski recovered transcriptional activity of c-myc suppressed by TGF-β. This function of c-Ski is not explained by known molecular function of c-Ski. We propose the novel role of c-Ski. c-Ski is suggested to compete the binding of an active Smad complex on their target DNA by extending the binding of an inactive Smad-c-Ski complex on the target DNA.

我们已经鉴定出一个 TIE/E2F 元件，该元件在血清诱导的诱导和 TGF-β 诱导的抑制中对 c-myc 的转录调节至关重要。在 c-myc 的转录调节区域中还鉴定了另一个由 WNT 信号传导激活的元件 TBE3。 c-myc 激活的 Smad3 结合 TIE/E2F 元件，并在 TBE3 上解离 p300，TCF-4 释放 β-连环蛋白。然而，LEF-1 可以同时结合 β-catenin 和 Smad3，因此，在 TCF-4 存在的情况下，β-catenin 激活的 c-myc 转录活性会被 TGF-β 阻断。这些结果表明，在结肠癌中经常观察到的增强的 LEF-1 表达可能会取消 TGF-β 诱导的 c-myc 抑制。Smad2D450E 突变体先前在我们已经证明，Smad2D450E 可以阻断共表达的野生型 Smad2 的磷酸化，但不能阻断 Smad3 的磷酸化，并且 Smad3 和 Smad4 的结合也不会被 Smad2D450E 阻断。 Smad2D450E 阻断 Smad3 与其靶 DNA 的结合，并抑制 Smad3 响应基因的表达。因此，Smad2D450E 被认为可以在核易位步骤或在细胞核内阻断 Smad3 功能。我们研究了 c-Ski 对恢复 c-myc 转录活性的 TGF-β 转录抑制的影响。 c-myc 被 TGF-β 抑制。c-Ski 的这种功能不能用 c-Ski 的已知分子功能来解释。我们建议 c-Ski 的新作用是竞争。通过延长非活性 Smad-c-Ski 复合物在目标 DNA 上的结合，使活性 Smad 复合物与其目标 DNA 结合。