Nelson R W, Gumbiner B M
Cellular Biochemistry and Biophysics Program, Memorial Sloan-Kettering Cancer Center, New York, New York 10021, USA.
Ann N Y Acad Sci. 1998 Oct 23;857:86-98. doi: 10.1111/j.1749-6632.1998.tb10109.x.
Beta-catenin is shown to directly induce the expression of siamois (a homeobox-containing gene involved in axial patterning) in a cell-autonomous, protein synthesis independent manner. Siamois can thus be considered a direct target of beta-catenin signaling in Xenopus. Expression of a portion of the armadillo repeat region of beta-catenin via a membrane-tethered fusion protein is shown to give similar levels of siamois induction and axis duplication as a free, untethered form. Reduction of endogenous free beta-catenin levels by overexpression of C-cadherin leads to complete inhibition of signaling by the membrane-tethered repeat region. Since the membrane-tethered repeat region is unlikely to be bound up by C-cadherin, these results show that the membrane-tethered beta-catenin relies on endogenous beta-catenin for signaling. We propose that the membrane-tethered construct acts by titrating a cytoplasmic inhibitor of beta-catenin signaling.
β-连环蛋白被证明能以细胞自主、不依赖蛋白质合成的方式直接诱导西阿莫斯（一种参与轴向模式形成的含同源框基因）的表达。因此，西阿莫斯可被视为非洲爪蟾中β-连环蛋白信号传导的直接靶点。通过膜 tethered 融合蛋白表达β-连环蛋白的一部分犰狳重复区域，显示出与游离的、未 tethered 形式相似水平的西阿莫斯诱导和轴重复。通过过表达 C-钙黏着蛋白降低内源性游离β-连环蛋白水平，导致膜 tethered 重复区域的信号传导完全被抑制。由于膜 tethered 重复区域不太可能被 C-钙黏着蛋白结合，这些结果表明膜 tetheredβ-连环蛋白信号传导依赖于内源性β-连环蛋白。我们提出，膜 tethered 构建体通过滴定β-连环蛋白信号传导的细胞质抑制剂起作用。
