Retinoblastoma protein positively regulates terminal adipocyte differentiation through direct interaction with C/EBPs
Retinoblastoma protein positively regulates terminal adipocyte differentiation through direct interaction with C/EBPs
复制标题
DOI：
10.1101/gad.10.21.2794
复制
发表时间：
1996-11-01
影响因子：
10.5
通讯作者：
Lee, WH
中科院分区：
文献类型：
--
作者：
Chen, PL;Riley, DJ;Lee, WH
为了确定视网膜母细胞瘤蛋白（Rb）在细胞分化中发挥作用的机制，我们研究了野生型（RB（+/+））和空突变型（RB（-/-））小鼠胚胎肺芽的原代成纤维细胞。在培养中，RB（+/+）成纤维细胞自发或响应激素诱导分化为脂肪储存细胞;否则在相同条件下培养的同源RB（-/-）成纤维细胞不会分化。正常Rb的异位表达，而不是Rb与一个单一的点突变，使RB（-/-）成纤维细胞分化为脂肪细胞。Rb出现在鼠成纤维细胞中，以激活CCAAT/增强子结合蛋白（C/EBP），这是一个对脂肪细胞分化至关重要的转录因子家族。通过相互免疫共沉淀证明了Rb和C/EBP之间的物理相互作用，但仅发生在分化细胞中。野生型Rb还增强了体外C/EBP与同源DNA序列的结合以及细胞中C/EBP β响应启动子的反式激活。两者合计，这些观察结果建立了直接和积极的作用，Rb在终端分化。这种作用与Rb通过负调节其他转录因子如E2 F-1而阻止细胞周期进展到G（1）的功能形成对比。
To define a mechanism by which retinoblastoma protein (Rb) functions in cellular differentiation, we studied primary fibroblasts from the lung buds of wild-type (RB(+/+)) and null-mutant (RB(-/-)) mouse embryos. In culture, the RB(+/+) fibroblasts differentiated into fat-storing cells, either spontaneously or in response to hormonal induction; otherwise syngenic RB(-/-) fibroblasts cultured in identical conditions did not. Ectopic expression of normal Rb, but not Rb with a single point mutation, enabled RB(-/-) fibroblasts to differentiate into adipocytes. Rb appears in murine fibroblasts to activate CCAAT/enhancer-binding proteins (C/EBPs), a family of transcription factors crucial for adipocyte differentiation. Physical interaction between Rb and C/EBPs was demonstrated by reciprocal coimmunoprecipitation, but occurred only in differentiating cells. Wild-type Rb also enhanced the binding of C/EBP to cognate DNA sequences in vitro and the transactivation of a C/EBP beta-responsive promoter in cells. Taken together, these observations establish a direct and positive role for Rb in terminal differentiation. Such a role contrasts with the function of Rb in arresting cell cycle progression in G(1) by negative regulation of other transcription factors like E2F-1.