Mastermind mediates chromatin-specific transcription and turnover of the Notch enhancer complex
Mastermind mediates chromatin-specific transcription and turnover of the Notch enhancer complex
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DOI：
10.1101/gad.991602
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发表时间：
2002-06-01
影响因子：
10.5
通讯作者：
Jones, KA
中科院分区：
文献类型：
--
作者：
Fryer, CJ;Lamar, E;Jones, KA
通过Notch途径的信号传导激活Notch胞内结构域（ICD）的蛋白水解释放，所述ICD是CSL增强子结合蛋白的专用转录共激活因子。在这里，我们表明，染色质依赖性的反式激活的重组Notch ICD-CBF 1增强子复合物在体外需要一个额外的辅激活剂，Mastermind（MAM）。MAM为哺乳动物细胞和非洲爪蟾胚胎中的Notch信号传导提供了两个必需的激活结构域。我们发现，中央MAM激活结构域（TAD 1）招募CBP/p300，以促进Notch增强子处的核小体乙酰化，并激活体外转录。我们还发现，MAM表达诱导内源性CBP/p300蛋白的磷酸化和重新定位到体内核灶。此外，我们发现，与MAM和CBF 1的共表达强烈增强了体内Notch ICD的磷酸化和蛋白水解周转。ICD和p300的增强磷酸化需要MAM（TAD 2）的富含谷氨酰胺的区域，其对于体内Notch转录是必需的。因此，MAM可以作为计时器来将转录激活与染色质上的Notch增强子复合物的分解偶联。
Signaling through the Notch pathway activates the proteolytic release of the Notch intracellular domain (ICD), a dedicated transcriptional coactivator of CSL enhancer-binding proteins. Here we show that chromatin-dependent transactivation by the recombinant Notch ICD-CBF1 enhancer complex in vitro requires an additional coactivator, Mastermind (MAM). MAM provides two activation domains necessary for Notch signaling in mammalian cells and in Xenopus embryos. We show that the central MAM activation domain (TAD1) recruits CBP/p300 to promote nucleosome acetylation at Notch enhancers and activate transcription in vitro. We also find that MAM expression induces phosphorylation and relocalization of endogenous CBP/p300 proteins to nuclear foci in vivo. Moreover, we show that coexpression with MAM and CBF1 strongly enhances phosphorylation and proteolytic turnover of the Notch ICD in vivo. Enhanced phosphorylation of the ICD and p300 requires a glutamine-rich region of MAM (TAD2) that is essential for Notch transcription in vivo. Thus MAM may function as a timer to couple transcription activation with disassembly of the Notch enhancer complex on chromatin.