MITF and cell proliferation: the role of alternative splice forms
MITF and cell proliferation: the role of alternative splice forms
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DOI：
10.1111/j.1600-0749.2005.00249.x
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发表时间：
2005-10-01
期刊：
影响因子：
--
通讯作者：
Arnheiter, H
中科院分区：
文献类型：
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作者：
Bismuth, K;Maric, D;Arnheiter, H
最近的研究表明，黑素细胞转录因子MITF不仅激活分化基因，还激活参与细胞周期调控的基因，表明它在细胞增殖和分化之间提供了联系。然而，MITF有多种剪接异构体，具有潜在的不同生物学活性。特别是，有两种异构体，(-)和(+)MITF，它们位于DNA结合碱性结构域上游的六个残基上不同，它们与靶DNA结合的效率略有不同。通过体外BrdU掺入实验和瞬时转染细胞的FACS分析，我们发现(+)MITF对DNA合成有很强的抑制作用，而(-)MITF没有或只有轻微的抑制作用。(+)MITF的强大抑制活性不受许多调节MITF转录活性的突变的影响，并且不依赖于蛋白质的羧基末端，而依赖于其氨基末端。对分子的进一步剖析指出了氨基末端丝氨酸的重要性，丝氨酸-73在两种异构体中都被磷酸化到了类似的程度。结果表明，一个或几个氨基末端结构域与选择性剪接的六肽协同作用，以一种不依赖于直接E盒结合的方式使MITF具有抗增殖作用。
Recent studies show that the melanocyte transcription factor MITF not only activates differentiation genes but also genes involved in the regulation of the cell cycle, suggesting that it provides a link between cell proliferation and differentiation. MITF, however, comes in a variety of splice isoforms with potentially distinct biological activities. In particular, there are two isoforms, (-) and (+) MITF, that differ in six residues located upstream of the DNA binding basic domain and show slight differences in the efficiency with which they bind to target DNA. Using in vitro BrdU incorporation assays and FACS analysis in transiently transfected cells, we show that (+) MITF has a strong inhibitory effect on DNA synthesis while (-) MITF has none or only a mild one. The strong inhibitory activity of (+) MITF is not influenced by a number of mutations that modulate MITF's transcriptional activities and is independent of the protein's carboxyl terminus but dependent on its aminoterminus. A further dissection of the molecule points to the importance of an aminoterminal serine, serine-73, which in both isoforms is phosphorylated to comparable degrees. The results suggest that one or several aminoterminal domains cooperate with the alternatively spliced hexapeptide to render MITF anti-proliferative in a way that does not depend on direct E box binding.