The PTB interacting protein raver1 regulates alpha-tropomyosin alternative splicing.
The PTB interacting protein raver1 regulates alpha-tropomyosin alternative splicing.
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发表时间：
2003
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通讯作者：
N. Gromak;Alexis P Rideau;J. Southby;A. Scadden;C. Gooding;S. Hüttelmaier;R. Singer;Christopher W. J. Smith
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作者：
N. Gromak;Alexis P Rideau;J. Southby;A. Scadden;C. Gooding;S. Hüttelmaier;R. Singer;Christopher W. J. Smith
α-原肌球蛋白(TM)相互排斥的外显子2和3的调控转换涉及到对平滑肌细胞中外显子3的抑制。多嘧啶结合蛋白(PTB)是调节TM剪接所必需的，但不是充分的。通过与细胞骨架蛋白肌动蛋白和纽蛋白的相互作用，在双杂交筛选中鉴定了Rver1，并发现它也与PTB相互作用。与这些相互作用相一致，raver1可以定位在细胞核或细胞质中。在这里，我们发现raver1能够通过增强PTB介导的对外显子3的抑制来促进TM的平滑肌特异性选择性剪接。这种活性依赖于特征的PTB结合调节元件以及与PTB相互作用所必需的raver1区域。异源募集raver1或其C末端导致了非常高水平的外显子3跳过，绕过了通常需要外显子3下游的PTB结合位点。这表明了PTB介导的剪接抑制的一种新机制，包括募集raver1作为一个有效的剪接辅助抑制因子。
Regulated switching of the mutually exclusive exons 2 and 3 of alpha-tropomyosin (TM) involves repression of exon 3 in smooth muscle cells. Polypyrimidine tract-binding protein (PTB) is necessary but not sufficient for regulation of TM splicing. Raver1 was identified in two-hybrid screens by its interactions with the cytoskeletal proteins actinin and vinculin, and was also found to interact with PTB. Consistent with these interactions raver1 can be localized in either the nucleus or cytoplasm. Here we show that raver1 is able to promote the smooth muscle-specific alternative splicing of TM by enhancing PTB-mediated repression of exon 3. This activity of raver1 is dependent upon characterized PTB-binding regulatory elements and upon a region of raver1 necessary for interaction with PTB. Heterologous recruitment of raver1, or just its C-terminus, induced very high levels of exon 3 skipping, bypassing the usual need for PTB binding sites downstream of exon 3. This suggests a novel mechanism for PTB-mediated splicing repression involving recruitment of raver1 as a potent splicing co-repressor.