Suzuki Hitoshi, Jin Yui, Otani Hifumi, Yasuda Kunio, Inoue Kunio
Graduate School of Biological Sciences, Nara Institute of Science and Technology, Ikoma 630-0101, Japan.
Genes Cells. 2002 Feb;7(2):133-41. doi: 10.1046/j.1356-9597.2001.00506.x.
The Bruno-like or CELF proteins, such as mammalian CUGBP1 and Etr-3, Xenopus EDEN-BP, and Drosophila Bruno (Bru), are regulators of gene expression at the post-transcriptional level, and contain three RNA-recognition motifs (RRMs). It has been shown that mammalian CUGBP1 and Etr-3 regulate alternative splicing of cardiac troponin T pre-mRNA via binding to CUG-triplet repeats.
Using in vitro selection and UV-crosslinking experiments, we found that zebrafish Bruno-like proteins bound to repeat elements of uridine and purine (termed UREs). It is known that non-muscle (NM) and smooth muscle (SM) exons of the rat alpha-actinin gene are used in a mutually exclusive manner. Transfection experiments in mammalian cells showed that zebrafish Brul and Etr-3 induced the muscle-specific splicing of rat alpha-actinin pre-mRNA via binding to the URE at the branch point upstream of the NM exon. In contrast, zebrafish Etr-1 promoted skipping of both the NM and SM exons in a manner which was not dependent on URE-binding.
Our results showed that Bruno-like proteins bind to UREs and regulate the alternative splicing of alpha-actinin pre-mRNA. Members of the Bruno family play multiple roles in splicing regulation.
类布鲁诺蛋白或CELF蛋白，如哺乳动物的CUGBP1和Etr-3、非洲爪蟾的EDEN-BP以及果蝇的布鲁诺（Bru），是转录后水平基因表达的调控因子，且包含三个RNA识别基序（RRMs）。研究表明，哺乳动物的CUGBP1和Etr-3通过与CUG三联体重复序列结合来调节心肌肌钙蛋白T前体mRNA的可变剪接。
通过体外筛选和紫外线交联实验，我们发现斑马鱼类布鲁诺蛋白与尿苷和嘌呤的重复元件（称为UREs）结合。已知大鼠α-辅肌动蛋白基因的非肌肉（NM）外显子和平滑肌（SM）外显子以互斥方式使用。在哺乳动物细胞中进行的转染实验表明，斑马鱼Brul和Etr-3通过与NM外显子上游分支点处的URE结合，诱导大鼠α-辅肌动蛋白前体mRNA的肌肉特异性剪接。相反，斑马鱼Etr-1以一种不依赖于URE结合的方式促进NM和SM外显子的跳跃。
我们的结果表明，类布鲁诺蛋白与UREs结合并调节α-辅肌动蛋白前体mRNA的可变剪接。布鲁诺家族成员在剪接调控中发挥多种作用。
