Department of Pathology and Immunology, Baylor College of Medicine, Houston, TX 77030, USA.
Nucleic Acids Res. 2011 Apr;39(7):2769-80. doi: 10.1093/nar/gkq1155. Epub 2010 Nov 24.
Muscleblind-like 1 (MBNL1) is a splicing regulator that controls developmentally regulated alternative splicing of a large number of exons including exon 11 of the Insulin Receptor (IR) gene and exon 5 of the cardiac Troponin T (cTNT) gene. There are three paralogs of MBNL in humans, all of which promote IR exon 11 inclusion and cTNT exon 5 skipping. Here, we identify a cluster of three binding sequences located downstream of IR exon 11 that constitute the MBNL1 response element and a weaker response element in the upstream intron. In addition, we used sequential deletions to define the functional domains of MBNL1 and MBNL3. We demonstrate that the regions required for splicing regulation are separate from the two pairs of zinc-finger RNA-binding domains. MBNL1 and MBNL3 contain core regulatory regions for both activation and repression located within an 80-amino-acid segment located downstream of the N-terminal zinc-finger pair. Deletions of these regions abolished regulation without preventing RNA binding. These domains have common features with the CUG-BP and ETR3-like Factor (CELF) family of splicing regulators. These results have identified protein domains required for splicing repression and activation and provide insight into the mechanism of splicing regulation by MBNL proteins.
肌肉萎缩症相关蛋白 1（MBNL1）是一种剪接调控因子，可调控包括胰岛素受体（IR）基因外显子 11 和心肌肌钙蛋白 T（cTNT）基因外显子 5 等大量外显子的发育调控性可变剪接。人类有三个 MBNL 的同源物，它们都促进 IR 外显子 11 的包含和 cTNT 外显子 5 的跳过。在这里，我们鉴定了位于 IR 外显子 11 下游的三个结合序列簇，它们构成了 MBNL1 反应元件和上游内含子中的较弱反应元件。此外，我们使用连续缺失来定义 MBNL1 和 MBNL3 的功能域。我们证明，剪接调节所需的区域与两个锌指 RNA 结合结构域分开。MBNL1 和 MBNL3 包含位于 N 端锌指对下游的 80 个氨基酸片段内的激活和抑制的核心调节区域。这些区域的缺失消除了调节作用，而不阻止 RNA 结合。这些结构域与 CUG-BP 和 ETR3 样因子（CELF）家族的剪接调节剂具有共同的特征。这些结果鉴定了剪接抑制和激活所需的蛋白结构域，并为 MBNL 蛋白的剪接调节机制提供了深入的了解。
