Hefei National Laboratory for Physical Sciences at the Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui 230026, China.
Biochem J. 2013 Feb 15;450(1):85-94. doi: 10.1042/BJ20121382.
Human RBM25 (RNA-binding motif protein 25) is a novel splicing factor that contains a PWI domain, a newly identified RNA/DNA-binding domain, and regulates Bcl-x pre-mRNA alternative splicing. The flanking basic region has been suggested to serve as a co-operative partner of the PWI domain in the binding of nucleic acids, but the structure of this basic region is unknown. In the present paper, we report the crystal structure of the RBM25 PWI domain and its flanking basic region. The PWI domain is revealed to comprise a conserved four-helix bundle, and the flanking basic region forms two α-helices and associates with helix H4 of the PWI domain. These interactions promote directly the formation of an enlarged nucleic-acid-binding platform. Structure-guided mutagenesis reveals a positively charged nucleic-acid-binding surface in the RBM25 PWI domain that is entirely different from that in the SRm160 PWI domain. Furthermore, we show that the promotion of the pro-apoptotic Bcl-xS isoform expression by RBM25 is facilitated by the PWI domain in vivo. Thus the present study suggests that the PWI domain plays an important role in the regulation of Bcl-x pre-mRNA alternative splicing.
人类 RBM25（RNA 结合基序蛋白 25）是一种新型剪接因子，包含一个 PWI 结构域，这是一个新鉴定的 RNA/DNA 结合结构域，可调节 Bcl-x 前体 mRNA 的选择性剪接。侧翼碱性区被认为是 PWI 结构域结合核酸的协同伴侣，但该碱性区的结构尚不清楚。在本文中，我们报告了 RBM25 PWI 结构域及其侧翼碱性区的晶体结构。结果表明，PWI 结构域由一个保守的四螺旋束组成，侧翼碱性区形成两个α-螺旋，并与 PWI 结构域的 H4 螺旋结合。这些相互作用直接促进了一个扩大的核酸结合平台的形成。基于结构的突变分析揭示了 RBM25 PWI 结构域中的一个带正电荷的核酸结合表面，与 SRm160 PWI 结构域中的完全不同。此外，我们还表明，RBM25 在体内通过 PWI 结构域促进促凋亡 Bcl-xS 异构体的表达。因此，本研究表明 PWI 结构域在调节 Bcl-x 前体 mRNA 选择性剪接中发挥重要作用。
