Maeder Corina, Kutach Alan K, Guthrie Christine
Department of Biochemistry and Biophysics, University of California, San Francisco, 600 16th Street, California 94143, USA.
Nat Struct Mol Biol. 2009 Jan;16(1):42-8. doi: 10.1038/nsmb.1535. Epub 2008 Dec 21.
The spliceosome is a highly dynamic machine requiring multiple RNA-dependent ATPases of the DExD/H-box family. A fundamental unanswered question is how their activities are regulated. Brr2 function is necessary for unwinding the U4/U6 duplex, a step essential for catalytic activation of the spliceosome. Here we show that Brr2-dependent dissociation of U4/U6 snRNAs in vitro is activated by a fragment from the C terminus of the U5 snRNP protein Prp8. In contrast to its helicase-stimulating activity, this fragment inhibits Brr2 U4/U6-dependent ATPase activity. Notably, U4/U6 unwinding activity is not stimulated by fragments carrying alleles of prp8 that in humans confers an autosomal dominant form of retinitis pigmentosa. Because Brr2 activity must be restricted to prevent premature catalytic activation, our results have important implications for fidelity maintenance in the spliceosome.
剪接体是一种高度动态的机器，需要DExD/H盒家族的多种RNA依赖性ATP酶。一个基本的未解决问题是它们的活性如何被调节。Brr2的功能对于解开U4/U6双链是必要的，这是剪接体催化激活所必需的一步。在这里，我们表明，U5 snRNP蛋白Prp8 C末端的一个片段在体外激活了Brr2依赖的U4/U6 snRNA解离。与其解旋酶刺激活性相反，该片段抑制Brr2 U4/U6依赖的ATP酶活性。值得注意的是，携带prp8等位基因的片段不会刺激U4/U6解旋活性，而在人类中，这些等位基因会导致常染色体显性形式的视网膜色素变性。由于必须限制Brr2的活性以防止过早的催化激活，我们的结果对剪接体中保真度的维持具有重要意义。
