Liu Li, Query Charles C, Konarska Maria M
The Rockefeller University, New York, New York 10021, USA.
Nat Struct Mol Biol. 2007 Jun;14(6):519-26. doi: 10.1038/nsmb1240. Epub 2007 May 7.
The spliceosome is thought to undergo a conformational change between the two catalytic steps of precursor messenger RNA splicing, although the specific events in this transition are poorly understood. We previously proposed a two-state model of splicing in which the conformations required for the first and second steps are in competition. Here, we identify and characterize a class of prp8 mutants that suppress first-step splicing defects and oppose the action of the previously described prp8 suppressors of second-step defects; these opposing effects parallel those of ribosomal 'ram' and 'restrictive' mutants, which alter fidelity of transfer RNA decoding. On the basis of genetic interactions, we propose that prp8-mediated substrate repositioning during the transition occurs between catalytic-center opening and closure mediated by the U6 small nuclear RNA and the DExH/D ATPase gene prp16. Modulation of these events alters splice-site selection and splicing fidelity.
剪接体被认为在前体信使核糖核酸剪接的两个催化步骤之间会发生构象变化，尽管这种转变中的具体事件还知之甚少。我们之前提出了一种剪接的双态模型，其中第一步和第二步所需的构象相互竞争。在这里，我们鉴定并表征了一类prp8突变体，它们能抑制第一步剪接缺陷，并对抗先前描述的第二步缺陷的prp8抑制子的作用；这些相反的效应类似于核糖体“ram”和“限制性”突变体的效应，后者会改变转运核糖核酸解码的保真度。基于遗传相互作用，我们提出在转变过程中由prp8介导的底物重新定位发生在由U6小核RNA和DExH/D ATP酶基因prp16介导的催化中心开放和关闭之间。对这些事件的调节会改变剪接位点选择和剪接保真度。
