酵母Prp3蛋白是U4/U6 snRNP和U4/U6.U5三snRNP完整性所必需的一种U4/U6 snRNP蛋白。
The yeast Prp3 protein is a U4/U6 snRNP protein necessary for integrity of the U4/U6 snRNP and the U4/U6.U5 tri-snRNP.
作者信息
Anthony J G, Weidenhammer E M, Woolford J L
机构信息
Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA.
出版信息
RNA. 1997 Oct;3(10):1143-52.
Previously, yeast prp3 mutants were found to be blocked prior to the first catalytic step of pre-mRNA splicing. No splicing intermediates or products are formed from pre-mRNA in heat-inactivated prp3 mutants or prp3 mutant extracts. Here we show that Prp3p is a component of the U4/U6 snRNP and is also present in the U4/U6.U5 tri-snRNP. Heat inactivation of prp3 extracts results in depletion of free U6 snRNPs and U4/U6.U5 tri-snRNPs, but not U4/U6 snRNPs or U5 snRNPs. Free U4 snRNP, normally not present in wild-type extracts, accumulates under these conditions. Assays of in vivo levels of snRNAs in a prp3 mutant revealed that amounts of free U6 snRNA decreased, free U4 snRNA increased, and U4/U6 hybrids decreased slightly. These results suggest that Prp3p is required for formation of stable U4/U6 snRNPs and for assembly of the U4/U6.U5 tri-snRNP from its component snRNPs. Upon inactivation of Prp3p, spliceosomes cannot assemble from prespliceosomes due to the absence of intact U4/U6.U5 tri-snRNPs. Prp3p is homologous to a human protein that is a component of U4/U6 snRNPs, exemplifying the conservation of splicing factors between yeast and metazoans.
此前发现，酵母prp3突变体在mRNA前体剪接的首个催化步骤之前就被阻断。在热失活的prp3突变体或prp3突变体提取物中，mRNA前体不会形成剪接中间体或产物。我们在此表明，Prp3p是U4/U6核内小核糖核蛋白颗粒（snRNP）的一个组分，并且也存在于U4/U6·U5三snRNP中。prp3提取物的热失活导致游离U6 snRNP和U4/U6·U5三snRNP耗竭，但不会导致U4/U6 snRNP或U5 snRNP耗竭。游离U4 snRNP（通常不存在于野生型提取物中）在这些条件下会积累。对prp3突变体中snRNA的体内水平进行的检测显示，游离U6 snRNA的量减少，游离U4 snRNA的量增加，并且U4/U6杂交体略有减少。这些结果表明，Prp3p对于稳定的U4/U6 snRNP的形成以及U4/U6·U5三snRNP由其组分snRNP组装而成是必需的。Prp3p失活后，由于缺乏完整的U4/U6·U5三snRNP，剪接体无法从前体剪接体组装而成。Prp3p与一种人类蛋白同源，该人类蛋白是U4/U6 snRNP的一个组分，这例证了酵母和后生动物之间剪接因子的保守性。
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