Seshadri V, Vaidya V C, Vijayraghavan U
Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore, India.
Genetics. 1996 May;143(1):45-55. doi: 10.1093/genetics/143.1.45.
The PRP17 gene product is required for the second step of pre-mRNA splicing reactions. The C-terminal half of this protein bears four repeat units with homology to the beta transducin repeat. Missense mutations in three temperature-sensitive prp17 mutants map to a region in the N-terminal half of the protein. We have generated, in vitro, 11 missense alleles at the beta transducin repeat units and find that only one affects function in vivo. A phenotypically silent missense allele at the fourth repeat unit enhances the slow-growing phenotype conferred by an allele at the third repeat, suggesting an interaction between these domains. Although many missense mutations in highly conserved amino acids lack phenotypic effects, deletion analysis suggests an essential role for these units. Only mutations in the N-terminal nonconserved domain of PRP17 are synthetically lethal in combination with mutations in PRP16 and PRP18, two other gene products required for the second splicing reaction. A mutually allele-specific interaction between Prp17 and snr7, with mutations in U5 snRNA, was observed. We therefore suggest that the functional region of Prp17p that interacts with Prp18p, Prp16p, and U5 snRNA is the N terminal region of the protein.
PRP17基因产物是前体mRNA剪接反应第二步所必需的。该蛋白质的C端一半带有四个与β转导蛋白重复序列具有同源性的重复单元。三个温度敏感型prp17突变体中的错义突变定位于该蛋白质N端一半的一个区域。我们在体外产生了11个β转导蛋白重复单元处的错义等位基因，发现只有一个在体内影响功能。第四个重复单元处一个表型沉默的错义等位基因增强了第三个重复单元处一个等位基因所赋予的生长缓慢表型，表明这些结构域之间存在相互作用。尽管高度保守氨基酸中的许多错义突变缺乏表型效应，但缺失分析表明这些单元具有重要作用。只有PRP17的N端非保守结构域中的突变与PRP16和PRP18中的突变（剪接反应第二步所需的另外两个基因产物）组合时才具有合成致死性。观察到Prp17与snr7之间存在相互的等位基因特异性相互作用，U5 snRNA中有突变。因此，我们认为Prp17p与Prp18p、Prp16p和U5 snRNA相互作用的功能区域是该蛋白质的N端区域。
