Boelens W, Scherly D, Jansen E J, Kolen K, Mattaj I W, van Venrooij W J
University of Nijmegen, Department of Biochemistry, The Netherlands.
Nucleic Acids Res. 1991 Sep 11;19(17):4611-8. doi: 10.1093/nar/19.17.4611.
Despite the great sequence similarity between U1A and U2B", both proteins do have a difference in RNA binding specificity and in the way they bind to their cognate RNAs. The U1A protein is able to bind in vitro U1 RNA independently of other factors. The U2B" protein binds specifically to U2 RNA in the presence of the U2A' protein only. We have compared the effect on RNA binding of multiple double point mutations at analogous positions in the U1A and U2B" protein. The results obtained show that amino acids at almost all of the analogous positions tested in U1A and U2B" have a comparable qualitative effect on RNA binding although the quantitative effect of mutations on U2B" is more severe than on U1A. Using U1A mutants with internal duplications a distinct area of the RNP motif of the U1A protein was identified which appears not to be directly involved in U1 RNA binding. In addition, roles of the highly conserved RNP1 and RNP2 sequences of the N-terminal RNP motif of the U1A protein, are investigated by replacing them with the analogous U1-70K sequences.
尽管U1A和U2B''之间存在很大的序列相似性，但这两种蛋白质在RNA结合特异性以及它们与同源RNA的结合方式上确实存在差异。U1A蛋白能够在体外独立于其他因子结合U1 RNA。U2B''蛋白仅在U2A'蛋白存在的情况下特异性结合U2 RNA。我们比较了U1A和U2B''蛋白中类似位置的多个双点突变对RNA结合的影响。所得结果表明，在U1A和U2B''中测试的几乎所有类似位置的氨基酸对RNA结合具有可比的定性影响，尽管突变对U2B''的定量影响比对U1A更严重。使用具有内部重复的U1A突变体，鉴定出U1A蛋白RNP基序的一个独特区域，该区域似乎不直接参与U1 RNA结合。此外，通过用类似的U1-70K序列替换U1A蛋白N端RNP基序中高度保守的RNP1和RNP2序列，研究了它们的作用。
