Manceau Valérie, Kielkopf Clara L, Sobel André, Maucuer Alexandre
Institut National de la Santé et de la Recherche Médicale, UMR839, 17, rue du Fer à Moulin, F-75005 Paris, France.
J Mol Biol. 2008 Sep 5;381(3):748-62. doi: 10.1016/j.jmb.2008.06.026. Epub 2008 Jun 17.
The protein kinase KIS is made by the juxtaposition of a unique kinase domain and a C-terminal domain with a U2AF homology motif (UHM), a sequence motif for protein interaction initially identified in the heterodimeric pre-mRNA splicing factor U2AF. This domain of KIS is closely related to the C-terminal UHM domain of the U2AF large subunit, U2AF(65). KIS phosphorylates the splicing factor SF1, which in turn enhances SF1 binding to U2AF(65) and the 3' splice site, an event known to take place at an early step of spliceosome assembly. Here, the analysis of the subcellular localization of mutated forms of KIS indicates that the kinase domain of KIS is the necessary domain for its nuclear localization. As in the case of U2AF(65), the UHM-containing C-terminal domain of KIS is required for binding to the splicing factors SF1 and SF3b155. The efficiency of KIS binding to SF1 and SF3b155 is similar to that of U2AF(65) in pull-down assays. These results further support the functional link of KIS with splicing factors. Interestingly, when compared to other UHM-containing proteins, KIS presents a different specificity for the UHM docking sites that are present in the N-terminal region of SF3b155, thus providing a new insight into the variety of interactions mediated by UHM domains.
蛋白激酶KIS由一个独特的激酶结构域和一个带有U2AF同源基序（UHM）的C端结构域并列组成，U2AF同源基序是一种最初在异二聚体前体mRNA剪接因子U2AF中发现的蛋白质相互作用序列基序。KIS的这一结构域与U2AF大亚基U2AF(65)的C端UHM结构域密切相关。KIS使剪接因子SF1磷酸化，这反过来又增强了SF1与U2AF(65)及3'剪接位点的结合，这是已知在剪接体组装早期发生的事件。在此，对KIS突变形式的亚细胞定位分析表明，KIS的激酶结构域是其核定位的必要结构域。与U2AF(65)的情况一样，KIS含UHM的C端结构域是与剪接因子SF1和SF3b155结合所必需的。在下拉实验中，KIS与SF1和SF3b155的结合效率与U2AF(65)相似。这些结果进一步支持了KIS与剪接因子之间的功能联系。有趣的是，与其他含UHM的蛋白质相比，KIS对存在于SF3b155 N端区域的UHM对接位点具有不同的特异性，从而为UHM结构域介导的多种相互作用提供了新的见解。
