Weeks K M, Cech T R
Department of Chemistry and Biochemistry, Howard Hughes Medical Institute, University of Colorado, Boulder 80309-0215, USA.
Cell. 1995 Jul 28;82(2):221-30. doi: 10.1016/0092-8674(95)90309-7.
The yeast mitochondrial group I intron b15 undergoes self-splicing at high Mg2+ concentrations, but requires the splicing factor CBP2 for reaction under physiological conditions. Chemical accessibility and UV cross-linking experiments now reveal that self-processing is slow because functional elements are not properly positioned in an active tertiary structure. Folding energy provided by CBP2 drives assembly of two RNA domains that comprise the catalytic core and meditates association of an approximately 100 nt 5' domain that contains the 5' splice site. Thus, the protein assembles RNA secondary structure elements into a specific three-dimensional array while the RNA provides the catalytic center. The division of labor between RNA and protein illustrated by this simple system reveals principles applicable to complex ribonucleoprotein assemblies such as the spliceosome and ribosome.
酵母线粒体I组内含子b15在高镁离子浓度下会进行自我剪接，但在生理条件下的反应需要剪接因子CBP2。化学可及性和紫外线交联实验现在表明，自我加工过程缓慢，因为功能元件在活性三级结构中没有正确定位。CBP2提供的折叠能量驱动了两个RNA结构域的组装，这两个结构域构成了催化核心，并介导了包含5'剪接位点的约100个核苷酸的5'结构域的结合。因此，蛋白质将RNA二级结构元件组装成特定的三维阵列，而RNA则提供催化中心。这个简单系统所展示的RNA和蛋白质之间的分工揭示了适用于诸如剪接体和核糖体等复杂核糖核蛋白组装体的原理。
