Ikawa Yoshiya, Sasaki Kenta, Tominaga Hiroyuki, Inoue Tan
Graduate School of Biostudies, Kyoto University, Kyoto 606-8502, Japan.
J Biochem. 2003 May;133(5):665-70. doi: 10.1093/jb/mvg085.
The P5 or P7 extensions in the group I intron ribozyme serve as "modular activator units" by stabilizing the conserved core of the ribozyme. The P5 extension of a group IC1 intron was introduced to a barely active group IA2 intron lacking its original P7 extension. The inserted P5 extension significantly activated the chimeric construct. Because the CYT-18 protein factor is also known to activate mutant group IA2 and IC1 introns lacking their P7 and P5 extensions, respectively, the RNA and protein activator units function in an analogous manner.
I组内含子核酶中的P5或P7延伸序列通过稳定核酶的保守核心，作为“模块化激活单元”发挥作用。将I C1组内含子的P5延伸序列引入到一个几乎没有活性、缺乏其原始P7延伸序列的I A2组内含子中。插入的P5延伸序列显著激活了嵌合构建体。由于已知CYT-18蛋白因子也分别激活缺乏其P7和P5延伸序列的I A2组和I C1组突变内含子，因此RNA和蛋白质激活单元以类似的方式发挥作用。
