Hertel K J, Maniatis T
Department of Molecular and Cellular Biology, Harvard University, 7 Divinity Avenue, Cambridge, MA 02138, USA.
Proc Natl Acad Sci U S A. 1999 Mar 16;96(6):2651-5. doi: 10.1073/pnas.96.6.2651.
Two distinct functions have been proposed for the serine-arginine (SR)-rich family of splicing factors. First, SR proteins are essential splicing factors and are thought to function by mediating protein-protein interactions within the intron during spliceosome assembly. Second, SR proteins bind to exonic enhancer sequences and recruit spliceosome components to adjacent introns. The latter activity is required for splice-site recognition and alternative splicing. Until now it has not been possible to determine whether the requirement for SR proteins in the basic splicing reaction is a secondary consequence of their exon-dependent recruitment function. Here we show that RNA substrates containing only 1 nt of exon sequence can undergo the first step of the splicing reaction in vitro and that this activity requires SR proteins. Thus, we provide direct evidence that SR proteins have both exon-independent and exon-dependent functions in pre-mRNA splicing.
对于富含丝氨酸-精氨酸（SR）的剪接因子家族，人们提出了两种不同的功能。首先，SR蛋白是必不可少的剪接因子，被认为在剪接体组装过程中通过介导内含子内的蛋白质-蛋白质相互作用发挥作用。其次，SR蛋白与外显子增强子序列结合，并将剪接体成分招募到相邻内含子。后一种活性是剪接位点识别和可变剪接所必需的。到目前为止，还无法确定在基本剪接反应中对SR蛋白的需求是否是其外显子依赖性招募功能的次要结果。在这里，我们表明仅含有1个核苷酸外显子序列的RNA底物在体外可以进行剪接反应的第一步，并且这种活性需要SR蛋白。因此，我们提供了直接证据，证明SR蛋白在mRNA前体剪接中具有外显子非依赖性和外显子依赖性功能。
