Sorting out the complexity of SR protein functions

been clear whether all of these activities occur during the removal of each intron+ Recent studies now suggest that all of the proposed SR protein functions are carried out during each round of splicing, and at least some of these functions are performed by independent SR protein molecules+ This review discusses recent advances in understanding the diverse functions of SR proteins in metazoan pre-mRNA splicing and presents a model that takes these new findings into account+ Although the reader should keep in mind that the activity of SR proteins in vivo can be influenced by modulating their subcellular localization, this review focuses on biochemical experiments that specifically address the mechanisms by which SR proteins directly function in the splicing reaction+ (The reader may also refer to related reviews recently published elsewhere (Tacke & Manley, 1999; Blencowe, 2000)+)