Regulation of alternative splicing: more than just the ABCs

Alternative pre-mRNA splicing, the differential inclusion or exclusion of portions of a nascent transcript into the final protein-coding mRNA, is widely recognized to be a ubiquitous mechanism for controlling protein expression. Thus, understanding the molecular basis of alternative splicing is essential for deciphering post-transcriptional control of the genome. Pre-mRNA splicing in general is catalyzed by a large dynamic macromolecular machine known as the spliceosome. Notably, the recognition of the intron substrate by spliceosomal components and the assembly of these components to form a catalytic spliceosome occur through a network of highly combinatorial molecular interactions. Many, if not all, of these interactions are subject to regulation, forming the basis of alternative splicing. This minireview focuses on recent advances in our understanding of the diversity of mechanisms by which the spliceosome can be regulated so as to achieve precise control of alternative splicing under a range of cellular conditions.