The spliceosome: disorder and dynamics defined

•Evolutionarily young spliceosomal proteins have high intrinsic disorder.•Spliceosome assembly is reversible and can occur by multiple pathways.•Reversible post-translational modifications are key to spliceosome dynamics. Among the many macromolecular machines involved in eukaryotic gene expression, the spliceosome remains one of the most challenging for structural biologists. Defining features of this highly complex apparatus are its excessive number of individual parts, many of which have been evolutionarily selected for regions of structural disorder, and the remarkable compositional and conformation dynamics it must undertake to complete each round of splicing. Here we review recent advances in our understanding of spliceosome structural dynamics stemming from bioinformatics, deep sequencing, high throughput methods for determining protein–protein, protein–RNA and RNA–RNA interaction dynamics, single molecule microscopy and more traditional structural analyses. Together, these tools are rapidly changing our structural appreciation of this remarkably dynamic machine.