Splicing is a crucial, ubiquitous and highly complex step in eukaryotic gene 
expression. The daunting complexity of the splicing reaction, although 
fascinating, has severely limited our understanding of its mechanistic details. 
Recent advances have begun to provide exciting new insights into the dynamic 
interactions that govern the function of the spliceosome, the multi-megadalton 
complex that performs splicing. An emerging paradigm is the presence of a 
succession of distinct conformational states, which are stabilized by an 
intricate network of interactions. Recent data suggest that even subtle changes 
in the composition of the interaction network can result in interconversion of 
the different conformational states, providing opportunities for regulation and 
proofreading of spliceosome function. Significant progress in proteomics has 
elucidated the protein composition of the spliceosome at different stages of 
assembly. Also, the increased sophistication and resolution of cryo-electron 
microscopy techniques, combined with high-resolution structural studies on a 
smaller scale, promise to create detailed images of the global structure of the 
spliceosome and its main components, which in turn will provide a plethora of 
mechanistic insights. Overall, the past two years have seen a convergence of 
data from different lines of research into what promises to become a holistic 
picture of spliceosome function.