Structure of the activated human minor spliceosome

Atomic structure of the minor spliceosome About 1% of the human genome contains the so-called U12-type introns, which are spliced by the minor spliceosome. Compared with the major spliceosome, the composition, assembly, functional states, activation, regulation, and structure of the minor spliceosome have been enigmatic. Bai et al. assembled the activated human minor spliceosome in an in vitro U12-type intron-splicing assay and determined the structure by cryo–electron microscopy at 2.9-angstrom resolution. They found a number of exciting and unanticipated features, including five new proteins that play an important role in the activated minor spliceosome. Science , this issue p. eabg0879