Cryo-EM has been applied extensively by Shi et al to elucidate the near-/atomic structure of spliceosome in both yeast and humans. The molecular framework of spliceosome at near-atomic-resolution demonstrates Spp42 component of U5 snRNP forms a central scaffold and anchors the catalytic center in yeast. The atomic structure of the human spliceosome illustrates the step II component Slu7 adopts an extended structure, poised for selection of the 3'-splice site. All five metals (assigned as Mg2+) in the yeast complex are preserved in the human complex.