Characterization of Cwc2, U6 snRNA, and Prp8 interactions destabilized by Prp16 ATPase at the transition between the first and second steps of splicing

Structural representation of spliceosomal components involved in the first-to-second steps transition. (A) Structure of S. cerevisiae spliceosome immediately after branching (5LJ5) (Galej et al. 2016). Spliceosome factors involved in the transition between the first and second steps are shown in color: Prp16 (pink), Isy1 (blue), Ecm2 (light green), U6–U2 helix Ia and the catalytic triplex (red/green), U2 stem IIa/IIc (green), U6-ISL and U6-₄₁AACAAU₄₆ (red), Cwc2 (orange), and Prp8 N-terminal domain (purple). Location of cwc2, U6, and prp8 alleles suppressing prp16-302 growth defects described in this paper are marked by spheres. (B) Schematic representation of U6 (red), U2 (green), and pre-mRNA (gray) at the catalytic center of the spliceosome. Base-pair interactions altered by Prp16 action are depicted.