Molecular Architecture of the Multiprotein Splicing Factor SF3b

TLDR

SF3b is a multiprotein complex essential for accurate intron excision, functioning as part of the U2 snRNP and U11/U12 di‑snRNP to recognize the branch site in both major and minor spliceosomes. Cryo‑EM at <10 Å resolution revealed the human SF3b architecture, locating the p14 RNA‑recognition motif in the central cavity and the 22‑repeat helical SF3b155 shell surrounding it.

Abstract

The splicing factor SF3b is a multiprotein complex essential for the accurate excision of introns from pre-messenger RNA. As an integral component of the U2 small nuclear ribonucleoprotein (snRNP) and the U11/U12 di-snRNP, SF3b is involved in the recognition of the pre-messenger RNA's branch site within the major and minor spliceosomes. We have determined the three-dimensional structure of the human SF3b complex by single-particle electron cryomicroscopy at a resolution of less than 10 angstroms, allowing identification of protein domains with known structural folds. The best fit of a modeled RNA-recognition motif indicates that the protein p14 is located in the central cavity of the complex. The 22 tandem helical repeats of the protein SF3b155 are located in the outer shell of the complex enclosing p14.