Cryo-EM Structure of a Pre-catalytic Human Spliceosome Primed for Activation

Abstract

Little is known about the spliceosome's structure before its extensive remodeling into a catalytically active complex. Here, we report a 3D cryo-EM structure of a pre-catalytic human spliceosomal B complex. The U2 snRNP-containing head domain is connected to the B complex main body via three main bridges. U4/U6.U5 tri-snRNP proteins, which are located in the main body, undergo significant rearrangements during tri-snRNP integration into the B complex. These include formation of a partially closed Prp8 conformation that creates, together with Dim1, a 5' splice site (ss) binding pocket, displacement of Sad1, and rearrangement of Brr2 such that it contacts its U4/U6 substrate and is poised for the subsequent spliceosome activation step. The molecular organization of several B-specific proteins suggests that they are involved in negatively regulating Brr2, positioning the U6/5'ss helix, and stabilizing the B complex structure. Our results indicate significant differences between the early activation phase of human and yeast spliceosomes.

Mutations in spliceosome genes and therapeutic opportunities in myeloid malignancies

“…The region around the cryptic 3′ splice site coincides with an enrichment of adenosines that also appear to have stronger base‐pairing affinity with the cognate U2 snRNA relative to the region around the canonical BPS. Structural analyses of the human and yeast spliceosome in the RNA‐bound B‐activated Complex suggest that cancer‐associated mutations in SF3B1 change the charge and shape of the corresponding amino acid residues that results in direct disruption of the local interaction with pre‐mRNA . This results in a spatial shift in the pre‐mRNA by approximately 10 nucleotides, consistent with bioinformatic predictions.…”

Targeted gene insertion into Z chromosome of chicken primordial germ cells for avian sexing model development

“…Also, DNAJA1 has been related to positive regulation of virus replication in humans (42). SMU1 is also involved in pre-mRNA splicing as a component of the spliceosome and is required for normal mitotic spindle assembly and mitosis (43). Therefore, the modification of the intergenic region of DNAJA1 and SMU1 may disturb the expression of DNAJA1 and SMU1 in the genome-modified chickens.…”

Writing a wrong: Coupled RNA polymerase II transcription and RNA quality control

“…Additionally, this method provides the ability to investigate splicing regulation through intron retention, which was previously not possible due to the transient nature of these RNA species and mutations that had to be made for stabilization. Further advances in our understanding of splicing have occurred through recently solved structures characterizing the spliceosome in different forms (Agafonov et al, ; Bertram, Agafonov, Dybkov, et al, ; Bertram, Agafonov, Liu, et al, ; Finci et al, ; Galej et al, ; Nguyen et al, , ; Ohi, Ren, Wall, Gould, & Walz, ; Pomeranz Krummel, Oubridge, Leung, Li, & Nagai, ; R. Wan et al, ; Yan et al, ). More in‐depth reviews of structural studies of the spliceosome can be found in Fica and Nagai () and Nguyen et al ().…”