7OQB

The U2 part of Saccharomyces cerevisiae spliceosomal pre-A complex (delta BS-A ACT1)

Summary for 7OQB

• Entry DOI: 10.2210/pdb7oqb/pdb
• EMDB information: 13028
• Descriptor: U2 snRNP component HSH155, RDS3 complex subunit 10, U2 small nuclear ribonucleoprotein A', ... (21 entities in total)
• Functional Keywords: s. cerevisiae, pre-a complex, prp5, u1 snrnp, u2 snrnp, prespliceosome, splicing
• Biological source: Saccharomyces cerevisiae (Baker's yeast); More
• Total number of polymer chains: 21
• Total formula weight: 1194074.13

Authors

Zhang, Z.,Rigo, N.,Dybkov, O.,Fourmann, J.,Will, C.L.,Kumar, V.,Urlaub, H.,Stark, H.,Luehrmann, R. (deposition date: 2021-06-03, release date: 2021-08-11, Last modification date: 2024-07-17)

Primary citation

Zhang, Z.,Rigo, N.,Dybkov, O.,Fourmann, J.B.,Will, C.L.,Kumar, V.,Urlaub, H.,Stark, H.,Luhrmann, R.
Structural insights into how Prp5 proofreads the pre-mRNA branch site.
Nature, 596:296-300, 2021

PubMed Abstract: During the splicing of introns from precursor messenger RNAs (pre-mRNAs), the U2 small nuclear ribonucleoprotein (snRNP) must undergo stable integration into the spliceosomal A complex-a poorly understood, multistep process that is facilitated by the DEAD-box helicase Prp5 (refs. ). During this process, the U2 small nuclear RNA (snRNA) forms an RNA duplex with the pre-mRNA branch site (the U2-BS helix), which is proofread by Prp5 at this stage through an unclear mechanism. Here, by deleting the branch-site adenosine (BS-A) or mutating the branch-site sequence of an actin pre-mRNA, we stall the assembly of spliceosomes in extracts from the yeast Saccharomyces cerevisiae directly before the A complex is formed. We then determine the three-dimensional structure of this newly identified assembly intermediate by cryo-electron microscopy. Our structure indicates that the U2-BS helix has formed in this pre-A complex, but is not yet clamped by the HEAT domain of the Hsh155 protein (Hsh155), which exhibits an open conformation. The structure further reveals a large-scale remodelling/repositioning of the U1 and U2 snRNPs during the formation of the A complex that is required to allow subsequent binding of the U4/U6.U5 tri-snRNP, but that this repositioning is blocked in the pre-A complex by the presence of Prp5. Our data suggest that binding of Hsh155 to the bulged BS-A of the U2-BS helix triggers closure of Hsh155, which in turn destabilizes Prp5 binding. Thus, Prp5 proofreads the branch site indirectly, hindering spliceosome assembly if branch-site mutations prevent the remodelling of Hsh155. Our data provide structural insights into how a spliceosomal helicase enhances the fidelity of pre-mRNA splicing.

PubMed: 34349264
DOI: 10.1038/s41586-021-03789-5

Experimental method

ELECTRON MICROSCOPY (9 Å)