EMD-11975
Cryo-EM map of the transcribing Pol II-U1 snRNP complex with 155-nt RNA
EMD-11975
Single-particle3.9 Å
Deposition: 23/11/2020Map released: 20/01/2021
Last modified: 27/01/2021
Sample Organism:
Sus scrofa domesticus,
synthetic construct,
Homo sapiens
Sample: The transcribing RNA polymerase II-U1 snRNP complex with 155-nt RNA
Deposition Authors: Zhang S, Aibara S, Vos SM, Agafonov DE, Luehrmann R, Cramer P
Sample: The transcribing RNA polymerase II-U1 snRNP complex with 155-nt RNA
Deposition Authors: Zhang S, Aibara S, Vos SM, Agafonov DE, Luehrmann R, Cramer P
Structure of a transcribing RNA polymerase II-U1 snRNP complex.
Abstract:
To initiate cotranscriptional splicing, RNA polymerase II (Pol II) recruits the U1 small nuclear ribonucleoprotein particle (U1 snRNP) to nascent precursor messenger RNA (pre-mRNA). Here, we report the cryo-electron microscopy structure of a mammalian transcribing Pol II-U1 snRNP complex. The structure reveals that Pol II and U1 snRNP interact directly. This interaction positions the pre-mRNA 5' splice site near the RNA exit site of Pol II. Extension of pre-mRNA retains the 5' splice site, leading to the formation of a "growing intron loop." Loop formation may facilitate scanning of nascent pre-mRNA for the 3' splice site, functional pairing of distant intron ends, and prespliceosome assembly. Our results provide a starting point for a mechanistic analysis of cotranscriptional spliceosome assembly and the biogenesis of mRNA isoforms by alternative splicing.
To initiate cotranscriptional splicing, RNA polymerase II (Pol II) recruits the U1 small nuclear ribonucleoprotein particle (U1 snRNP) to nascent precursor messenger RNA (pre-mRNA). Here, we report the cryo-electron microscopy structure of a mammalian transcribing Pol II-U1 snRNP complex. The structure reveals that Pol II and U1 snRNP interact directly. This interaction positions the pre-mRNA 5' splice site near the RNA exit site of Pol II. Extension of pre-mRNA retains the 5' splice site, leading to the formation of a "growing intron loop." Loop formation may facilitate scanning of nascent pre-mRNA for the 3' splice site, functional pairing of distant intron ends, and prespliceosome assembly. Our results provide a starting point for a mechanistic analysis of cotranscriptional spliceosome assembly and the biogenesis of mRNA isoforms by alternative splicing.