Structure of an active human histone pre-mRNA 3'-end processing machinery

Area of Science:

• Molecular Biology
• Structural Biology
• RNA Processing

Background:

• Metazoan histone pre-mRNA 3'-end processing utilizes U7 small nuclear ribonucleoprotein (snRNP).
• This machinery shares components with the canonical cleavage and polyadenylation complex.

Purpose of the Study:

• To reconstitute and determine the cryo-EM structure of the human histone pre-mRNA processing machinery.
• To elucidate the mechanism of activation and pre-mRNA cleavage.

Main Methods:

• Reconstitution of the active human histone pre-mRNA processing machinery using 13 recombinant proteins and two RNAs.
• Cryo-electron microscopy (cryo-EM) for structural determination.

Main Results:

• Determined the cryo-EM structure of the 13-protein, 2-RNA complex, revealing an asymmetrical amphora-like shape.
• Captured the pre-mRNA substrate within the endonuclease active site, poised for cleavage.
• Demonstrated that U7 snRNA recognition triggers extensive rearrangements in the cleavage module for activation.

Conclusions:

• The structure provides mechanistic insights into histone pre-mRNA 3'-end processing.
• Highlights the coordinated action of U7 snRNP and the cleavage module.
• Offers implications for understanding both canonical and snRNA-mediated 3'-end processing pathways.