Architecture of eukaryotic mRNA 3'-end processing machinery

Area of Science:

• Molecular Biology
• Biochemistry
• Structural Biology

Background:

• Eukaryotic precursor messenger RNAs (pre-mRNAs) undergo crucial 3'-end processing.
• The multiprotein cleavage and polyadenylation factor (CPF) mediates pre-mRNA cleavage, polyadenylation, and transcription termination.
• The precise coordination and assembly of CPF's enzymatic activities remain poorly understood.

Purpose of the Study:

• To investigate the structural organization of the yeast CPF.
• To elucidate the mechanism of mRNA 3'-end processing coordination by CPF.
• To determine the structure of the CPF polymerase module.

Main Methods:

• Electron cryomicroscopy (cryo-EM) was employed to determine the structure of the CPF polymerase module.
• In vitro reconstitution experiments were performed to validate functional aspects.
• Structural analysis focused on the arrangement of protein components within the polymerase module.

Main Results:

• The yeast CPF's nuclease, polymerase, and phosphatase activities are organized into three distinct modules.
• A 3.5-angstrom-resolution structure of the ~200-kilodalton CPF polymerase module was determined.
• The polymerase module features four β propellers, resembling other nucleic acid-binding protein complexes.
• The polymerase module facilitates the specific and efficient addition of polyadenylate tails.

Conclusions:

• The determined structure provides insights into the coordinated action of CPF enzymes.
• The polymerase module plays a key role in bringing together factors essential for accurate polyadenylation.
• This study advances our understanding of mRNA 3'-end processing regulation in eukaryotes.