Reconstitution of 3' end processing of mammalian pre-mRNA reveals a central role of RBBP6

Area of Science:

• Molecular Biology
• RNA Processing
• Gene Expression

Background:

• Eukaryotic messenger RNA (mRNA) 3' end formation involves a two-step process: endonucleolytic cleavage and polyadenylation.
• This essential process is critical for mRNA stability, translation, and overall gene expression regulation.

Purpose of the Study:

• To define the minimal set of essential and stimulatory polypeptides required for mRNA 3' end processing.
• To elucidate the roles of specific proteins, such as RBBP6 and cleavage factors, in the cleavage and polyadenylation reaction.

Main Methods:

• Reconstitution of the RNA processing reaction using overproduced and purified proteins.
• In vitro cleavage assays dependent on the polyadenylation signal (AAUAAA).
• Structural analysis to determine protein-protein interactions, specifically RBBP6 with CPSF73.

Main Results:

• A minimal list of 14 essential and 2 stimulatory polypeptides for RNA processing was identified.
• The reconstituted system accurately cleaved pre-mRNA at the in vivo-utilized site.
• RBBP6 was found to be essential, interacting with the endonuclease CPSF73 via its DWNN domain. Cleavage Factor I was stimulatory but not essential. ATP binding, not hydrolysis, was required for cleavage by hClp1.

Conclusions:

• This study provides a comprehensive inventory of proteins involved in mRNA 3' end processing.
• The findings clarify the functional roles of key proteins and cofactors in the cleavage and polyadenylation machinery.
• Understanding these molecular mechanisms is fundamental for comprehending eukaryotic gene regulation.