Decapping activators in Saccharomyces cerevisiae act by multiple mechanisms

Area of Science:

• Molecular Biology
• RNA Biology
• Biochemistry

Background:

• Eukaryotic mRNA degradation involves translation inhibition and decapping.
• Pat1, Scd6, Edc3, and Dhh1 are known to promote decapping in yeast.
• The precise mechanisms by which these factors promote decapping remain largely unknown.

Purpose of the Study:

• To elucidate the mechanisms by which Pat1, Scd6, Edc3, and Dhh1 promote mRNA decapping in yeast.
• To investigate the roles of these proteins in translation initiation and decapping enzyme activity.
• To map the interactions between these proteins and other components of the mRNA decay pathway.

Main Methods:

• In vitro translation assays using purified proteins.
• Analysis of decapping enzyme activity.
• Protein-protein interaction studies using purified components.

Main Results:

• Purified Scd6 and a Pat1 region directly repress translation initiation in vitro.
• Pat1 and Edc3 enhance decapping enzyme activity, while Dhh1 and Scd6 do not.
• Numerous direct interactions were identified between Pat1, Dcp1, Dcp2, Dhh1, Scd6, Edc3, Xrn1, and the Lsm1-7 complex.

Conclusions:

• Three classes of decapping activators exist: those repressing translation initiation and/or stimulating Dcp1/2.
• Pat1 plays a critical role in mRNA decay by sequentially inhibiting translation, recruiting decapping factors, and activating Dcp2.
• These findings provide a mechanistic framework for understanding mRNA decapping in yeast.