Domain interactions within the Ski2/3/8 complex and between the Ski complex and Ski7p.

Area of Science:

• Molecular Biology
• Yeast Genetics
• RNA Metabolism

Background:

• The Ski complex (Ski2p, Ski3p, Ski8p) is vital for cytoplasmic mRNA decay in yeast.
• Its interactions with other proteins, like Ski7p and the exosome, are key for degradation but poorly understood.

Purpose of the Study:

• To elucidate the interaction network within the Ski complex and with Ski7p.
• To determine the functional significance of these interactions in vivo.

Main Methods:

• Utilized a directed two-hybrid system to map protein-protein interactions.
• Employed coimmunoprecipitation experiments to validate interactions.
• Performed in vivo functional assays by mutating conserved residues in Ski2p.

Main Results:

• Ski3p acts as a scaffold protein within the Ski complex, binding Ski8p via its C terminus and Ski2p via its sub-C terminus.
• No direct interaction was observed between Ski2p and Ski8p.
• Ski7p interacts with the Ski complex through both Ski3p and Ski8p.
• Mutating the Ski2p helicase motif did not disrupt Ski7p interaction, suggesting Ski2p's enzymatic activity is not required for this binding.

Conclusions:

• Detailed the specific interaction interfaces within the yeast Ski complex.
• Established that Ski7p binding to the Ski complex is independent of Ski2p's helicase function.
• Provides a foundation for understanding the regulation of mRNA degradation pathways.