Grc3 programs the essential endoribonuclease Las1 for specific RNA cleavage

Area of Science:

• Molecular Biology
• RNA Processing
• Enzymology

Background:

• Las1 is a recently identified endoribonuclease involved in precursor ribosomal RNA (rRNA) processing.
• The precise mechanism of Las1 action and its regulation are currently unknown.
• Dysfunction of Las1 is associated with severe human genetic disorders, underscoring its biological importance.

Purpose of the Study:

• To elucidate the mechanism of action and regulation of the Las1 endoribonuclease.
• To investigate the role of the binding partner Grc3 in Las1-mediated rRNA processing.
• To characterize the functional complex formed by Las1 and Grc3.

Main Methods:

• In vitro biochemical assays to assess Las1 endoribonuclease activity.
• Experiments in Saccharomyces cerevisiae to validate findings in a cellular context.
• Analysis of the quaternary structure and complex formation between Las1 and Grc3.

Main Results:

• Grc3 is essential for directing Las1 endoribonuclease activity to the specific C2 cleavage site.
• Las1 binding activates the Grc3 kinase activity specifically towards single-stranded RNA.
• Las1 and Grc3 form a tetrameric complex indispensable for efficient rRNA processing.

Conclusions:

• The study provides mechanistic insights into the regulation of Las1 endoribonuclease activity.
• The tetrameric Grc3/Las1 complex represents a unique protein-guided programmable endoribonuclease.
• The Grc3/Las1 complex shares functional similarities with RNaseL and Ire1, suggesting a conserved mechanism within the RNA splicing family.