Secondary structure is required for 3' splice site recognition in yeast

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• Gene splicing regulation is complex, influenced by higher-order RNA structures.
• These structures can mask splicing signals or alter exon recognition.
• Understanding these mechanisms is crucial for deciphering gene expression.

Purpose of the Study:

• To investigate the role of RNA secondary structures in Saccharomyces cerevisiae intron splicing.
• To determine how specific mutations affect intron splicing efficiency.
• To explore the potential for structure-based mechanisms in 3' splice site recognition.

Main Methods:

• RNA structure prediction using RNAfold.
• In-line probing to analyze RNA structures.
• Site-directed mutagenesis of yeast introns (COF1 and UBC13).
• Analysis of splicing efficiency in modified introns.

Main Results:

• A G to A substitution in the COF1 intron disrupted a stem-loop structure, impairing splicing.
• Intramolecular structures were found to reduce the distance between the branch point (BP) and 3' splice site (3'ss), masking the 3'ss.
• Similar structural requirements were observed for UBC13 intron splicing.
• Stable structures were predicted for distant BP introns across Saccharomycotina species.

Conclusions:

• Pre-mRNA secondary structures play a critical role in regulating intron splicing.
• Intramolecular structures can mediate 3' splice site recognition for the second splicing step.
• A structure-based mechanism for splice site recognition exists in yeast and related species.