Copper-binding proteins and exonic splicing enhancers and silencers

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• Eukaryotic DNA contains regulatory information beyond protein-coding sequences, including an "auxiliary" splicing code.
• Exonic splicing enhancers (ESEs) and silencers (ESSs) regulate messenger RNA precursor splicing.
• The interplay between protein sequence constraints and splicing regulation is not fully understood.

Purpose of the Study:

• To investigate how the splicing code responds to the need for specific amino acids, particularly metal-coordinating residues.
• To explore the relationship between copper-coordinating amino acids and the presence/absence of ESEs and ESSs.
• To understand the role of intron architecture in the efficient inclusion of exons encoding metal-binding residues.

Main Methods:

• Analysis of exonic splicing enhancer (ESE) and silencer (ESS) profiles in exons encoding copper-coordinating amino acids.
• Utilizing RNA sequencing and expressed sequence tags (EST) data to assess exon inclusion efficiency.
• Examining splice site strength, including polypyrimidine tracts, and intron architecture.

Main Results:

• Exons encoding copper-coordinating residues often lack ESEs and/or have excess ESSs.
• Despite altered splicing motifs, these exons show higher inclusion efficiency in mature messenger RNA compared to average exons.
• Stronger splice sites and specific intron features facilitate constitutive inclusion of these exons.
• ESE/ESS profiles for copper-coordinating residues resemble those for zinc but differ from calcium-coordinating residues.

Conclusions:

• The splicing code adapts to protein functional requirements, such as metal coordination.
• Intron architecture plays a crucial role in ensuring the expression of essential metal-binding residues.
• This study elucidates how evolutionary constraints on protein structure shape RNA splicing mechanisms.