How Many Messenger RNAs Can Be Translated by the START Mechanism?

Area of Science:

• Molecular Biology
• Bioinformatics
• Genomics

Background:

• Translation initiation is crucial for protein synthesis and requires accurate AUG start codon recognition.
• The Structure Assisted RNA Translation (START) mechanism proposes using downstream RNA structures to guide start site selection.
• Stable secondary structures, optimally positioned after the start codon, can sterically hinder pre-initiation complex progression.

Purpose of the Study:

• To assess the prevalence and importance of the START mechanism in gene expression.
• To develop a bioinformatic tool for identifying stable RNA structures in coding sequences.
• To investigate the occurrence of START-associated structures across different life kingdoms.

Main Methods:

• Developed a bioinformatic tool to screen coding sequences for stable RNA structures.
• Analyzed a 50-nucleotide window (+16 to +65) downstream of the start codon.
• Screened eight bacterial and six eukaryotic genomes, including human and bacterial species.

Main Results:

• Found stable structures in 0.6–2.5% of eukaryotic coding sequences, with ~50% being G-quadruplexes.
• Identified 747 such structures in humans.
• Detected higher frequencies in Gram-positive bacteria (2.6–4.2%) than Gram-negative (0.2–2.7%), with rare G-quadruplexes in bacteria.

Conclusions:

• The START mechanism appears to be an ancient strategy for facilitating start codon recognition.
• This mechanism is utilized across diverse life forms, including bacteria and eukaryotes.
• The findings highlight the conserved role of RNA structures in regulating gene expression.