The code within the code: microRNAs target coding regions.

Area of Science:

• Genomics and Molecular Biology
• Bioinformatics and Computational Biology
• RNA Biology and Gene Regulation

Background:

• The genetic code's redundancy allows for potential secondary information storage within coding sequences.
• MicroRNAs (miRNAs) are typically known to regulate gene expression by targeting 3' untranslated regions (UTRs).
• Evolutionary conservation is a key indicator of functional importance in genomic sequences.

Purpose of the Study:

• To computationally identify functional motifs, including miRNA binding sites, within coding regions using evolutionary conservation.
• To investigate the functional relevance of miRNA binding sites located within coding sequences.
• To explore the positional effects and potential mechanisms influencing miRNA binding site effectiveness.

Main Methods:

• Genome-wide computational screening for conserved functional motifs within protein-coding regions.
• Analysis of published proteomics data to assess the functional impact of coding region miRNA binding sites.
• Examination of the positional distribution and conservation patterns of miRNA binding sites.

Main Results:

• Highly conserved motifs were identified within coding regions, including known and novel motifs, and target sites for microRNAs.
• Proteomics data supports a functional role for coding region miRNA binding sites, albeit with weaker effects than 3' UTR sites.
• A positional bias was observed, with greater conservation at the 3' end of coding regions and both ends of 3' UTRs.

Conclusions:

• MicroRNA binding sites can be functionally relevant within coding sequences, expanding their known regulatory roles.
• The effectiveness of miRNA binding sites may be influenced by transcript localization, proximity to regulatory elements (poly(A) tail, 5' cap), and RNA-binding proteins.
• Increased miRNA conservation near stop codons suggests potential involvement in nonsense-mediated decay pathways.