Critical cis-parameters influence STructure assisted RNA translation (START) initiation on non-AUG codons in...

Area of Science:

• Molecular Biology
• Genetics
• Bioinformatics

Background:

• Translation initiation in eukaryotes is a complex, regulated process involving cis-regulatory sequences and trans-acting factors like eukaryotic initiation factors (eIFs).
• A key step is the 43S pre-initiation complex scanning for the start codon to initiate ribosome assembly and protein synthesis.

Purpose of the Study:

• To investigate the role of downstream secondary structures in the STructure-Assisted RNA translation (START) mechanism for both AUG and non-AUG initiation.
• To determine the optimal conditions for downstream structures to promote non-AUG translation initiation.

Main Methods:

• Analysis of secondary structure stability and location relative to non-AUG codons.
• Genome-wide analysis of alternative translation initiation sites in Homo sapiens.
• Validation of the impact of downstream structures on translation initiation using selected upstream open reading frames (uORFs).

Main Results:

• Downstream secondary structures can promote non-AUG translation initiation by stalling the 43S particle and stabilizing codon-anticodon pairing.
• The required stability of these structures varies across different cell types.
• Approximately 25% of human alternative translation initiation sites possess a downstream structure capable of facilitating START, irrespective of the start codon.

Conclusions:

• Downstream RNA structures play a significant role in regulating translation initiation, particularly for non-AUG start codons via the START mechanism.
• The START mechanism is a conserved and widespread regulatory strategy in human translation.
• Understanding START provides insights into alternative translation and gene expression regulation.