Inosine induces context-dependent recoding and translational stalling

Area of Science:

• Molecular Biology
• RNA Biology
• Genetics

Background:

• RNA modifications regulate gene expression by influencing mRNA processing, translation, and stability.
• Inosine, a prevalent modification in metazoan mRNA, results from adenosine deamination by ADAR1 or ADAR2.
• Inosine is generally presumed to be recognized as guanosine during cellular processes, including translation.

Purpose of the Study:

• To systematically investigate the ribosomal decoding of inosine in mRNA.
• To determine the fidelity and context-dependency of inosine interpretation by the ribosome.
• To explore the impact of inosine on ribosome behavior and translational efficiency in vivo.

Main Methods:

• Systematic testing of ribosomal decoding using mass spectrometry.
• Analysis of ribosome profiling data from human tissues.
• Mass spectrometry to detect inosine-mediated ribosome stalling.

Main Results:

• Inosine is primarily decoded as guanosine, but can also be interpreted as adenosine and, rarely, uracil.
• The decoding of inosine as adenosine or uracil is context-dependent.
• Inosine induces ribosome stalling, particularly when multiple inosine modifications occur within a codon, which is confirmed in human tissues.

Conclusions:

• This study provides the first comprehensive and unbiased assessment of inosine decoding by ribosomes.
• Inosine exhibits novel and unexpected decoding patterns, expanding the coding potential of mRNA.
• Inosine modifications significantly influence translational efficiency and introduce context-dependent variations in protein synthesis.