Mycobacteria Emerge as Leaders in Leaderless Translation.

Area of Science:

• Microbiology
• Molecular Biology
• Genetics

Background:

• Ribosome assembly and mRNA translation initiation typically depend on the 5' untranslated region (UTR).
• Leaderless messenger RNAs (mRNAs) lack a 5' UTR, posing a challenge for translation initiation.
• While rare and poorly translated in *Escherichia coli*, leaderless mRNAs are abundant and well-translated in certain bacterial groups, termed 'leaderless adept'.

Purpose of the Study:

• To investigate the characteristics of leaderless mRNAs in mycobacteria, a leaderless-adept bacterial clade.
• To explore the mechanisms underlying the efficient translation of leaderless mRNAs.
• To provide a foundation for understanding alternative translation initiation modes in diverse bacteria.

Main Methods:

• Analysis of native mycobacterial mRNAs.
• Expression of plasmid-borne reporter constructs in mycobacteria.
• Review of transcription profiling data identifying leaderless-adept bacteria.

Main Results:

• Mycobacteria are identified as leaderless-adept, possessing abundant and well-translated leaderless mRNAs.
• Criteria defining leaderless mRNA features in mycobacteria have been established.
• The study highlights the existence of efficient, alternative translation initiation pathways.

Conclusions:

• Leaderless mRNAs represent a significant mode of gene expression in certain bacteria, challenging canonical translation models.
• Mycobacteria serve as valuable models for studying leaderless mRNA translation.
• Further research in leaderless-adept bacteria will elucidate fundamental mechanisms of translation initiation.