Probing small ribosomal subunit RNA helix 45 acetylation across eukaryotic evolution

Area of Science:

• Molecular Biology
• RNA Biology
• Evolutionary Biology

Background:

• NAT10 enzyme catalyzes N4-acetylcytidine (ac4C) in eukaryotic RNA.
• SNORD13, a small nucleolar RNA, is implicated in guiding ac4C to 18S ribosomal RNA (rRNA).
• The precise role and evolutionary conservation of SNORD13-mediated rRNA acetylation remain unclear.

Purpose of the Study:

• To investigate the requirement of SNORD13 for 18S rRNA acetylation in human and zebrafish.
• To determine the functional significance of SNORD13-dependent ac4C modification in human cells.
• To explore the evolutionary landscape of SNORD13 and rRNA acetylation mechanisms across eukaryotes.

Main Methods:

• CRISPR-Cas9 mediated gene knockout to assess SNORD13 function.
• Biochemical assays to detect and quantify ac4C modification.
• Comparative genomic analysis to identify SNORD13 homologs in metazoans.
• Functional assays for cell growth, ribosome biogenesis, and translation.

Main Results:

• SNORD13 is essential for ac4C modification at a single site on human and zebrafish 18S rRNA.
• SNORD13-dependent ac4C is not required for human cell viability, ribosome biogenesis, translation, or development.
• Novel SNORD13 genes were identified across metazoans, including an atypical RNA in Drosophila melanogaster.
• Caenorhabditis elegans 18S rRNA lacks ac4C modification despite the presence of NAT10.

Conclusions:

• SNORD13-mediated 18S rRNA acetylation is dispensable for fundamental cellular processes in humans.
• The mechanisms and evolutionary trajectory of SNORD13-guided rRNA acetylation vary significantly across eukaryotic evolution.
• This study highlights the complex biological and evolutionary relevance of conserved RNA modifications.