Human DIMT1 generates N₂^6,6A-dimethylation-containing small RNAs

Area of Science:

• Molecular Biology
• RNA Modifications
• Biochemistry

Background:

• Dimethyladenosine transferase 1 (DIMT1) is a conserved enzyme responsible for N^6,6-dimethyladenosine (m₂^6,6A) methylation.
• DIMT1 is crucial for ribosome biogenesis, cell viability, and protein synthesis.
• The substrate specificity of DIMT1 beyond 18S rRNA remains largely unexplored.

Purpose of the Study:

• To investigate whether DIMT1 modifies small RNAs in addition to 18S rRNA.
• To determine the functional significance of DIMT1's catalytic activity on small RNA modifications.
• To explore the role of DIMT1 in human cancers, specifically acute myeloid leukemia.

Main Methods:

• Analysis of m₂^6,6A levels in small RNAs from cells expressing wildtype versus catalytically inactive DIMT1 variants (E85A, NLPY).
• Assessment of cell viability and protein synthesis in cells with altered DIMT1 activity.
• Examination of DIMT1 expression levels in human cancer tissues, including acute myeloid leukemia.

Main Results:

• DIMT1 generates m₂^6,6A modifications in small RNAs, not exclusively 18S rRNA.
• Catalytically inactive DIMT1 variants significantly reduced m₂^6,6A levels in small RNAs.
• DIMT1 expression is elevated in human cancers, and its downregulation in acute myeloid leukemia correlates with decreased m₂^6,6A in small RNAs.
• Cells with inactive DIMT1 exhibited reduced protein synthesis and viability.

Conclusions:

• DIMT1's enzymatic activity extends to the generation of m₂^6,6A modifications in small RNAs.
• Both 18S rRNA and small RNA m₂^6,6A modification by DIMT1 contribute to cellular health and gene expression.
• DIMT1's dysregulation in acute myeloid leukemia highlights its potential role in cancer pathogenesis.