Symmetric adenine methylation is an essential DNA modification in the early-diverging fungus Rhizopus microsporus

Area of Science:

• Epigenetics
• Molecular Biology
• Fungal Genomics

Background:

• N6-methyladenine (6mA) is a DNA modification typically found in prokaryotes, but its role in eukaryotes is emerging.
• The MT-A70 complex (MTA1c) is identified as the enzyme responsible for symmetric 6mA in Rhizopus microsporus.

Purpose of the Study:

• To investigate the essentiality and function of symmetric 6mA in the early diverging fungus Rhizopus microsporus.
• To elucidate the mechanisms by which 6mA regulates gene expression and influences chromatin structure.

Main Methods:

• Genetic manipulation to create absence of the MT-A70 complex (MTA1c).
• Chromatin analysis to assess nucleosome positioning and histone modifications (H3K4me3, H2A.Z).
• Gene expression profiling to determine the impact of 6mA on transcriptional regulation.

Main Results:

• Absence of MTA1c leads to a lethal phenotype in Rhizopus microsporus, demonstrating the essentiality of symmetric 6mA.
• Symmetric 6mA is found in 70% of genes, correlating with open euchromatic regions and specific histone marks.
• 6mA modification influences nucleosome positioning near transcription start sites, particularly for highly expressed genes.
• Downregulation of MTA1c alters 6mA levels, affecting nucleosome positioning, histone modifications, and subsequently gene expression.

Conclusions:

• Symmetric DNA 6mA is indispensable for the survival of the multicellular fungus Rhizopus microsporus.
• This epigenetic mark plays a crucial role in regulating gene expression through modulation of chromatin structure and histone modifications.
• The study establishes DNA 6mA as a key epigenetic regulator in a eukaryotic genome.