Cryo-EM structures of human m⁶A writer complexes.

Area of Science:

• Molecular Biology
• Structural Biology
• Epigenetics

Background:

• N⁶-methyladenosine (m⁶A) is the most prevalent RNA modification in eukaryotes.
• The m⁶A writer complex, crucial for this modification, comprises catalytic (MAC) and regulatory (MACOM) subunits.
• MACOM is essential for the enzymatic activity of the m⁶A writer.

Purpose of the Study:

• To determine the cryo-electron microscopy (cryo-EM) structures of the MACOM and MACOM-MAC complexes.
• To elucidate the molecular assembly and interaction mechanisms of the m⁶A writer complex.

Main Methods:

• Cryo-electron microscopy (cryo-EM) at 3.0-Å and 4.4-Å resolutions.
• Crosslinking mass spectrometry (XL-MS).
• GST pull-down assays, in vitro RNA binding, and methyltransferase activity assays.

Main Results:

• The core structure of MACOM comprises WTAP and VIRMA, with ZC3H13 influencing its conformation.
• A model for the MACOM-MAC complex reveals MACOM binds MAC primarily via WTAP and METTL3.
• In vitro assays confirm MACOM's role in assembling and activating the m⁶A writer complex.

Conclusions:

• Structural and biochemical data reveal the molecular basis for m⁶A writer complex formation and function.
• Understanding MACOM-MAC interactions provides insights into the regulation of m⁶A epitranscriptomic modification.