A natural riboswitch scaffold with self-methylation activity

Area of Science:

• Molecular Biology
• RNA Biology
• Biochemistry

Background:

• Methylation is a key RNA modification, crucial for cellular function.
• S-adenosylmethionine (SAM) is a primary methyl donor, with origins potentially linked to an RNA world.
• Riboswitches are RNA molecules that regulate gene expression, and ribozymes are catalytic RNA enzymes.

Purpose of the Study:

• To uncover a direct link between riboswitches and RNA methylation.
• To investigate the role of O6-methyl pre-queuosine (m6preQ1) in RNA modification.
• To explore the ancient origins of nucleic acid-mediated methylation.

Main Methods:

• Characterization of the interaction between m6preQ1 and a preQ1 class I riboswitch aptamer.
• Analysis of the site-specific methylation reaction occurring upon ligand binding.
• Investigation of the resulting RNA modification, 3-methylcytidine (m3C).

Main Results:

• A direct functional link between a riboswitch and RNA methylation was identified.
• The nucleobase m6preQ1 was found to bind to a preQ1 class I riboswitch aptamer.
• This binding event triggers the transfer of a methyl group from m6preQ1 to a specific cytidine within the RNA, forming m3C.

Conclusions:

• Nucleic acid-mediated methylation represents an ancient mechanism, potentially predating protein methyltransferases.
• This discovery offers insights into early RNA epigenetics.
• The findings may enable the development of novel, rationally designed riboswitch-based methylation tools.