The cap epitranscriptome: Early directions to a complex life as mRNA

Area of Science:

• Molecular Biology
• Epigenetics
• Neuroscience

Background:

• Messenger RNAs (mRNAs) undergo modifications, including 2"-O-methylation (cOMe) and N6-methylation (m6A), primarily at their 5' ends.
• These modifications are catalyzed by specific enzymes like cap methyltransferases (CMTrs), PCIF1, and the Mettl3/14 complex.
• Co-transcriptional introduction of these modifications influences gene expression, mRNA localization to synapses, and local translation.

Purpose of the Study:

• To explore the potential of heterogeneous transcription start sites in generating mRNA sequence diversity.
• To investigate how this diversity, combined with existing mRNA modifications (cOMe, m6A), could establish a novel layer of gene expression control.
• To understand the implications of these epigenetic marks in synaptic gene expression, learning, and memory.

Main Methods:

• Analysis of mRNA modifications, focusing on cap-adjacent nucleotides.
• Investigating the role of enzymes like PCIF1 and Mettl3/14 in mRNA methylation.
• Examining the impact of heterogeneous transcription start sites on mRNA sequence and function.

Main Results:

• Heterogeneous transcription start sites lead to sequence diversity at the mRNA 5' end.
• This diversity, alongside cOMe and m6A modifications, suggests a new mechanism for gene regulation.
• These modifications are implicated in synaptic function and higher brain processes like learning and memory.

Conclusions:

• mRNA 5' end modifications and transcription start site heterogeneity represent a significant layer of gene expression control.
• This regulatory mechanism is crucial for local gene expression in synapses.
• Such epigenetic codes may underlie lasting memories through synaptic plasticity.