Integrative characterization of MYC RNA-binding function.

Area of Science:

• Molecular Biology
• Genetics
• Cancer Biology

Background:

• The MYC oncoprotein is a transcription factor known to regulate gene expression, cell proliferation, and metabolism.
• Emerging evidence suggests a role for MYC in interacting with RNA molecules, but the mechanisms and functional significance remain largely unexplored.

Purpose of the Study:

• To comprehensively characterize MYC as an RNA-binding protein.
• To elucidate the functional consequences of MYC-RNA interactions on MYC's biological activities.
• To identify the specific regions within MYC responsible for RNA binding.

Main Methods:

• Integrative characterization of MYC-RNA interactions across six cell lines.
• RNA depletion experiments to assess the impact on MYC chromatin occupancy.
• In vitro and in vivo assays to map RNA-binding domains and evaluate functional consequences.
• Site-directed mutagenesis to investigate the role of specific amino acid residues (KRR and RQRR motifs) in RNA binding.

Main Results:

• MYC binds to a wide range of RNAs, with a preference for guanosine-rich sequences.
• Depletion of cellular RNAs significantly reduces MYC's binding to chromatin.
• Specific conserved motifs (KRR and RQRR) in MYC's basic region are essential for RNA binding.
• Mutating the KRR motif abolishes RNA binding in vitro and in vivo without affecting DNA binding.
• Loss of RNA-binding function impairs MYC's chromatin association, gene activation, cell-cycle progression, and proliferation.

Conclusions:

• MYC functions as a direct RNA-binding protein, with specific motifs mediating this interaction.
• RNA binding is a critical determinant of MYC's chromatin occupancy and its oncogenic functions.
• These findings reveal a novel layer of regulation for MYC activity and open new avenues for therapeutic strategies targeting MYC-driven cancers.