Alternative splicing of BCL-x is controlled by RBM25 binding to a G-quadruplex in BCL-x pre-mRNA

Area of Science:

• Molecular Biology
• RNA Splicing
• Cancer Therapeutics

Background:

• Alternative splicing of BCL-x pre-mRNA generates anti-apoptotic (Bcl-xL) and pro-apoptotic (Bcl-xS) isoforms.
• Dysregulation of Bcl-x isoforms is implicated in cancer chemoresistance, diabetes, and cardiac disorders.
• The splicing factor RBM25 regulates BCL-x alternative splicing, favoring Bcl-xS production upon overexpression.

Purpose of the Study:

• To elucidate the mechanism by which RBM25 controls BCL-x alternative splicing.
• To identify specific RNA structures and protein domains involved in RBM25-mediated splicing.
• To explore therapeutic strategies targeting the RBM25/BCL-x interaction for cancer treatment.

Main Methods:

• RNA-binding assays to confirm RBM25 interaction with BCL-x pre-mRNA.
• Identification of RNA G-quadruplex (rG4) structures within BCL-x pre-mRNA.
• Mutational analysis of RBM25 to identify critical functional domains (e.g., RE motif).
• Screening of small molecules (G4 ligands) for their effect on RBM25 binding and splicing outcomes.

Main Results:

• RBM25 directly binds to the GQ-2 rG4 structure in BCL-x pre-mRNA near the alternative 5' splice site.
• This RBM25/rG4 interaction is essential for promoting the production of the pro-apoptotic Bcl-xS isoform.
• The arginine-glutamate-rich (RE) motif of RBM25 is critical for this rG4 interaction.
• G4 ligands, including PhenDC3, PhenDH8, and PhenDH9, enhance RBM25 binding to GQ-2, promoting Bcl-xS and apoptosis.

Conclusions:

• The RBM25/GQ-2 rG4 interaction represents a novel mechanism controlling BCL-x alternative splicing.
• Targeting this interaction with small molecules offers a promising strategy to induce apoptosis in cancer cells.
• This approach could potentially re-sensitize chemoresistant tumors to therapeutic interventions.