IGF2BP3 remodels the microRNA targeting landscape in MLL-AF4 leukemia

Area of Science:

• Molecular Biology
• Cancer Biology
• RNA Biology

Background:

• Insulin-like growth factor 2 mRNA binding protein 3 (IGF2BP3) is crucial for MLL-AF4-driven leukemogenesis.
• IGF2BP3's mechanism in amplifying oncogenic gene expression is not fully understood.

Purpose of the Study:

• To investigate the role of IGF2BP3 in modulating RNA-induced silencing complex (RISC) interactions.
• To elucidate how IGF2BP3 amplifies oncogenic gene expression in B-cell acute lymphoblastic leukemia (B-ALL).

Main Methods:

• Performed AGO2 miR-eCLIP in IGF2BP3 knock-out (I3KO) and control B-ALL cell lines.
• Analyzed chimeric miRNA-mRNA reads to assess differential miRNA occupancy.
• Conducted biochemical assays to confirm protein interactions.

Main Results:

• Identified 111 IGF2BP3-dependent AGO2 binding sites on 3'UTRs.
• Observed increased targeting by miR-181a in I3KO cells, suggesting IGF2BP3 restricts miR-181a-mediated repression.
• Confirmed direct competition between IGF2BP3 and AGO2-miRNA complexes for 3'-UTR binding.

Conclusions:

• IGF2BP3 promotes leukemogenesis by antagonizing RISC-mediated repression of oncogenic mRNAs.
• IGF2BP3 acts by competing with RISC complexes for binding to target 3'UTRs.
• This mechanism highlights IGF2BP3 as a potential therapeutic target in MLL-AF4-driven leukemia.