Direct and indirect regulation of fetal globin transcript by RNA-binding protein IGF2BP1

Area of Science:

• Molecular Biology
• Developmental Biology
• Gene Regulation

Background:

• Hemoglobin switching, the transition from fetal hemoglobin (HbF) to adult hemoglobin (HbA), is crucial for development but its molecular control is not fully understood.
• RNA-binding proteins (RBPs) and epigenetic modifications like N-6 methyladenosine (m6A) are known regulators of gene expression during development.
• IGF2BP1, an m6A-binding protein, was previously implicated in regulating fetal globin genes (HBG1/2) indirectly by suppressing BCL11A.

Purpose of the Study:

• To elucidate the precise molecular mechanism by which IGF2BP1 regulates developmental hemoglobin expression.
• To investigate the potential direct interactions of IGF2BP1 with HBG1/2 transcripts.
• To determine if IGF2BP1's regulation of HBG1/2 is dependent on its known interaction with BCL11A.

Main Methods:

• Investigated IGF2BP1's interaction with HIC2 and its role as a BCL11A repressor.
• Utilized RNA-binding assays to assess direct binding of IGF2BP1 to HBG1/2 transcripts.
• Employed functional assays to evaluate the impact of IGF2BP1 on HBG1/2 translation, focusing on m6A modification sites.

Main Results:

• IGF2BP1 binds to and activates HIC2, a repressor of BCL11A.
• IGF2BP1 directly binds to HBG1/2 transcripts, promoting their translation in a BCL11A-independent manner.
• Specific m6A-modified sequences near the stop codon of HBG2 transcripts are essential for IGF2BP1-mediated positive regulation.

Conclusions:

• IGF2BP1 directly enhances fetal hemoglobin translation through interaction with HBG1/2 mRNA, revealing a novel regulatory pathway.
• This direct mechanism of IGF2BP1 action on globin transcripts offers new insights into hemoglobin switching.
• The findings suggest a direct physical link between heterochronic RBPs and globin transcripts, expanding our understanding of gene regulation in development.