eIF4G2 balances its own mRNA translation via a PCBP2-based feedback loop.

Area of Science:

• Molecular Biology
• Gene Regulation
• RNA-binding proteins

Background:

• Poly(rC)-binding protein 2 (PCBP2, also known as hnRNP E2) is a highly abundant RNA-binding protein in mammalian cells, with seven human isoforms.
• PCBP2 is known to bind 3'-untranslated regions (3'-UTRs) of mRNAs, influencing translation and stability.
• The functional impact of PCBP2 binding to 5'-UTRs remains largely unexplored.

Purpose of the Study:

• To investigate the role of PCBP2 isoforms in regulating gene expression through 5'-UTR interactions.
• To elucidate the functional consequences of PCBP2 binding to the 5'-UTRs of specific target mRNAs.
• To explore potential regulatory feedback loops between PCBP2 and translation initiation factors.

Main Methods:

• In vitro translation assays.
• Cell-based experiments in cultured cells.
• Analysis of mRNA-protein interactions with 5'-UTRs.
• Investigation of feedback mechanisms involving PCBP2 and eIF4G2.

Main Results:

• PCBP2 isoform f binds to the 5'-UTRs of eIF4G2 and Cyclin I mRNAs, inhibiting their translation.
• PCBP2 isoform e selectively inhibits Cyclin I translation.
• eIF4G2 is involved in the cap-dependent translation of PCBP2 mRNA.
• A novel feedback loop is identified where PCBP2 and eIF4G2 regulate each other's expression.

Conclusions:

• Specific PCBP2 isoforms can directly regulate gene expression by interacting with mRNA 5'-UTRs.
• PCBP2 isoform f plays a significant role in translational control of eIF4G2 and Cyclin I.
• A reciprocal regulatory relationship exists between PCBP2 and eIF4G2, mediated by translation initiation and RNA-binding.
• This study reveals a new mechanism of gene expression regulation involving RNA-binding proteins and translation factors.