[Translational control by the poly(A) binding protein: a check for mRNA integrity]

Area of Science:

• Molecular Biology
• Biochemistry
• Genetics

Context:

• Eukaryotic mRNA translation is a fundamental biological process.
• The 5' cap and 3' poly(A) tail of mRNA play critical roles in translation initiation.
• A ribonucleoprotein complex, including poly(A) binding protein (PABP), eIF4E, and eIF4G, mediates the interaction between the 5' cap and 3' poly(A) tail.

Purpose:

• To elucidate the intricate mechanisms of mRNA translation enhancement.
• To define the role of PABP in translation initiation and regulation.
• To investigate the function of PABP-interacting proteins, Paip1 and Paip2, in modulating translation.

Summary:

• The 5' cap and 3' poly(A) tail of eukaryotic mRNA synergistically enhance translation through a ribonucleoprotein network.
• This network, involving PABP, eIF4E, and eIF4G, stabilizes the 5' cap-binding protein complex, facilitating ribosome initiation complex formation.
• PABP is identified as a canonical initiation factor, essential for both cap-dependent and internal ribosomal entry site (IRES)-mediated translation.
• Paip1 enhances translation, while Paip2 inhibits it by disrupting PABP-poly(A) interactions and competing with eIF4G binding.

Impact:

• Establishes PABP as a central player in translation initiation, beyond its known role in mRNA stability.
• Provides a deeper understanding of the "closed-loop" model of translation and its regulation.
• Highlights the opposing roles of Paip1 and Paip2 in controlling protein synthesis, offering potential targets for therapeutic intervention.