Human G3BP1 interacts with beta-F1-ATPase mRNA and inhibits its translation

Area of Science:

• Cell Biology
• Molecular Biology
• Biochemistry

Background:

• Post-transcriptional regulation of nuclear-encoded mitochondrial proteins is crucial for cell physiology.
• The mRNA for mitochondrial H(+)-ATP synthase subunit beta (ATP5B) forms a ribonucleoprotein complex (beta-F1-RNP) subject to translational control.
• Downregulation of ATP5B is common in human carcinomas, suggesting its regulatory mechanisms are relevant to cancer.

Purpose of the Study:

• To investigate the molecular composition of the human beta-F1-RNP.
• To identify RNA-binding proteins associated with ATP5B mRNA.
• To elucidate the role of these proteins in translational control and cancer.

Main Methods:

• Affinity chromatography and protein sequencing to identify RNA-binding proteins (RNABPs).
• Immunoprecipitation and fluorescent in-situ hybridization to confirm protein-mRNA interactions.
• RNA-bridged trimolecular fluorescence complementation (TriFC) and microscopy to localize interactions and complexes.

Main Results:

• Nine RNABPs were identified in the beta-F1-RNP.
• Endogenous Ras-GAP SH3 binding protein 1 (G3BP1) directly interacts with ATP5B mRNA.
• G3BP1 binds to the 3'-UTR of ATP5B mRNA within cytoplasmic RNA granules, inhibiting translation initiation.
• The beta-F1-RNP is localized to the mitochondrial periphery.

Conclusions:

• G3BP1 is a key regulator of ATP5B mRNA translation.
• G3BP1's inhibitory role in translation supports its involvement in the cancer-associated glycolytic switch.
• Understanding these regulatory mechanisms offers insights into cancer biology and potential therapeutic targets.