G3BP1 interacts directly with the FMDV IRES and negatively regulates translation

Area of Science:

• Virology
• Molecular Biology
• Biochemistry

Background:

• RNA-protein interactions are crucial for picornavirus internal ribosome entry site (IRES) function.
• Understanding these interactions is key to deciphering viral replication mechanisms.

Purpose of the Study:

• To investigate the role of Ras GTPase SH3 domain binding protein 1 (G3BP1) in the IRES activity of foot-and-mouth disease virus (FMDV).
• To elucidate the molecular mechanisms underlying G3BP1's interaction with FMDV IRES and its effect on translation.

Main Methods:

• RNA electrophoretic mobility-shift assays (EMSA) were used to analyze G3BP1 binding to FMDV IRES RNA.
• Interaction studies were performed with G3BP1's binding partners, including polypyrimidine tract-binding protein and translation initiation factor 4B (eIF4B).
• FMDV infection was used to study G3BP1 cleavage and the effects of its fragments on translation.

Main Results:

• G3BP1 directly binds to three distinct sequences within the FMDV IRES element.
• G3BP1 binding to IRES domain 5 is enhanced by an upstream hairpin structure.
• G3BP1 interacts with polypyrimidine tract-binding protein and eIF4B via its C-terminal region.
• FMDV infection leads to G3BP1 cleavage into Ct-G3BP1 and Nt-G3BP1 fragments, both inhibiting cap- and IRES-dependent translation, with Ct-G3BP1 showing stronger inhibition.
• G3BP1 binding reduces the local flexibility of the IRES element, correlating with its inhibitory effect.

Conclusions:

• G3BP1 possesses significant IRES-binding capacity.
• G3BP1 functions as a translation inhibitor for FMDV.
• Cleavage of G3BP1 during FMDV infection generates fragments that further modulate translation, impacting viral replication.