Recognition of eukaryotic initiation factor 4G isoforms by picornaviral proteinases

Abstract

The leader proteinase (Lpro) of foot and mouth disease virus is a papain-like cysteine proteinase. After processing itself from the polyprotein, Lpro then cleaves the host protein eukaryotic initiation factor (eIf) 4GI, thus preventing protein synthesis from capped mRNA in the infected cell. We have investigated Lpro interaction with eIF4GI and its isoform, eIF4GII. Lpro, expressed as a catalytically inactive fusion protein with glutathione S-transferase, binds specifically to eIF4G isomers in rabbit reticulocyte lysates. Deletion and specific mutagenesis were used to map the binding domain on Lpro to residues 183-195 of the C-terminal extension and to residue Cys133. These residues of the C-terminal extension and Cys133 are adjacent in the crystal structure but lie about 25 Å from the active site. The region on eIF4GI recognized by the Lpro C-terminal extension was mapped to residues 640-669 using eIF4GI fragments generated by proteolysis or by in vitro translation. The Lpro cleavage site at Gly674 ↓ Arg675 was not necessary for binding. Similar experiments with human rhinovirus 2A proteinase (2Apro), a chymotrypsin-like cysteine proteinase that also cleaves eIF4G isoforms, revealed that 2Apro can also bind to eIF4GI fragments lacking its cleavage site. These experiments strongly suggest a novel interaction between picornaviral proteinases and eIF4G isoforms.