Fig. 1.
Schematic drawing of FMDV Lpro self-processing and eIF4G cleavage. (A) The FMDV RNA genome is shown as a black line, the single open reading frame as a box with the names of the mature proteins and the position of the IRES. Lpro, being expressed either as Labpro or Lbpro, is indicated in red. (B) Synthesis of the polyprotein from the FMDV genome showing that Lbpro can either be freed by an intramolecular or intermolecular reaction. sLbpro (shown in orange) is generated by self-processing at the C-terminus of Lbpro. (C) The effect of eIF4G cleavage by Lbpro or sLbpro. The cellular mRNA is shown as a black line with the cap structure as a filled circle. Lbpro and sLbpro are shown in red and orange, respectively. The 40S ribosomal subunit, the polyA-binding protein (PABP), eIF4G, eIF4E, eIF4A and eIF3 are shown in different shades of grey. Following cleavage of eIF4G by Lbpro or sLbpro, the capped mRNA is no longer connected to the 40S subunit and cannot be translated. In contrast, the viral RNA can bind to the C-terminal fragment of eIF4G and thus to the 40S subunit via eIF3.