Foot-and-mouth disease virus (FMDV) and other picornaviruses initiate translation of their
polyprotein cap-independently at an internal site of the positive-strand
viral RNA. This process is mediated by the
internal ribosome entry site (IRES), a highly structured cis-acting
RNA element that binds translation
initiation factors and ribosomal subunits. During their life cycle, picornaviruses induce proliferation of membrane structures involved in viral replication and an increase in membrane permeability probably facilitating virus progeny release. Here, I analyze the efficiency of association of the ribosomal subunits with the FMDV IRES
RNA at elevated
salt concentrations.
Potassium stimulates FMDV translation, whereas
sodium chloride concentrations up to 150 mM neither stimulate nor interfere with FMDV translation. Even high
potassium concentrations allow binding of the
viral RNA to ribosomes.
Chloride stimulates binding of ribosomes to the
viral RNA at the stage of 48S initiation complex formation and FMDV translation at concentrations up to 150 mM. Only at elevated concentrations, binding of ribosomal subunits and translation are inhibited by
chloride. However, FMDV start site selection is not influenced by
potassium salts. These results indicate that the association of the
viral RNA with ribosomal subunits is well adapted to high
salt conditions that are induced during
picornavirus infection.