[Binding of the IRES of hepatitis C virus RNA to the 40S ribosomal subunit: role of protein p40].

Ribosomal protein p40 is a structural component of the 40S ribosomal subunit, which is partially homologuos to prokaryotic ribosomal protein S2 and has a long eukaryote-specific C-terminal region. In the present work, we have studied the binding of the Internal Ribosome Entry Site (IRES) of the hepatitis C virus (HCV) RNA to the 40S ribosomal subunit either deficient on protein p40, or saturated with the recombinant p40, or pre-bound to monoclonal antibodies (MAB) 4F6 against p40. It was shown that the apparent association constant of HCV IRES binding to 40S subunits directly depends on p40 content in the subunits. Binding of MAB 4F6 against p40 to 40S subunits prevented the HCV IRES binding by the subunits and blocked translation of the IRES-containing RNA in cell-free translation system. The data obtained point to the involvement of the ribosomal protein p40 in the binding of the HCV IRES by ribosomes and therefore in initiation of translation of RNA of this virus.

[Binding of human ribosomal protein p40 and its truncated mutants to the small ribosomal subunit].

Ribosomal protein SA (rpSA) or p40 is a structural element of the small subunit of the eukaryotic ribosome. N-terminal and central parts of the protein are homologous to prokaryotic rpS2 whereas its C-terminal part is eukaryote specific. In this study we showed that samples of 40S ribosomal subunits isolated from full-term human placenta are variably deficient in the rpSA content. To reveal rpSA ability to bind to human 40S ribosomal subunits, recombinant rpSA and its mutant forms with N- and C-terminal deletions have been synthesized. It was shown that both full-size and truncated from the N-terminus proteins were able to bind to the 40S subunits whereas the mutant truncated from C-terminus was not.