IRES-C11 is a specific inhibitor of translation that targets the internal ribosome entry site (IRES) of the c-MYC gene. It functions by blocking the interaction between heterogeneous nuclear ribonucleoprotein A1, a trans-acting factor required for c-MYC IRES activity, and its corresponding IRES. Notably, IRES-C11 does not inhibit the IRES activity of BAG-1, XIAP, and p53.

IRES-C11 (50 nM) significantly inhibits both cyclin D1 and c-MYC IRES activity. IRES-C11 treatment induces a significant shift in both cyclin D1 and c-MYC mRNA to monosomal/nonribosomal fractions, whereas actin mRNA distribution is unaffected. IRES-C11 inhibits both cyclin D1 and c-MYC IRES-mediated mRNA translation, leading to reductions in protein levels. Mechanistic studies with IRES-C11 reveal the binding of the inhibitors within the UP1 fragment of heterogeneous nuclear ribonucleoprotein A1.[1]