Aminoglycoside antibiotics are able to specifically bind the 5 '-untranslated region of thymidylate synthase messenger RNA

The translational initiation codon for thymidylate synthase (TS) mRNA is lo cated in a unique stem-loop structure which contains an internal cytosine-c ytosine (CC) bubble. This stem-loop structure is thought to be important in the regulation of TS translation, which is itself an important target for anticancer drugs, such as 5-fluorouracil, Internal bubble or bulge structur es are candidate receptors for the aminoglycoside antibiotics. It is shown here that aminoglycosides bind in a specific and saturable fashion with dis sociation constants of approximately 1 mu M to a TS mRNA site 1 construct a nd that the binding site for the aminoglycosides is located in the CC bubbl e region. In fact, the CC bubble, when grafted into other stem-loop structu res, confers aminoglycoside binding on them. These studies reveal an additi onal binding domain for aminoglycosides and also suggest how novel anti-can cer drags might be designed that affect TS mRNA translation rather than enz yme function.