CFTR and cystic fibrosis: Here we present results demonstrating that (i) RFC termination activity has a strong dependence on the sequence context of PTCs found in patient mRNA sequences encoding CF transmembrane conductance regulator (CFTR) and fibrillin1 (FBN1), causing CF and Marfan syndrome, respectively; (ii) sequence dependent RFC activity correlates significantly with ataluren inhibition of termination and stimulation of readthrough; and (iii) combinations of ataluren and either of the nonsense suppressors ACE-tRNAArg and G418 have additive and occasionally synergistic effects on readthrough.