SUPPRESSION OF A CFTR PREMATURE STOP MUTATION IN A BRONCHIAL EPITHELIAL-CELL LINE

Cystic fibrosis (CF) is caused by mutations in the CF transmembrane co nductance regulator (CFTR) protein(1). While 70% of CF chromosomes car ry a deletion of the phenylalanine residue 508 (Delta F508) of CFTR, r oughly 5% of all CF chromosomes carry a premature stop mutation(2). We reported that the aminoglycoside antibiotics C-418 and gentamicin can suppress two premature stop mutations [a stop codon in place of glyci ne residue 542 (G542X) and arginine residue 553 (R553X)] when expresse d from a CFTR cDNA in HeLa cells(3). Suppression resulted in the synth esis of full-length CFTR protein and the appearance of a cAMP-activate d anion conductance characteristic of CFTR function. However, it was u nclear whether this approach could restore CFTR function in cells expr essing mutant forms of CFTR from the nuclear genome. We now report tha t G-418 and gentamicin are also capable of restoring CFTR expression i n a CF bronchial epithelial cell line carrying the CFTR W1282X prematu re stop mutation (a stop codon in place of tryptophan residue 1282). T his conclusion is based on the reappearance of cAMP-activated chloride currents, the restoration of CFTR protein at the apical plasma membra ne, and an increase in the abundance of CFTR mRNA levels from the W128 2X allele.