Microsatellite mutation rates are equivalent in normal and telomerase-immortalized human fibroblasts

Telomerase-expressing human fibroblasts generally have the same properties as normal cells, except that they have an indefinite life span in culture. We have introduced a dinucleotide repeat sequence into the telomerase-expre ssing hTERT-1604 cell line and characterized the rates and types of framesh ift mutations within this microsatellite. These data have been compared wit h those in diploid fibroblasts with a finite life span. The rates of mutati on were found to be similar in the two cell types, indicating that DNA mism atch repair and other cellular processes responsible for maintenance of mut ational stability are not disrupted by telomerase immortalization.