The nucleotide composition of microsatellites impacts both replication fidelity and mismatch repair in human colorectal cells

Introduction: Microsatellite instability is a key mechanism of colon carcinogenesis. We have previously studied mutations within a (CA)13 microsatellite using an EGFP-based reporter-assay that allows the distinction of replication errors and mismatch repair activity. Here we utilize this assay to compare mutations of mono- and dinucleotide repeats in human colorectal cells. Methods: HCT116 and HCT116+chr3 cells were stably transfected with EGFP-based plasmids harboring A10, G10, G16, (CA)13, and (CA)26 repeats. EGFP-positive mutant fractions were quantitated by flow cytometry, mutation rates were calculated, and…