DNA sequences of frameshift and other mutations induced by ICR-170 in yeast

ICR-170-induced mutations in the CYC1 gene of the yeast Saccharomyces cerevisiae were investigated by genetic and DNA sequence analyses. Genetic analysis of 33 cyc1 mutations induced by ICR-170 and sequence analysis of eight representatives demonstrated that over one-third were frameshift mutations that occurred at one site corresponding to amino acid positions 29-30, whereas the remaining mutations were distributed more-or-less randomly, and a few of these were not frameshift mutations. The sequence results indicate that ICR-170 primarily induces G.C additions at sites containing monotonous runs of three G.C base pairs. However, some (Formula: see text) sites within the CYC1 gene were not mutated by ICR-170. Thus, ICR-170 is a relatively specific mutagen that preferentially acts on certain sites with monotonous runs of G.C base pairs.