Mutation spectrum of spontaneous frameshift revertants in yeast using double-strand gap repair.
A mutation spectrum was constructed from a series of randomly isolated spontaneous His+ revertants of the frameshift mutant his4-38 in Saccharomyces cerevisiae. For each true revertant, a 438 bp region encompassing his4-38 on chromosome III was recovered into a shuttle vector by double-strand gap repair. Of the 45 independent His+ revertants sequenced, 44 were -1 base deletions and one revertant was a +2 base insertion. The -1 deletions exhibited a bimodal distribution. Of the bases encompassing the his4-38 region from +153-181, approximately 45% were not involved in a reversion event, although a -1 frameshift within this region will result in a viable His+ revertant. Approximately 49% of -1 events occurred within runs of 3 repeated bases. At these sites the strand-slippage model for frameshift mutation is supported. However, the -1 events occurring at sites of 2 repeated bases and the low frequency (2%) of +2 base insertions suggest that the transiently misaligned template model is a significant mechanism in reversion of his4-38. When the distribution of -1 events at repeated bases was discounted, a hotspot involving a -T at position +163 was resolved.
Plewa
M J
MJ
Institute for Environmental Studies, University of Illinois, Urbana-Champaign 61801.
Kalinowski
D P
DP
Larimer
F W
FW
D001483:Base Sequence; D004260:DNA Repair; D004271:DNA, Fungal / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics; D016368:Frameshift Mutation; D005821:Genetic Techniques; D005822:Genetic Vectors; D006639:Histidine / Q000235:genetics; D008969:Molecular Sequence Data; D009838:Oligodeoxyribonucleotides; D010957:Plasmids; D015183:Restriction Mapping; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D014170:Transformation, Genetic
D004271:DNA, Fungal; D009838:Oligodeoxyribonucleotides; D006639:Histidine