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Inducibility of gene conversion in Saccharomyces cerevisiae treated with MMS
Abstract:
At high survival levels (85%), point mutation and gene conversion frequencies were determined in strain D7 of Saccharomyces cerevisiae after treatment with methyl methanesulfonate (MMS) either after cells were incubated in complete medium before plating or following a split-dose protocol. It is shown that induction of gene conversion by MMS post-incubation leads to an additional enhancement in frequency. This increase is not observed for point mutation. By fractionation of the MMS dose (1 mM + 1 mM) with incubation in complete medium between the 2 doses the frequency of gene conversion is twice as high as with a single equal total dose (2 mM). This treatment does not modify the frequencies of point mutation. These data support the notion that an inducible recombinogenic function exists in wild-type yeast.
Insights
Methyl methanesulfonate (MMS) treatment enhances gene conversion frequency in yeast, particularly when split into multiple doses with recovery time. This suggests an inducible recombinogenic function in wild-type yeast.
Area of Science:
- Molecular and Cellular Biology
- Yeast Genetics
- DNA Repair Mechanisms
Background:
- Investigating the effects of genotoxic agents like methyl methanesulfonate (MMS) on DNA mutation and recombination.
- Understanding cellular responses to DNA damage in Saccharomyces cerevisiae (yeast).
Purpose of the Study:
- To determine point mutation and gene conversion frequencies in yeast strain D7 following MMS treatment.
- To evaluate the impact of post-incubation and split-dose MMS protocols on these frequencies.
- To explore the existence of an inducible recombinogenic function in wild-type yeast.
Main Methods:
- Treatment of Saccharomyces cerevisiae strain D7 with methyl methanesulfonate (MMS).
- Comparison of single-dose versus split-dose MMS treatment protocols.
- Incubation in complete medium before plating or between split doses.
- Quantification of point mutation and gene conversion frequencies at high survival levels (85%).
Main Results:
- Post-incubation following MMS treatment significantly enhances gene conversion frequency, but not point mutation frequency.
- A split-dose MMS protocol (1 mM + 1 mM with incubation) resulted in twice the gene conversion frequency compared to a single 2 mM dose.
- The split-dose treatment did not alter point mutation frequencies.
Conclusions:
- The findings support the existence of an inducible recombinogenic function in wild-type yeast.
- Cellular response to MMS involves mechanisms that preferentially enhance recombination over mutation under specific conditions.
- Fractionated dosing strategies can differentially modulate DNA repair and recombination pathways.