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. 2009 Mar 13;284(11):7165–7176. doi: 10.1074/jbc.M806461200

FIGURE 1.

FIGURE 1.

sng2-1/cut4-, cut4-533, and cut9-665 mutant exhibit two alternative states of expression of silent mat2 locus. A, sng2-1 mutant having the mat2-proximal silencer deleted (REIIΔ) exhibits light (L) and dark (D) colonies upon iodine staining, which are metastable and switch to the opposite state at a low rate. The rate of switching was determined according to Ref. 17. B, the light and dark states show low and high levels, respectively, of ura4 expression as monitored by serial dilution assay on plates lacking uracil or containing FOA. C, cut4-533 and cut9-665 mutants also exhibit the two epigenetic states of silencing in the strain background Msmto REIIΔ mat2::ura4, which show relatively less stability than the sng2-1 mutant histogram. D, the dark (D) and light (L) colonies exhibit high and low levels of ura4 transcripts, respectively. RT-PCR for ura4 and act1 as a negative control was carried out according to Singh et al. (41).