Figure 5.

Mutation of genes involved in maintaining euchromatin-heterochromatin boundaries suppresses the phenotypes of hst3Δ hst4Δ mutants. (A and B) Mutations of YTA7 or RSC2 but not RSC1 partially suppress the temperature sensitivity of hst3Δ hst4Δ mutants. Fivefold serial dilutions of cells carrying a centromeric plasmid expressing URA3 and HST3 were spotted on the indicated medium and grown at either 25 or 37°. (C) The sensitivity of hst3Δ hst4Δ mutants to MMS is partially rescued by rsc2∆ or yta7∆ mutations. Fivefold serial dilutions of cells were spotted onto YPD medium lacking or containing MMS and incubated at 25°. (D) The suppressor effect of sas2∆ and H4K16R mutations on the temperature sensitivity of hst3∆ hst4∆ cells does not require SIR2. Cells were treated as in A. (E) Constitutive expression of silent mating loci genes does not suppress the temperature sensitivity of hst3∆ hst4∆ cells. MATa hst3∆ hst4∆ cells harboring plasmids expressing either MATa or MATα genes and a centromeric plasmid expressing URA3 and HST3 were spotted on the indicated medium and grown at either 25 or 37°.