Figure 4.

Circumventing the effects of LOH at MET15. (A) For all phenotypically Met⁻ deletion strains that were met15Δ/met15Δ by PCR analysis, the met15Δ::kanMX4/met15Δ0 from the deletion strain collection was used as the wild-type control on SC-ile-val + SMM (2 µg/ml shown) containing medium. Cells were treated as in Figure 3A. As an example, the RBG1/rbg1Δ strain is not significantly more SMM-sensitive than the met15Δ::kanMX4/met15Δ0 control strain. In contrast, the VMA11/vma11Δ and HFI1/hfi1Δ strains are significantly more SMM-sensitive than the control. (B) Removal of methionine and cysteine from the growth medium reduces the effectiveness of SMM. The wild-type BY4743 and the GCN4/gcn4Δ strains were grown and treated as in Figure 3A, except that the medium was SC-met-cys without or with 2 or 4 µg/ml SMM. In SC-met-cys, the GCN4/gcn4Δ strain does not display any phenotype at 2 µg/ml SMM, and a moderate phenotype at 4 µg/ml SMM (compare to Figure 1, top panels). (C) For all phenotypically Met⁺ strains, SMM sensitivity was monitored on SC-met-cys-ile-val medium without or with SMM (6 and 8 µg/ml SMM are shown). Cells were treated as in Figure 3A, except that growth media were SC-met-cys and SC-met-cys-ile-val with SMM. The MON2/mon2Δ strain that had originally shown an SMM-sensitive phenotype is no longer sensitive on SC-met-cys-ile-val with SMM, although the RPL33A/rpl33aΔ, YPL142C/ypl142cΔ, and TAF14/taf14Δ strains remain sensitive to SMM. (D) The diagram indicates the general functional categories for genes identified in the SMM-sensitivity screen as listed in Table 1. The genes from the category “Other” have been omitted.