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. 1999 Mar 15;13(6):698–708. doi: 10.1101/gad.13.6.698

Figure 3.

Figure 3

Deletion of the right boundary leads to a spread of silencing. (A) A schematic depiction of the URA3 insertion at HMR in strains with (ROY687 and ROY853) or without (ROY852 and ROY850) the right boundary element. (B) ROY853 is a sir3Δ strain carrying a URA3 insertion between SGD coordinates 295027 and 295277 (∼1420 bp to the right of HMR-I) with an intact right boundary element. ROY687 is isogenic to ROY853 except that it is Sir+. In strain ROY850 (sir3Δ), the putative right boundary element (between nucleotides 293957 and 294977) was deleted and the URA3 gene with a 1-kb fragment of pUC18 stuffer DNA inserted between nucleotide 295027 and 295277. ROY852 is a Sir+ version of ROY850. All the strains were also transformed with SIR3 on a 2μ-based plasmid (pRO146). The cells were grown in liquid medium and 3 μl of 10-fold serial dilutions was spotted on either supplemented YMD plates lacking tryptophan (−Trp) to select for the plasmid, or supplemented YMD plates lacking tryptophan and uracil (−Trp−Ura), or on supplemented YMD plates lacking tryptophan but containing 1 mg/ml 5-FOA to assay for URA3 expression. Strain numbers are shown in parentheses.