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

Figure 4.

Figure 4

Boundary elements block the spread of silenced chromatin. (A) (Top) A schematic representation of boundary element insertions at the EcoNI site of the MATa2 gene at nucleotide 292140 of wild-type HMR. (B) ROY113 (MATα HMRΔ, nucleotide 288980–295350) was transformed with a 10-kb fragment of wild-type HMR carrying either (1) a 1 kb stuffer fragment of the TRP1 gene, or (2) a 1.6-kb fragment of the putative left boundary element (from nucleotide 289256 to 290846), or (3) a 1-kb fragment of the putative right boundary element (from nucleotide 293695 to 294686) at the EcoNI site of the MATa2 gene (at nucleotide 292140). Expression of the MATa1 gene was monitored by patch-mating assays using JRY19 as the mating tester lawn. All matings were performed under conditions that constantly selected for the plasmid. (B) (Top) A schematic representation of boundary element insertions at the EcoNI site of the MATa2 gene at nucleotide 292140 of HMRΔI. (Bottom) ROY113 (MATα HMRΔ) transformants carrying an 8-kb fragment of HMRΔI with the same set of putative boundary insertions as described in A (bottom) were used to monitor expression of MATa1.