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. 2014 Jul 24;10(7):e1004436. doi: 10.1371/journal.pgen.1004436

Figure 8. TPE produces TLO expression plasticity.

Figure 8

(A) A cartoon represents URA3 inserted into TLO-adjacent subtelomeres in a head-to-head orientation to test the effect of regulating URA3 expression on TLO expression variability. (B). A diagram depicts the effect on URA3 expression under growth in different conditions and the effect on TLO TAGEN. (C). qRT-PCR measured transcript abundance of TLOα9 and TLOα12 when URA3 was either unselected, selected on media lacking uracil, or selected on 5-FOA. Selection of URA3 expression significantly reduced expression plasticity of the adjacent TLO at either locus but not at the unlinked TLO gene. (D) Subtelomeric loci transition between active and inactive chromatin states. This transcriptional toggling results in a population of cells expressing subtelomeric loci over a wide range. Cells locked into a repressive transcriptional state have lower expression and reduced noise from transcriptional bursting at both the single cell and population level. Conversely, increased transcriptional activity, potentially due to loss of SIR2, increases expression and reduces noise due to increased transcriptional bursting.