Subtelomeric Elements Influence But Do Not Determine Silencing Levels at Saccharomyces cerevisiae Telomeres

In Saccharomyces cerevisiae, genes placed near telomeres are transcriptionally repressed (telomere position effect, TPE). Although telomeric DNA sequence is the same at all chromosome ends, the subtelomeric elements (STEs) and level of TPE vary from telomere to telomere. We tested whether STEs determine TPE levels. STEs contributed to TPE, as deleting the X element from the VI-R telomere modestly decreased silencing at this telomere. However, STEs were not the major determinant of TPE levels, as inserting the VI-R X element at the truncated VII-L telomere did not increase TPE. These data suggest that the TPE levels of individual telomeres are dependent on some aspect of chromosome context.