Telomere Position Effect (TPE) is governed by strong repression signals emitted 
by telomeres via the Sir2/3/4 Histone Deacetylase complex. These signals are 
then relayed by weak proto-silencers residing in the subtelomeric core X and Y' 
elements. Subtelomeres also contain Sub-Telomeric Anti-silencing Regions 
(STARs). In this study we have prepared telomeres built of different 
combinations of core X, Y' and STARs and have analyzed them in strains lacking 
Histone-Acetyltransferase genes as well as in cdc6-1 and Δrif1 strains. We show 
that core X and Y' dramatically reduce both positive and negative variations in 
TPE, that are caused by these mutations. We also show that the deletion of 
Histone-Acetyltransferase genes reduce the silencing activity of an ACS 
proto-silencer, but also reduce the anti-silencing activity of a STAR. We 
postulate that core X and Y' act as epigenetic "cushioning" cis-elements.