Telomere structure regulates the heritability of repressed subtelomeric chromatin in Saccharomyces cerevisiae

Telomerese, the protein-DNA structures present at the termini of linear chr omosomes, are capable of conferring a reversible repression of Pol II- and Pol III-transcribed genes positioned in adjacent subtelomeric regions. This phenomenon, termed telomeric silencing, is likely to be the consequence of a more global telomere position effect at the level of chromatin structure . To understand the role of telomere structure in this position effect, ive hare developed an assay to distinguish between the heritability of transcr iptionally repressed and derepressed states in yeast. We have previously de monstrated that an elongated telomeric tract leads to hyperrepression of te lomere-adjacent genes. We show here that the predominant effect of elongate d telomeres is to increase the inheritance of the repressed state in cis. I nterestingly, the presence of elongated telomeres overcomes the partial req uirement of yCAF-1 in silencing. We propose that the formation of a specifi c telomeric structure is necessary for the heritability of repressed subtel omeric chromatin.