Subtelomeric factors antagonize telomere anchoring and Tel1-independent telomere length regulation

Yeast telomeres are anchored at the nuclear envelope (NE) through redundant pathways that require the telomere-binding factors yKu and Sir4. Significant variation is observed in the efficiency with which different telomeres are anchored, however, suggesting that other forces influence this interaction. Here, we show that subtelomeric elements and the insulator factors that bind them antagonize the association of telomeres with the NE. This is detectable when the redundancy in anchoring pathways is compromised. Remarkably, these same conditions lead to a reduction in steady-state telomere length in the absence of the ATM-kinase homologue Tel1. Both the delocalization of telomeres and reduction in telomere length can be induced by targeting of Tbf1 or Reb1, or the viral transactivator VP16, to a site 23 kb away from the TG repeat. This correlation suggests that telomere anchoring and a Tel1-independent pathway of telomere length regulation are linked, lending a functional significance to the association of yeast telomeres with the NE.