Est1 is a protein which recruits or activates telomerase at the site of polymerisation [1][2]. Structurally it resembles a TPR-like repeat.

1: Est1p as a cell cycle-regulated activator of telomere-bound telomerase. Taggart AK, Teng SC, Zakian VA; Science. 2002;297:1023-1026. PMID:12169735

2: The Est1 subunit of Saccharomyces cerevisiae telomerase makes multiple contributions to telomere length maintenance. Evans SK, Lundblad V; Genetics. 2002;162:1101-1115. PMID:12454059

3: Telomere maintenance in fission yeast requires an Est1 ortholog. Beernink HT, Miller K, Deshpande A, Bucher P, Cooper JP; Curr Biol. 2003;13:575-580. PMID:12676088