Figure 1. Model for telomerase recruitment and enrichment at elongating telomere. (A) Example of a Telomerase Recruitment Cluster (T-Rec) in late S phase of the cell cycle (dashed box) (taken from ref. 16). (B) Cell-cycle dependent T-Rec formation on short telomeres depends on the presence of telomerase positive (Tel1, Xrs2, Cdc13) and negative regulators (Rif1/2). (C) Proposed internal architecture of a T-Rec cluster. Successive binding of several telomerase holoenzyme molecules ensures processive elongation of short telomeres in vivo.