Figure 7.
A three-state model for telomere length homeostasis. Telomeres are proposed to switch between non-extendible (red, curly end), extendible (green, straight end, middle) and extending states (green straight end associated with telomerase, right). The equilibrium between non-extendible and extendible states is a function of telomere length, while the equilibrium between extendible and extending state is a function of telomerase concentration. The top panel shows a situation where telomerase concentration is limiting, corresponding to the here-analyzed telomerase-positive cell lines. The bottom panel indicates the situation in super-telomerase cells.