Figure 3.

Repression of hyperresection at telomeres. ATM/CtIP-dependent resection at telomeres is repressed by several independent pathways. On the one hand, the 53BP1 binding partner RIF1 inhibits resection at telomeres that have become dysfunctional such that the ATM kinase pathway has been activated. On the other hand, resection is repressed by TRF2 in shelterin preventing the activation of the ATM kinase and protecting telomeres from moderate resection when 53BP1 is absent (top left and right). In addition, other components in shelterin repress resection so that extensive hyperresection only occurs in the absence of the complete shelterin complex (bottom right).