The N-terminus of the protein houses the N-terminal domain of Telomere-associated protein Rif1 N-terminal domain(IPR022031). Budding yeast recruits Rif1 to telomeres through its interaction with the C-terminus of RAP1. It then negatively regulates telomere length by promoting telomere end degradation or impeding telomere elongation. In mammals, Rif1 is needed for DNA damage during S phase to stop the cell cycle and enable the intra-S checkpoint to work.