This domain family is found in eukaryotes, and is typically between 135 and 146 amino acids in length. Rif1 is a protein which interacts with Rap1 to regulate telomere length. Interaction with telomeres limits their length. The N terminal region contains many HEAT- and ARMADILLO- type repeats. These are helical folds which form extended curved proteins or RNA interface surfaces.
This domain is found in N-terminal of the telomere-associated protein,Rif1. In budding yeast, Rif1 is Recruited to telomeres by interaction with the C terminus of RAP1 is recruited to telomeres by interaction with the C terminus of RAP1 and negatively regulates telomere length by preventing telomere elongation or promoting degradation of the telomere ends [PUBMED:1577274, PUBMED:9087429]. In mammals, Rif1 is required for checkpoint mediated arrest of cell cycle progression in response to DNA damage during S-phase (the intra-S-phase checkpoint) [PUBMED:15342490].