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.

1: Human Rif1, ortholog of a yeast telomeric protein, is regulated by ATM and 53BP1 and functions in the S-phase checkpoint. Silverman J, Takai H, Buonomo SB, Eisenhaber F, de Lange T; Genes Dev. 2004;18:2108-2119. PMID:15342490