Rif1 maintains telomeres and mediates DNA repair by encasing DNA ends

• Published in: Nature structural & molecular biology Vol. 24; no. 7; pp. 588 - 595
• Main Authors: Mattarocci, Stefano, Reinert, Julia K, Bunker, Richard D, Fontana, Gabriele A, Shi, Tianlai, Klein, Dominique, Cavadini, Simone, Faty, Mahamadou, Shyian, Maksym, Hafner, Lukas, Shore, David, Thomä, Nicolas H, Rass, Ulrich
• Format: Journal Article
• Language: English
• Published: United States Nature Publishing Group 01.07.2017
• Subjects: Affinity; Baking yeast; Binding Sites; Casing (process); Cellular proteins; Chromosomes; Crystal structure; Crystallography, X-Ray; Deoxyribonucleic acid; DNA; DNA - metabolism; DNA damage; DNA End-Joining Repair; DNA repair; DNA-Binding Proteins - chemistry; DNA-Binding Proteins - metabolism; Genetic aspects; Mammalian cells; Mammals; Models, Molecular; Non-homologous end joining; Properties; Protein Binding; Protein Conformation; Protein Multimerization; Repair; Repressor Proteins - chemistry; Repressor Proteins - metabolism; Saccharomyces cerevisiae; Saccharomyces cerevisiae - enzymology; Saccharomyces cerevisiae Proteins - chemistry; Saccharomyces cerevisiae Proteins - metabolism; Telomerase; Telomere - metabolism; Telomere-Binding Proteins - chemistry; Telomere-Binding Proteins - metabolism; Telomeres; Testing; Yeast
• ISSN: 1545-9993; 1545-9985
• DOI: 10.1038/nsmb.3420

In yeast, Rif1 is part of the telosome, where it inhibits telomerase and checkpoint signaling at chromosome ends. In mammalian cells, Rif1 is not telomeric, but it suppresses DNA end resection at chromosomal breaks, promoting repair by nonhomologous end joining (NHEJ). Here, we describe crystal structures for the uncharacterized and conserved ∼125-kDa N-terminal domain of Rif1 from Saccharomyces cerevisiae (Rif1-NTD), revealing an α-helical fold shaped like a shepherd's crook. We identify a high-affinity DNA-binding site in the Rif1-NTD that fully encases DNA as a head-to-tail dimer. Engagement of the Rif1-NTD with telomeres proved essential for checkpoint control and telomere length regulation. Unexpectedly, Rif1-NTD also promoted NHEJ at DNA breaks in yeast, revealing a conserved role of Rif1 in DNA repair. We propose that tight associations between the Rif1-NTD and DNA gate access of processing factors to DNA ends, enabling Rif1 to mediate diverse telomere maintenance and DNA repair functions.