Conserved Telomere Maintenance Component 1 Interacts with STN1 and Maintains Chromosome Ends in Higher Eukaryotes

Orthologs of the yeast telomere protein Stn1 are present in plants, but other components of the Cdc13/Stn1/Ten1 (CST) complex have only been found in fungi. Here we report the identification of conserved telomere maintenance component 1 (CTC1) in plants and vertebrates. CTC1 encodes an similar to 140 kDa telomere-associated protein predicted to contain multiple 013-fold domains. Arabidopsis mutants null for CTC1 display a severe telomere deprotection phenotype accompanied by a rapid onset of developmental defects and sterility. Telomeric and subtelomeric tracts are dramatically eroded, and chromosome ends exhibit increased G overhangs, recombination, and end-to-end fusions. AtCTC11 both physically and genetically interacts with AtSTN1. Depletion of human CTC1 by RNAi triggers a DNA damage response, chromatin bridges, increased G overhangs, and sporadic telomere loss. These data indicate that CTC1 participates in telomere maintenance in diverse species and that a CST-like complex is required for telomere integrity in multicellular organisms.