Telomere repeat binding factors: keeping the ends in check.
Per definition, a linear chromosome contains two ends, two sites, which by analogy to double-stranded breaks, might be expected to induce cell cycle checkpoints. The fact that cells divide without inducing such checkpoints suggests that telomeres, the natural ends of linear chromosomes, have the ability to suppress checkpoint activation. This suppression takes place at a number of levels. The TTAGGG repeats of human telomeric DNA recruit telomere specific proteins, among them the telomere repeat binding factors TRF1 and TRF2. These proteins, along with their interaction partners, reorganize the linear chromosome end into a t loop, a protected structure, which hides the very end of the chromosome. Here it is discussed how mammalian telomeres differ from DNA breaks, and what methods they use to prevent checkpoint activation.
Karlseder
Jan
J
Regulatory Biology, The Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, CA92037, USA. karlseder@salk.edu <karlseder@salk.edu>
D000818:Animals; D002453:Cell Cycle / Q000235:genetics; D016922:Cellular Senescence / Q000235:genetics; D004249:DNA Damage; D006801:Humans; D019098:Telomerase / Q000235:genetics; D016615:Telomere / Q000235:genetics*; D034501:Telomere-Binding Proteins / Q000235:genetics*; D035321:Telomeric Repeat Binding Protein 1 / Q000235:genetics; D035341:Telomeric Repeat Binding Protein 2 / Q000235:genetics
D034501:Telomere-Binding Proteins; D035321:Telomeric Repeat Binding Protein 1; D035341:Telomeric Repeat Binding Protein 2; D019098:Telomerase