Evolving Linear Chromosomes and Telomeres: A C-Strand-Centric View

Recent studies have resulted in deeper understanding of a variety of telomere maintenance mechanisms as well as plausible models of telomere evolution. Often overlookedin the discussion of telomere regulation and evolution is the synthesis of the DNA strand that bears the 5'-end(i.e., the C-strand). Herein, Idescribe ascenario for telomere evolution that more explicitly accounts for the evolution of the C-strand synthesis machinery. In this model, CTC1-STN1-TEN1 (CST), the G-strand-binding complex that regulates primase-Pol alpha-mediated C-strand synthesis, emerges as a pivotal player and evolutionary link. Itself arising from RPA,CST not only coordinates telomere synthesis, but also gives rise to the POT1-TPP1 complex, which became part of shelterin and regulates telomerase in G-strand elongation.