CST-Pola/Primase: the second telomere maintenance machine

In this review, Cai and de Lange discuss the role of the CST-Pol & alpha;/Primase complex in telomere length regulation. Providing insight into its structure, evolution, and molecular interactions, they illustrate that CST-Pol & alpha;/Primase not only effectuates fill-in strand synthesis but also controls telomerase to maintain telomere length, while genetic perturbations in its components result in telomeric disorders. It has been known for decades that telomerase extends the 3 & PRIME; end of linear eukaryotic chromosomes and dictates the telomeric repeat sequence based on the template in its RNA. However, telomerase does not mitigate sequence loss at the 5 & PRIME; ends of chromosomes, which results from lagging strand DNA synthesis and nucleolytic processing. Therefore, a second enzyme is needed to keep telomeres intact: DNA polymerase & alpha;/Primase bound to Ctc1-Stn1-Ten1 (CST). CST-Pol & alpha;/Primase maintains telomeres through a fill-in reaction that replenishes the lost sequences at the 5 & PRIME; ends. CST not only serves to maintain telomeres but also determines their length by keeping telomerase from overelongating telomeres. Here we discuss recent data on the evolution, structure, function, and recruitment of mammalian CST-Pol & alpha;/Primase, highlighting the role of this complex and telomere length control in human disease.

Automated summary

In this review, the authors discuss the role of the CST-Polα/Primase complex in telomere length regulation. They highlight that this complex not only functions in strand synthesis but also controls telomerase to maintain telomere length. Additionally, they emphasize the importance of this complex in preventing telomeric disorders by replenishing lost sequences and determining telomere length.