Elucidation of the DNA End-Replication Problem in Saccharomyces cerevisiae

• Published in: Molecular cell Vol. 53; no. 6; pp. 954 - 964
• Main Authors: Soudet, Julien, Jolivet, Pascale, Teixeira, Maria Teresa
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 20.03.2014
• Subjects: Cell Proliferation; Chromosomes, Fungal; DNA - chemistry; DNA - genetics; DNA Replication; DNA, Single-Stranded; Gene Expression Regulation, Fungal; Saccharomyces cerevisiae; Saccharomyces cerevisiae - genetics; Saccharomyces cerevisiae - metabolism; Saccharomyces cerevisiae Proteins - genetics; Saccharomyces cerevisiae Proteins - metabolism; Telomere - chemistry; Telomere Homeostasis; Telomere-Binding Proteins - genetics; Telomere-Binding Proteins - metabolism
• ISSN: 1097-2765; 1097-4164
• DOI: 10.1016/j.molcel.2014.02.030

The model for telomere shortening at each replication cycle is currently incomplete, and the exact contribution of the telomeric 3′ overhang to the shortening rate remains unclear. Here, we demonstrate key steps of the mechanism of telomere replication in Saccharomyces cerevisiae. By following the dynamics of telomeres during replication at near-nucleotide resolution, we find that the leading-strand synthesis generates blunt-end intermediates before being 5′-resected and filled in. Importantly, the shortening rate is set by positioning the last Okazaki fragments at the very ends of the chromosome. Thus, telomeres shorten in direct proportion to the 3′ overhang lengths of 5–10 nucleotides that are present in parental templates. Furthermore, the telomeric protein Cdc13 coordinates leading- and lagging-strand syntheses. Taken together, our data unravel a precise choreography of telomere replication elucidating the DNA end-replication problem and provide a framework to understand the control of the cell proliferation potential. [Display omitted] •Telomeric leading synthesis generates transient blunt-ends and stable G-strands•The leading template C-strand is nucleolytically processed and filled in again•The last RNA primers are positioned at the very end of the chromosomes•Cdc13 couples the syntheses of the telomeric leading and lagging strands Replicative polymerases cannot fully duplicate linear templates, but the underlying mechanism of telomere shortening remains ill defined. Soudet et al. experimentally prove several key steps of end replication in Saccharomyces cerevisiae, demonstrating that telomeres shorten in direct proportion to their 3′ overhang lengths. This mechanism controls the pace of telomere erosion.