Cdk1-Dependent Phosphorylation of Cdc13 Coordinates Telomere Elongation during Cell-Cycle Progression

Department of Biochemistry and Biophysics, University of California, San Francisco, Box 2200, San Francisco, CA 94143-2200, USA.
Cell (Impact Factor: 32.24). 02/2009; 136(1):50-61. DOI: 10.1016/j.cell.2008.11.027
Source: PubMed


Elongation of telomeres by telomerase replenishes the loss of terminal telomeric DNA repeats during each cell cycle. In budding yeast, Cdc13 plays an essential role in telomere length homeostasis, partly through its interactions with both the telomerase complex and the competing Stn1-Ten1 complex. Previous studies in yeast have shown that telomere elongation by telomerase is cell cycle dependent, but the mechanism underlying this dependence is unclear. In S. cerevisiae, a single cyclin-dependent kinase Cdk1 (Cdc28) coordinates the serial events required for the cell division cycle, but no Cdk1 substrate has been identified among telomerase and telomere-associated factors. Here we show that Cdk1-dependent phosphorylation of Cdc13 is essential for efficient recruitment of the yeast telomerase complex to telomeres by favoring the interaction of Cdc13 with Est1 rather than the competing Stn1-Ten1 complex. These results provide a direct mechanistic link between coordination of telomere elongation and cell-cycle progression in vivo.

Download full-text


Available from: Tetsuya Matsuguchi, Aug 03, 2015
1 Follower
19 Reads
  • Source
    • "The presence of Tel1 at short telomeres also suggests that phosphorylation of some of the proteins involved may help in the recruitment. Cdc13 is phosphorylated by both Tel1 (and Mec1 in its absence; Tseng et al., 2006) and by CDK1 (Li et al., 2009). In both cases, it has been reported that phosphorylation promotes Est1 binding and thus telomerase recruitment. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Telomeres are nucleoprotein structures that cap the ends of the linear eukaryotic chromosomes and thereby protect their stability and integrity. Telomeres play central roles in maintaining the genome's integrity, distinguishing between the natural chromosomal ends and unwanted double-stranded breaks. In addition, telomeres are replicated by a special reverse transcriptase called telomerase, in a complex mechanism that is coordinated with the genome's replication. Telomeres also play an important role in tethering the chromosomes to the nuclear envelope, thus helping in positioning the chromosomes within the nucleus. The special chromatin configuration of telomeres affects the expression of nearby genes; nonetheless, telomeres are transcribed, creating noncoding RNA molecules that hybridize to the chromosomal ends and seem to play regulatory roles. The yeast Saccharomyces cerevisiae, with its sophisticated genetics and molecular biology, has provided many fundamental concepts in telomere biology, which were later found to be conserved in all organisms. Here, we present an overview of all the aspects of telomere biology investigated in yeast, which continues to provide new insights into this complex and important subject, which has significant medical implications, especially in the fields of aging and cancer.
    FEMS microbiology reviews 03/2014; 38(2):144-71. DOI:10.1111/1574-6976.12054 · 13.24 Impact Factor
  • Source
    • "We paid particular attention to mutations that affected more than one individual. We also generated truncation mutants containing only the N-terminus [N: amino acids (aa) 1–665] or the C-terminus (C: aa 667–1212) and a S517A mutant that abolished a potential phosphorylation site hypothesized to be important for CTC1 function (Li et al., 2009). We chose to analyze these mutations in the murine background to take advantages of our CTC1 À/À mouse embryonic fibroblast (MEFs), which offers the ability to reconstitute mutant proteins while avoiding the confounding effects of endogenous CTC1. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Coats plus is a rare recessive disorder characterized by intracranial calcifications, hematological abnormalities and retinal vascular defects. This disease results from mutations in CTC1, a member of the CTC1-STN1-TEN1 complex critical for telomere replication. Telomeres are specialized DNA/protein structures essential for the maintenance of genome stability. Several Coats plus patients display critically shortened telomeres, suggesting that telomere dysfunction plays an important role in disease pathogenesis. These patients inherit CTC1 mutations in a compound heterozygous manner, with one allele encoding a frameshift mutant and the other a missense mutant. How these mutations impact upon telomere function is unknown. We report here the first biochemical characterization of human CTC1 mutations. We found that all CTC1 frameshift mutations generated truncated or unstable protein products, none of which were able to form a complex with STN1-TEN1 on telomeres, resulting in progressive telomere shortening and formation of fused chromosomes. Missense mutations behaved more like the wild type protein, are able to form the CST complex at telomeres but their expression levels are often repressed by the frameshift mutants. Our results also demonstrate for the first time that CTC1 mutations promote telomere dysfunction by decreasing the stability of STN1 to reduce its ability to interact with DNA Polα, and highlight a previously unknown mechanism to induce telomere dysfunction. This article is protected by copyright. All rights reserved.
    Aging cell 07/2013; 12(6). DOI:10.1111/acel.12139 · 6.34 Impact Factor
  • Source
    • "Cdc13 recruits telomerase to telomeres through binding to Est1, an interaction that is required for telomere extension in vivo [14], [15], [16], [17]. However, the scCST complex negatively regulates telomere length by sequestering the telomeric overhang thus preventing access of telomerase to telomeres [9]. "
    [Show abstract] [Hide abstract]
    ABSTRACT: The identification of the human homologue of the yeast CST in 2009 posed a new challenge in our understanding of the mechanism of telomere capping in higher eukaryotes. The high-resolution structure of the human Stn1-Ten1 (hStn1-Ten1) complex presented here reveals that hStn1 consists of an OB domain and tandem C-terminal wHTH motifs, while hTen1 consists of a single OB fold. Contacts between the OB domains facilitate formation of a complex that is strikingly similar to the replication protein A (RPA) and yeast Stn1-Ten1 (Ten1) complexes. The hStn1-Ten1 complex exhibits non-specific single-stranded DNA activity that is primarily dependent on hStn1. Cells expressing hStn1 mutants defective for dimerization with hTen1 display elongated telomeres and telomere defects associated with telomere uncapping, suggesting that the telomeric function of hCST is hTen1 dependent. Taken together the data presented here show that the structure of the hStn1-Ten1 subcomplex is conserved across species. Cell based assays indicate that hTen1 is critical for the telomeric function of hCST, both in telomere protection and downregulation of telomerase function.
    PLoS ONE 06/2013; 8(6):e66756. DOI:10.1371/journal.pone.0066756 · 3.23 Impact Factor
Show more