CST Meets Shelterin to Keep Telomeres in Check

Slides:



Advertisements
Similar presentations
DNA Replicates by a Semiconservative Mechanism Grow cells in 15 N and transfer to 14 N Analyze DNA by equilibrium density gradient centrifugation Presence.
Advertisements

DNA Replicates by a Semiconservative Mechanism Grow cells in 15 N and transfer to 14 N Analyze DNA by equilibrium density gradient centrifugation Presence.
DNA Replication Part 2 Enzymology. Figure The Polymerization Reaction.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Basic Principle: Base Pairing to a Template Strand Since the two strands of.
A Replisome Primase Primosome DNA Polymerase III acts here
DNA Replication-III 28/04/2017.
DNA Double-Strand Break Repair Inhibitors as Cancer Therapeutics
Box H/ACA Small Ribonucleoproteins
The KEOPS Complex: A Rosetta Stone for Telomere Regulation?
Relationship between Genotype and Phenotype
Volume 67, Issue 1, Pages e3 (July 2017)
Volume 49, Issue 1, Pages 3-5 (January 2013)
Volume 50, Issue 4, Pages (May 2013)
Telomere Replication: Mre11 Leads the Way
Volume 52, Issue 6, Pages (December 2013)
Volume 20, Issue 5, Pages (December 2005)
UPF1 Learns to Relax and Unwind
Saving the Ends for Last: The Role of Pol μ in DNA End Joining
James M. Daley, Patrick Sung  Molecular Cell 
DNA Polymerases at the Replication Fork in Eukaryotes
Dynamics under the Telomeric Bridge
Volume 35, Issue 1, Pages 1-10 (July 2009)
RNA Processing and Genome Stability: Cause and Consequence
DNA Double-Strand Break Repair Inhibitors as Cancer Therapeutics
Volume 34, Issue 4, Pages (May 2009)
Eukaryotic Transcription Activation: Right on Target
DNA Mismatch Repair: Dr. Jekyll and Mr. Hyde?
Graeme Hewitt, Viktor I. Korolchuk  Trends in Cell Biology 
Volume 27, Issue 5, Pages (September 2007)
Volume 24, Issue 1, Pages (October 2006)
The Mechanism of E. coli RNA Polymerase Regulation by ppGpp Is Suggested by the Structure of their Complex  Yuhong Zuo, Yeming Wang, Thomas A. Steitz 
Volume 36, Issue 2, Pages (October 2009)
Exposing Secrets of Telomere-Telomerase Encounters
Mechanism of Bidirectional Leading-Strand Synthesis Establishment at Eukaryotic DNA Replication Origins  Valentina Aria, Joseph T.P. Yeeles  Molecular.
UPF1 Learns to Relax and Unwind
Gaston Soria, Sophie E. Polo, Geneviève Almouzni  Molecular Cell 
Paradigms for the Three Rs: DNA Replication, Recombination, and Repair
Volume 28, Issue 6, Pages (December 2007)
PCNA, the Maestro of the Replication Fork
Proteins Kinases: Chromatin-Associated Enzymes?
Karen A. Lewis, Deborah S. Wuttke  Structure 
Andrew N. Blackford, Stephen P. Jackson  Molecular Cell 
Reconsidering DNA Polymerases at the Replication Fork in Eukaryotes
Mark Del Campo, Alan M. Lambowitz  Molecular Cell 
A Histone Code for Chromatin Assembly
Box H/ACA Small Ribonucleoproteins
The Unmasking of Telomerase
Brh2 Promotes a Template-Switching Reaction Enabling Recombinational Bypass of Lesions during DNA Synthesis  Nayef Mazloum, William K. Holloman  Molecular.
Switching and Signaling at the Telomere
The DNA Damage Response: Making It Safe to Play with Knives
Graeme Hewitt, Viktor I. Korolchuk  Trends in Cell Biology 
Volume 29, Issue 6, Pages (March 2008)
The role of the Mre11-Rad50-Xrs2 complex in telomerase- mediated lengthening of Saccharomyces cerevisiae telomeres  Yasumasa Tsukamoto, Andrew K.P Taggart,
Julien Soudet, Pascale Jolivet, Maria Teresa Teixeira  Molecular Cell 
Histone Chaperones: Modulators of Chromatin Marks
Polymerase Switching in DNA Replication
The KEOPS Complex: A Rosetta Stone for Telomere Regulation?
Volume 29, Issue 2, Pages (February 2008)
Apollo—Taking the Lead in Telomere Protection
Polymerases and the Replisome: Machines within Machines
Erin Pennock, Kathleen Buckley, Victoria Lundblad  Cell 
Volume 117, Issue 1, Pages (April 2004)
Are Mouse Telomeres Going to Pot?
Michael J. McIlwraith, Stephen C. West  Molecular Cell 
The DNA Damage Response: Making It Safe to Play with Knives
Huan Chen, Michael Lisby, Lorraine S. Symington  Molecular Cell 
Volume 25, Issue 2, Pages (January 2007)
The Structure of T. aquaticus DNA Polymerase III Is Distinct from Eukaryotic Replicative DNA Polymerases  Scott Bailey, Richard A. Wing, Thomas A. Steitz 
Molecular biology (2) (Foundation Block).
Alessandro Vannini, Patrick Cramer  Molecular Cell 
Presentation transcript:

CST Meets Shelterin to Keep Telomeres in Check Marie-Josèphe Giraud-Panis, M. Teresa Teixeira, Vincent Géli, Eric Gilson  Molecular Cell  Volume 39, Issue 5, Pages 665-676 (September 2010) DOI: 10.1016/j.molcel.2010.08.024 Copyright © 2010 Elsevier Inc. Terms and Conditions

Figure 1 Knowledge before the Discovery of the CST Conservation Before the discovery of the evolutionary conservation of the CST complex, the shelterin mode of capping found in most eukaryotes was opposed to the CST protective functions described in budding yeasts. The relative position of the different complexes on the duplex and single-stranded portions of the telomeric DNA is arbitrary. The gap due to the filling reaction might be transitory, because internal single-stranded stretches at telomeres have not been reported. (A) Saccharomyces cerevisiae telomeres are bound by Rap1-Rif1-Rif2 complex in their double-stranded region and by Cdc13 in their single-stranded region. Cdc13 may interact with Stn1 and Ten1 to form the CST complex. However, the current model establishes that Cdc13-dependent activation of telomerase does not involve Ten1 and Stn1, because these compete with Est1-telomerase complex (blue: telomerase catalytic subunit and Est1 telomerase subunit; dark line: telomerase template RNA) for Cdc13 binding. Telomerase action results in the formation of a long G tail (blue line) that is potentially covered with CST complexes. These, in turn, would stimulate the C-strand synthesis through their interaction with Polα-primase (Pol, red). Subsequent newly formed double-stranded telomeric repeats (with red line indicating the newly synthesized C strand) are then covered by additional Rap1-Rif1-Rif2 complexes that downregulate telomerase. (B) In many other eukaryotes, including humans, the shelterin complex, composed of TRF1, TRF2, RAP1, TIN2, TPP1, and POT1, covers the telomeric chromatin, both the double-stranded part and the single-stranded part. The complex TPP1-POT1 was shown to stimulate telomerase, participating in the increase of the G tail. It is supposed that this G tail is converted into double-stranded telomeric chromatin through the priming by Polα-primase (red as in A), but until recently, no telomeric candidate was convincingly found responsible for coordinating this activity. As in S. cerevisiae, the resulting structure downregulates telomerase from adding additional repeats. (C) Cdc13 was shown to be potentially phosphorylated by Tel1 (S225, S249, S255), Mec1 (S225, S249, S255, S306), and Cdk1 (T308, S336) kinases (Li et al., 2009; Tseng et al., 2006; Tseng et al., 2009; Zhang and Durocher, 2010). In vivo functions of these phosphorylations were reported for S249, S255, S306, and T308. Indeed, phosphorylation of S249 and S255 by Tel1 or Mec1was suggested to be required for telomerase activation (Tseng et al., 2006). Mec1 was shown to have a preponderant role during the establishment of senescence in telomerase-negative cells, but its target or targets in these conditions is or are not known (Abdallah et al., 2009; Khadaroo et al., 2009). Very recently, it was shown that phosphorylation of Cdc13-S306 by Mec1 suppresses Cdc13 accumulation at double-stranded breaks (DSBs) and thereby inhibits telomere healing (Zhang and Durocher, 2010). A C-terminal truncation from position 695 is found in cdc13-5 that leads to overelongated G tails (Chandra et al., 2001). Another allele of CDC13 affecting telomere protection maps within Stn1-binding domain (cdc13-1) (Nugent et al., 1996). Red asterisks mark the single positions mutated in CDC13 alleles that show loss of Pol1 interaction (K50Q, C124R, L129S, S228P, L392P, I523V) (Qi and Zakian, 2000). Molecular Cell 2010 39, 665-676DOI: (10.1016/j.molcel.2010.08.024) Copyright © 2010 Elsevier Inc. Terms and Conditions

Figure 2 A CST-Counting Model for the Regulation of G-Tail Length (A) Model of leading telomere processing. Telomere replication may generate a 3′ overhang and a blunt end in the strands synthesized by the lagging or the leading strand synthesis machinery, respectively. MRX is recruited to the leading strand telomere (Faure et al., 2010), initiating the processing of this telomere that leads to 3′ to 5′ resection. Sae2, Sgs1, Dna 2, and Exo1 helicase or nuclease activities are involved in this process in an order of events very similar to the processing of DSBs (Bonetti et al., 2009; Mimitou and Symington, 2008). The telomere nucleolytic processing is limited by Rap1 and Ku (Bonetti et al., 2010) and by CST (Frank et al., 2006; Vodenicharov and Wellinger, 2006). (B) Asymmetric versus symmetric mode of telomere replication model. Semiconservative DNA replication machinery is asymmetric, with distinct machineries replicating the continuous and discontinuous strands. At telomeres, further 5′ to 3′ resection at leading strand telomere, and eventual telomerase-dependent telomere elongation, generates a long G tail. This latter may bind CST, which, in turn, activates the Polα-primase. Subsequently, in this model, the long, single-stranded DNA formed at leading telomeres is filled by discontinuous synthesis of the C strand. (C) CST may block the access to Exo1 and/or other nuclease and helicase activities. (D) CST might activate Polα-primase-dependent C-strand synthesis, compensating overhang production activities. (E) As the G tail increases, it may be bound by an increasing number of CST complexes that, in turn, prevent its further extension and/or actively compensate by C-strand resynthesis. This dynamic equilibrium determined by the CST complex would provide a finely tuned control of the G-tail length. Molecular Cell 2010 39, 665-676DOI: (10.1016/j.molcel.2010.08.024) Copyright © 2010 Elsevier Inc. Terms and Conditions

Figure 3 Structural Similarities between RPA and CST (A) Schematic view of human RPA subunits (RPA70, RPA32, and RPA14) and CST proteins (ScCdc13, Stn1, and Ten1). Light orange and light purple domains correspond to putative OB folds and wHTH domains, respectively. (B) Detail of the X-ray structure of RPA70 AB OB folds; only the B domain is shown (PDB 1FGU) (Bochkareva et al., 2001). (C) Detail of the solution structure of Cdc13 OB fold bound to ssDNA; only the protein is shown (PDB 1S40) (Mitton-Fry et al., 2004). (D) X-ray structure of the heterodimer RPA32D-RPA14 (PDB 1QUQ) (Bochkarev et al., 1999). Conserved secondary structures between RPA32C and Stn1 proteins are shown in cyan and red for conservation between RPA14 and Ten1 proteins. These regions were drawn according to Sun et al. (2009). (E) X-ray structure of the heterodimer between the N-terminal domain of SpStn1 and SpTen1 (PDB 3KF6) (Sun et al., 2009). (F) X-ray structure of the heterodimer between the N-terminal domain of CtStn1 and CtTen1 (PDB 3KF8) (Sun et al., 2009). (G) Detail of the solution structure of the complex between the C-terminal wHTH domain of human RPA32 (RPA32D) and UNG2; only RPA32D is shown (PDB 1DPU) (Mer et al., 2000). (H) X-ray structure of the C-terminal wHTH domains of ScStn1 (PDB 3K10) (Gelinas et al., 2009). These figures were built from Protein Data Bank data using the PyMOL software. Molecular Cell 2010 39, 665-676DOI: (10.1016/j.molcel.2010.08.024) Copyright © 2010 Elsevier Inc. Terms and Conditions

Figure 4 A Shelterin-CST Alliance to Keep the G Tail in Check The double-stranded region of telomeres is covered with shelterin complexes that inhibit the activation of ATM. The inhibition of ATR may be achieved by both limiting the length of the G tail through a CST-dependent stimulation of C-strand synthesis and covering it with single-stranded telomeric proteins such as POT1 and CST itself. Molecular Cell 2010 39, 665-676DOI: (10.1016/j.molcel.2010.08.024) Copyright © 2010 Elsevier Inc. Terms and Conditions