Structural Basis for Shelterin Bridge Assembly
Authors: Clinton Yu
Kyle Roskamp
Jinqiang Liu
Lan Huang
Jin-Kwang Kim
Feng Qiao
Xichan Hu
Elizabeth A Komives
Banumathi Sankaran
Journal: Molecular Cell (2017)
Discipline: MOLECULAR BIOLOGY & GENETICS
Keywords: X-ray crystallography; allosteric structural changes; chromosome; cooperativity; genome instability
Affiliations: Department of Biological Chemistry, School of Medicine, University of California, Irvine, Irvine, CA 92697-1700, USA., Department of Physiology and Biophysics, School of Medicine, University of California, Irvine, Irvine, CA 92697-4560, USA., Department of Chemistry, University of California, Irvine, Irvine, CA 92697-2025, USA., Berkeley Center for Structural Biology, Physical Biosciences Division, Lawrence Berkeley Laboratory, Berkeley, CA 94720, USA., Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA 92093-0378, USA., Department of Biological Chemistry, School of Medicine, University of California, Irvine, Irvine, CA 92697-1700, USA. Electronic address: .

Abstract:  Telomere elongation through telomerase enables chromosome survival during cellular proliferation. The conserved multifunctional shelterin complex associates with telomeres to coordinate multiple telomere activities, including telomere elongation by telomerase. Similar to the human shelterin, fission yeast shelterin is composed of telomeric sequence-specific double- and single-stranded DNA-binding proteins, Taz1 and Pot1, respectively, bridged by Rap1, Poz1, and Tpz1. Here, we report the crystal structure of the fission yeast Tpz1475-508-Poz1-Rap1467-496 complex that provides the structural basis for shelterin bridge assembly. Biochemical analyses reveal that shelterin bridge assembly is a hierarchical process in which Tpz1 binding to Poz1 elicits structural changes in Poz1, allosterically promoting Rap1 binding to Poz1. Perturbation of the cooperative Tpz1-Poz1-Rap1 assembly through mutation of the "conformational trigger" in Poz1 leads to unregulated telomere lengthening. Furthermore, we find that the human shelterin counterparts TPP1-TIN2-TRF2 also assemble hierarchically, indicating cooperativity as a conserved driving force for shelterin assembly. 

Retracted: No

PubPeer comments:
 Figure 2 of this paper shows atomic resolution view of Poz1 dimer binding to peptides derived from Rap1 and Tpz1. However, actual data deposited in PDB (5WE2) does not match the figure shown in the paper, and does not provide detailed structural information for Rap1-Poz1 interaction. Structure of Poz1 N-terminal truncation with Tpz1 (shown in Fig. 5) is also not available in PDB database. Without actual structural data made available to public, claims in this paper cannot be independently verified. , 
 Thank you for your interest in our paper! As shown clearly in Table 1, there were **three** PDB codes (5WE0, 5WE1, and 5WE2****) generated from the work in this paper, as the  actual structural data made available to publicu201d. Also as indicated in Table 1, inquired  Structure of Poz1 N-terminal truncation with Tpz1 (shown in Fig. 5)u201d is deposited as PDB:5WE1. Figure 2 is based on PDB:5WE0. As explained in the section of u2018Crystallization, data collection and structure determinationu2019 in u2018Method detailsu2019 (STAR METHODS). u201cThe native model of Tpz1$475-508$-Poz1-Rap1$470-494$ complex (PDB: 5WE2) was used as a template for molecular replacement. With the high-confidence solution, the final model with clear Rap1 density (for residues 468-484) was further built and refined (PDB: 5WE0). , 
 #2 Thank you for your response, and sorry for overlooking. Indeed, I should have looked 5WE0. I am sorry that I have made you respond to my silly question. Thank you for your beautiful structure, and helping me with my misunderstanding. ,