Structural insights into Pot1-ssDNA, Pot1-Tpz1 and Tpz1-Ccq1 Interactions within fission yeast shelterin complex

PLoS Genet. 2022 Jul 18;18(7):e1010308. doi: 10.1371/journal.pgen.1010308. eCollection 2022 Jul.

Abstract

The conserved shelterin complex caps chromosome ends to protect telomeres and regulate telomere replication. In fission yeast Schizosaccharomyces pombe, shelterin consists of telomeric single- and double-stranded DNA-binding modules Pot1-Tpz1 and Taz1-Rap1 connected by Poz1, and a specific component Ccq1. While individual structures of the two DNA-binding OB folds of Pot1 (Pot1OB1-GGTTAC and Pot1OB2-GGTTACGGT) are available, structural insight into recognition of telomeric repeats with spacers by the complete DNA-binding domain (Pot1DBD) remains an open question. Moreover, structural information about the Tpz1-Ccq1 interaction requires to be revealed for understanding how the specific component Ccq1 of S. pombe shelterin is recruited to telomeres to function as an interacting hub. Here, we report the crystal structures of Pot1DBD-single-stranded-DNA, Pot1372-555-Tpz1185-212 and Tpz1425-470-Ccq1123-439 complexes and propose an integrated model depicting the assembly mechanism of the shelterin complex at telomeres. The structure of Pot1DBD-DNA unveils how Pot1 recognizes S. pombe degenerate telomeric sequences. Our analyses of Tpz1-Ccq1 reveal structural basis for the essential role of the Tpz1-Ccq1 interaction in telomere recruitment of Ccq1 that is required for telomere maintenance and telomeric heterochromatin formation. Overall, our findings provide valuable structural information regarding interactions within fission yeast shelterin complex at 3' ss telomeric overhang.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Carrier Proteins / genetics
  • DNA, Single-Stranded
  • Protein Binding
  • Schizosaccharomyces pombe Proteins* / metabolism
  • Schizosaccharomyces* / genetics
  • Schizosaccharomyces* / metabolism
  • Shelterin Complex
  • Telomerase* / genetics
  • Telomere / genetics
  • Telomere / metabolism
  • Telomere-Binding Proteins / genetics
  • Telomere-Binding Proteins / metabolism

Substances

  • Carrier Proteins
  • Ccq1 protein, S pombe
  • DNA, Single-Stranded
  • Poz1 protein, S pombe
  • Rap1 protein, S pombe
  • Schizosaccharomyces pombe Proteins
  • Shelterin Complex
  • Telomere-Binding Proteins
  • pot1 protein, S pombe
  • taz1 protein, S pombe
  • Telomerase

Grants and funding

This work was supported by grants from the Ministry of Science and Technology of China (2018YFA0107004 to M.L.), the National Natural Science Foundation of China (31930063 to M.L. and 31270787 to Z.Z.) and the Shanghai Municipal Education Commission—Gaofeng Clinical Medicine Grant Support (20181711 to J.W.). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.