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Cell Rep. 2017 Jan 3;18(1):41-53. doi: 10.1016/j.celrep.2016.12.005.

Telomere Recognition and Assembly Mechanism of Mammalian Shelterin.

Author information

1
Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA.
2
Laboratory for Cell Biology and Genetics, Rockefeller University, New York, NY 10065, USA.
3
Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
4
Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA. Electronic address: ecg2108@cumc.columbia.edu.
5
Laboratory for Cell Biology and Genetics, Rockefeller University, New York, NY 10065, USA. Electronic address: delange@rockefeller.edu.

Abstract

Shelterin is a six-subunit protein complex that plays crucial roles in telomere length regulation, protection, and maintenance. Although several shelterin subunits have been studied in vitro, the biochemical properties of the fully assembled shelterin complex are not well defined. Here, we characterize shelterin using ensemble biochemical methods, electron microscopy, and single-molecule imaging to determine how shelterin recognizes and assembles onto telomeric repeats. We show that shelterin complexes can exist in solution and primarily locate telomeric DNA through a three-dimensional diffusive search. Shelterin can diffuse along non-telomeric DNA but is impeded by nucleosomes, arguing against extensive one-dimensional diffusion as a viable assembly mechanism. Our work supports a model in which individual shelterin complexes rapidly bind to telomeric repeats as independent functional units, which do not alter the DNA-binding mode of neighboring complexes but, rather, occupy telomeric DNA in a "beads on a string" configuration.

KEYWORDS:

DNA curtains; Rap1; TRF1; TRF2; diffusion; electron microscopy; shelterin; single-molecule imaging; target search; telomere

PMID:
28052260
PMCID:
PMC5225662
DOI:
10.1016/j.celrep.2016.12.005
[Indexed for MEDLINE]
Free PMC Article

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