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posted 07. January 2005 19:36
Source: EMBO reports 6, 1, 39–45 (2005)
doi:10.1038/sj.embor.7400314
Published online: 17 December 2004
How the human telomeric proteins TRF1 and TRF2 recognize telomeric DNA: a view from high-resolution crystal structures
Robert Court, Lynda Chapman, Louise Fairall & Daniela Rhodes
MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, UK
*To whom correspondence should be addressed
Daniela Rhodes Tel: +44 1223 248011; Fax: +44 1223 213556; E-mail: rhodes@mrc-lmb.cam.ac.uk
Received 6 September 2004; Accepted 10 November 2004; Published online 17 December 2004.
Abstract
Human telomeres consist of tandem arrays of TTAGGG sequence repeats that are specifically bound by two proteins, TRF1 and TRF2. They bind to DNA ^ as preformed homodimers and have the same architecture in which the DNA-binding domains (Dbds) form independent structural units. Despite these similarities, TRF1 and TRF2 have different functions at telomeres. The X-ray crystal structures of both TRF1- and TRF2-Dbds in complex with telomeric DNA (2.0 and 1.8 Å resolution, respectively) show that they recognize the same TAGGGTT binding site by means of homeodomains, as does the yeast telomeric protein Rap1p. Two of the three G-C ^ base pairs that characterize telomeric repeats are recognized specifically and an unusually large number of water molecules mediate protein−DNA interactions. The binding of the TRF2-Dbd to the DNA double helix shows no distortions that would account for the promotion of t-loops in which TRF2 has been implicated.
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