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TRF1 binds a bipartite telomeric site with extreme spatial flexibility
Author(s) -
Bianchi Alessandro,
Stansel Rachel M.,
Fairall Louise,
Griffith Jack D.,
Rhodes Daniela,
de Lange Titia
Publication year - 1999
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1093/emboj/18.20.5735
Subject(s) - biology , binding site , telomere , dna , helix (gastropod) , dna footprinting , biophysics , dna binding protein , dna binding site , myb , footprinting , microbiology and biotechnology , crystallography , genetics , base sequence , transcription factor , chemistry , promoter , gene , ecology , gene expression , snail
TRF1 is a key player in telomere length regulation. Because length control was proposed to depend on the architecture of telomeres, we studied how TRF1 binds telomeric TTAGGG repeat DNA and alters its conformation. Although the single Myb‐type helix–turn–helix motif of a TRF1 monomer can interact with telomeric DNA, TRF1 predominantly binds as a homodimer. Systematic Evolution of Ligands by Exponential enrichment (SELEX) with dimeric TRF1 revealed a bipartite telomeric recognition site with extreme spatial variability. Optimal sites have two copies of a 5′–YTAGGGTTR–3′ half‐site positioned without constraint on distance or orientation. Analysis of binding affinities and DNase I footprinting showed that both half‐sites are simultaneously contacted by the TRF1 dimer, and electron microscopy revealed looping of the intervening DNA. We propose that a flexible segment in TRF1 allows the two Myb domains of the homodimer to interact independently with variably positioned half‐sites. This unusual DNA binding mode is directly relevant to the proposed architectural role of TRF1.