The ends of eukaryotic chromosomes are protected by DNA-protein structures called telomeres. Telomeric DNA is highly conserved, usually consisting of long tracts of a repeating G-rich sequence. @entity14825 telomeric DNA consists of alternating blocks of GGGG and TT sequences (i.e. a G4T2 repeat sequence). We examined the relative importance of the @entity2774 and @entity6244 elements of the repeat sequence in promoting in vitro binding by @entity14825 proteins. We identified single- and, for the first time, double-stranded telomere binding activities from a crude @entity14825 protein extract and tested the binding of these activities to altered telomere repeat sequences. All deletions or substitutions made to the @entity2774 element virtually abolished binding, indicating that four G's are essential for recognition by the binding activity. However, G's alone are not sufficient for efficient binding, as elimination of the @entity6244 element dramatically reduced binding. By contrast, substantial expansion of the @entity6244 element was well tolerated, even though one such change, G4T4, is lethal in vivo. We tested up to a four-fold expansion of the @entity6244 element and found that highly efficient binding was still achieved. These results suggest a minimal recognition sequence for @entity14825 proteins, with the T element providing an important spacer between essential G elements.

Protein binding to expanded telomere repeats in XXXX .

@entity6244 :: ('MESH:D013941', 'Chemical') :: ['thymine'] @entity14825 :: ('5911', 'Species') :: ['T. thermophila', 'Tetrahymena thermophila'] @entity2774 :: ('MESH:D006147', 'Chemical') :: ['guanine']
@entity14825 :: (5911,Species) :: ['Tetrahymena thermophila']
