Abstract
To prevent ATR activation, telomeres deploy the single-stranded DNA binding activity of TPP1/POT1a. POT1a blocks the binding of RPA to telomeres, suggesting that ATR is repressed through RPA exclusion. However, comparison of the DNA binding affinities and abundance of TPP1/POT1a and RPA indicates that TPP1/POT1a by itself is unlikely to exclude RPA. We therefore analyzed the central shelterin protein TIN2, which links TPP1/POT1a (and POT1b) to TRF1 and TRF2 on the double-stranded telomeric DNA. Upon TIN2 deletion, telomeres lost TPP1/POT1a, accumulated RPA, elicited an ATR signal, and showed all other phenotypes of POT1a/b deletion. TIN2 also affected the TRF2-dependent repression of ATM kinase signaling but not to TRF2-mediated inhibition of telomere fusions. Thus, while TIN2 has a minor contribution to the repression of ATM by TRF2, its major role is to stabilize TPP1/POT1a on the ss telomeric DNA, thereby allowing effective exclusion of RPA and repression of ATR signaling.
Copyright © 2011 Elsevier Inc. All rights reserved.
Publication types
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Research Support, N.I.H., Extramural
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Research Support, Non-U.S. Gov't
MeSH terms
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Animals
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Ataxia Telangiectasia Mutated Proteins
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Cell Cycle Proteins / genetics
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Cell Cycle Proteins / metabolism
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DNA Damage
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DNA Repair*
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DNA, Single-Stranded / chemistry
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DNA, Single-Stranded / genetics
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DNA, Single-Stranded / metabolism*
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DNA-Binding Proteins / genetics
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DNA-Binding Proteins / metabolism*
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Gene Expression*
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HeLa Cells
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Humans
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Mice
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Mice, Knockout
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Protein Binding / genetics
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Recombinant Proteins / genetics
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Recombinant Proteins / metabolism
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Shelterin Complex
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Signal Transduction / genetics*
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Telomere / metabolism*
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Telomere-Binding Proteins / genetics
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Telomere-Binding Proteins / metabolism*
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Telomeric Repeat Binding Protein 2 / genetics
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Telomeric Repeat Binding Protein 2 / metabolism
Substances
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ACD protein, human
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Acd protein, mouse
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Cell Cycle Proteins
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DNA, Single-Stranded
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DNA-Binding Proteins
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POT1 protein, mouse
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Recombinant Proteins
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Shelterin Complex
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Telomere-Binding Proteins
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Telomeric Repeat Binding Protein 2
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Tinf2 protein, mouse
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ATR protein, human
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Ataxia Telangiectasia Mutated Proteins