Telomere protection by TPP1/POT1 requires tethering to TIN2

Mol Cell. 2011 Nov 18;44(4):647-59. doi: 10.1016/j.molcel.2011.08.043.

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.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aminopeptidases / genetics
  • Aminopeptidases / metabolism*
  • Animals
  • Ataxia Telangiectasia Mutated Proteins
  • Cell Cycle Proteins / genetics
  • Cell Cycle Proteins / metabolism
  • DNA Damage
  • DNA Repair*
  • DNA, Single-Stranded / chemistry
  • DNA, Single-Stranded / genetics
  • DNA, Single-Stranded / metabolism*
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / metabolism*
  • Dipeptidyl-Peptidases and Tripeptidyl-Peptidases / genetics
  • Dipeptidyl-Peptidases and Tripeptidyl-Peptidases / metabolism*
  • Gene Expression*
  • HeLa Cells
  • Humans
  • Mice
  • Mice, Knockout
  • Protein Binding / genetics
  • Protein-Serine-Threonine Kinases / genetics
  • Protein-Serine-Threonine Kinases / metabolism
  • Recombinant Proteins / genetics
  • Recombinant Proteins / metabolism
  • Serine Proteases / genetics
  • Serine Proteases / metabolism*
  • Signal Transduction / genetics*
  • Telomere / metabolism*
  • Telomere-Binding Proteins / genetics
  • Telomere-Binding Proteins / metabolism*
  • Telomeric Repeat Binding Protein 2 / genetics
  • Telomeric Repeat Binding Protein 2 / metabolism

Substances

  • Cell Cycle Proteins
  • DNA, Single-Stranded
  • DNA-Binding Proteins
  • POT1 protein, mouse
  • Recombinant Proteins
  • Telomere-Binding Proteins
  • Telomeric Repeat Binding Protein 2
  • Tinf2 protein, mouse
  • ATR protein, human
  • Ataxia Telangiectasia Mutated Proteins
  • Protein-Serine-Threonine Kinases
  • Serine Proteases
  • Aminopeptidases
  • Dipeptidyl-Peptidases and Tripeptidyl-Peptidases
  • tripeptidyl-peptidase 1