Human Rap1 modulates TRF2 attraction to telomeric DNA

Nucleic Acids Res. 2015 Mar 11;43(5):2691-700. doi: 10.1093/nar/gkv097. Epub 2015 Feb 11.


More than two decades of genetic research have identified and assigned main biological functions of shelterin proteins that safeguard telomeres. However, a molecular mechanism of how each protein subunit contributes to the protecting function of the whole shelterin complex remains elusive. Human Repressor activator protein 1 (Rap1) forms a multifunctional complex with Telomeric Repeat binding Factor 2 (TRF2). Rap1-TRF2 complex is a critical part of shelterin as it suppresses homology-directed repair in Ku 70/80 heterodimer absence. To understand how Rap1 affects key functions of TRF2, we investigated full-length Rap1 binding to TRF2 and Rap1-TRF2 complex interactions with double-stranded DNA by quantitative biochemical approaches. We observed that Rap1 reduces the overall DNA duplex binding affinity of TRF2 but increases the selectivity of TRF2 to telomeric DNA. Additionally, we observed that Rap1 induces a partial release of TRF2 from DNA duplex. The improved TRF2 selectivity to telomeric DNA is caused by less pronounced electrostatic attractions between TRF2 and DNA in Rap1 presence. Thus, Rap1 prompts more accurate and selective TRF2 recognition of telomeric DNA and TRF2 localization on single/double-strand DNA junctions. These quantitative functional studies contribute to the understanding of the selective recognition of telomeric DNA by the whole shelterin complex.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Binding, Competitive / drug effects
  • DNA / chemistry
  • DNA / genetics
  • DNA / metabolism*
  • Fluorescence Polarization
  • Humans
  • Kinetics
  • Protein Binding / drug effects
  • Sodium Chloride / pharmacology
  • Spectrometry, Fluorescence
  • Static Electricity
  • Surface Plasmon Resonance
  • Telomere / genetics
  • Telomere / metabolism*
  • Telomere-Binding Proteins / chemistry
  • Telomere-Binding Proteins / genetics
  • Telomere-Binding Proteins / metabolism*
  • Telomeric Repeat Binding Protein 2 / chemistry
  • Telomeric Repeat Binding Protein 2 / genetics
  • Telomeric Repeat Binding Protein 2 / metabolism*


  • TERF2 protein, human
  • TERF2IP protein, human
  • Telomere-Binding Proteins
  • Telomeric Repeat Binding Protein 2
  • shelterin, human
  • Sodium Chloride
  • DNA