Basic domain of telomere guardian TRF2 reduces D-loop unwinding whereas Rap1 restores it

Nucleic Acids Res. 2017 Dec 1;45(21):12170-12180. doi: 10.1093/nar/gkx812.

Abstract

Telomeric repeat binding factor 2 (TRF2) folds human telomeres into loops to prevent unwanted DNA repair and chromosome end-joining. The N-terminal basic domain of TRF2 (B-domain) protects the telomeric displacement loop (D-loop) from cleavage by endonucleases. Repressor activator protein 1 (Rap1) binds TRF2 and improves telomeric DNA recognition. We found that the B-domain of TRF2 stabilized the D-loop and thus reduced unwinding by BLM and RPA, whereas the formation of the Rap1-TRF2 complex restored DNA unwinding. To understand how the B-domain of TRF2 affects DNA binding and D-loop processing, we analyzed DNA binding of full-length TRF2 and a truncated TRF2 construct lacking the B-domain. We quantified how the B-domain improves TRF2's interaction with DNA via enhanced long-range electrostatic interactions. We developed a structural envelope model of the B-domain bound on DNA. The model revealed that the B-domain is flexible in solution but becomes rigid upon binding to telomeric DNA. We proposed a mechanism for how the B-domain stabilizes the D-loop.

MeSH terms

  • DNA / chemistry*
  • DNA / metabolism
  • Humans
  • Protein Binding
  • Protein Domains
  • Static Electricity
  • Telomere / chemistry*
  • Telomere / metabolism
  • Telomere-Binding Proteins / metabolism*
  • Telomeric Repeat Binding Protein 2 / chemistry*
  • Telomeric Repeat Binding Protein 2 / metabolism*

Substances

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