Necasová Ivona, Janoušková Eliška, Klumpler Tomáš, Hofr Ctirad
LifeB, Chromatin Molecular Complexes, CEITEC and Functional Genomics and Proteomics, National Centre for Biomolecular Research, Faculty of Science, Masaryk University, Brno CZ-62500, Czech Republic.
Structural Biology of Gene Regulation, CEITEC, Masaryk University, Brno CZ-62500, Czech Republic.
Nucleic Acids Res. 2017 Dec 1;45(21):12170-12180. doi: 10.1093/nar/gkx812.
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.
端粒重复结合因子2（TRF2）将人类端粒折叠成环，以防止不必要的DNA修复和染色体末端连接。TRF2的N端碱性结构域（B结构域）保护端粒置换环（D环）不被核酸内切酶切割。阻遏激活蛋白1（Rap1）与TRF2结合并改善端粒DNA识别。我们发现TRF2的B结构域稳定了D环，从而减少了BLM和RPA引起的解旋，而Rap1-TRF2复合物的形成恢复了DNA解旋。为了了解TRF2的B结构域如何影响DNA结合和D环加工，我们分析了全长TRF2和缺失B结构域的截短TRF2构建体的DNA结合情况。我们量化了B结构域如何通过增强的长程静电相互作用改善TRF2与DNA的相互作用。我们建立了B结构域与DNA结合的结构包络模型。该模型显示，B结构域在溶液中是灵活的，但在与端粒DNA结合时变得刚性。我们提出了B结构域稳定D环的机制。
