Dynamic Nature of CTCF Tandem 11 Zinc Fingers in Multivalent Recognition of DNA As Revealed by NMR Spectroscopy.

The 11 zinc fingers (ZFs) of the transcription factor CTCF play a versatile role in the regulation of gene expression. CTCF binds to numerous genomic sites to form chromatin loops and topologically associated domains and thus mediates the 3D architecture of chromatin. Although CTCF inter-ZF plasticity is essential for the recognition of multiple genomic sites, the dynamic nature of its 11 ZFs remains unknown. We assigned the chemical shifts of the CTCF ZFs 1-11 and solved the solution structures of each ZF. NMR backbone dynamics, residual dipolar couplings, and small-angle X-ray scattering experiments suggest a high inter-ZF plasticity of the free-form ZFs 1-11. As exemplified by two different protocadherin DNA sequences, the titration of DNAs to 15N-labeled CTCF ZFs 1-11 enabled systematic mapping of binding of CTCF ZFs to various chromatin sites. Our work paves the way for illustrating the molecular basis of the versatile DNA recognized by CTCF and has interesting implications for its conformational transition during DNA binding.