Photoaffinity labeling of transcription factors by DNA-templated crosslinkingElectronic supplementary information (ESI) available: Experimental details, characterization data, DNA sequences, and detailed selection procedure. See DOI: 10.1039/c4sc01953a

Characterization of transcription factor-DNA interaction is of high importance in elucidating the molecular mechanisms of gene transcriptions. DNA-based affinity probes were developed to capture and identify transcription factors by covalent crosslinking; however, the requirement of a crosslinker on the affinity probe remains a disadvantage, as the crosslinker itself often interferes with the protein-DNA interactions. We report a dual-probe method able to capture DNA-binding transcription factors with unmodified protein-binding sites in scenarios where conventional probes have failed. We have also shown the method's converse application in selecting specific transcription factor-binding DNA sequences from a probe library and its extension to studying proteins recognizing epigenetic marks. This study may provide a new tool for exploring DNA-binding proteins in biology. A dual-probe system can specifically capture DNA-binding proteins with an unmodified binding site.