PROBER Identifies Proteins Associated with Programable Sequence-Specific DNA in Living Cells

DNA-protein interactions mediate physiologic gene regulation and may be altered by DNA variants linked to polygenic disease. To enhance the speed and signal-to-noise ratio (SNR) of identifying and quantifying proteins that associate with specific DNA sequences in living cells, we developed proximal biotinylation by episomal recruitment (PROBER). PROBER uses high copy episomes to amplify SNR along with proximity proteomics (BioID) to identify the transcription factors (TFs) and additional gene regulators associated with short DNA sequences of interest. PROBER quantified steady-state and inducible association of TFs and corresponding chromatin regulators to target DNA sequences as well as binding quantitative trait loci (bQTLs) due to single nucleotide variants. PROBER identified alterations in regulator associations due to cancer hotspot mutations in the hTERT promoter, indicating these mutations increase promoter association with specific gene activators. PROBER provides an approach to rapidly identify proteins associated with specific DNA sequences and their variants in living cells.