An expanded codebook of human transcription factor DNA-binding specificity.

The Codebook project determined the sequence specificity of 332 putative and poorly characterized human transcription factors through more than 4,000 independent in vitro and in vivo experiments, yielding motifs for 177 TFs (53%) and about 130 distinct new motifs. The work reveals tens of thousands of previously unknown, conserved and direct TF-binding sites across the human genome, concentrated in promoters and predictive of gene expression. In vitro motifs were strongly enriched in cellular binding sites, addressing controversy over how well motifs reflect in vivo binding.