Combinatorial gene regulation by transcription factors

Abstract

Combinatorial gene regulation is encoded in enhancers and promoters in the form of binding sites for transcription factors (TFs), which collaboratively recruit the transcriptional machinery and drive gene expression. Using high-throughput and quantitative technologies developed by our lab and others, we studied TF binding sites in enhancers from numerous different cell types and regulatory systems, shedding light general principles of motif composition and organization in typical cellular regulatory elements. We find extensive synergy between TF binding sites, some with organizational constraints and some with flexible positioning. We demonstrate that different TFs bind at distinct positions within regulatory elements, suggesting a new type of architectural constraint in enhancers. Importantly, our analysis of both TF organization and cooperativity revealed distinctive patterns that separates TFs into potential functional classes. Together, our results suggest a structure of the regulatory code at the level of TF function and generate new hypotheses about regiospecific binding patterns and functions of TF classes within enhancers.