PT - JOURNAL ARTICLE AU - Hannon, Colleen E. AU - Blythe, Shelby A. AU - Wieschaus, Eric F. TI - Concentration Dependent Chromatin States Induced by the Bicoid Morphogen Gradient AID - 10.1101/133348 DP - 2017 Jan 01 TA - bioRxiv PG - 133348 4099 - http://biorxiv.org/content/early/2017/05/03/133348.short 4100 - http://biorxiv.org/content/early/2017/05/03/133348.full AB - In Drosophila, graded expression of the maternal transcription factor Bicoid (Bcd) provides positional information to activate target genes at different positions along the anterior-posterior axis. We have measured the genome-wide binding profile of Bcd using ChIP-seq in embryos expressing single, uniform levels of Bcd protein, and grouped Bcd-bound targets into four classes based on occupancy at different concentrations. By measuring the biochemical affinity of target enhancers in these classes in vitro and genome-wide chromatin accessibility by ATAC-seq, we found that the occupancy of target sequences by Bcd is not primarily determined by Bcd binding sites, but by chromatin context. Bcd drives an open chromatin state at a subset its targets. Our data support a model where Bcd influences chromatin structure to gain access to concentration-sensitive targets at high concentrations, while concentration-insensitive targets are found in more accessible chromatin and are bound at low concentrations.