Chromatin immunoprecipitation of Rok-myc and Hbs-myc in Bacillus subtilis

The Rok protein of Bacillus subtilis was identified as a negative regulator of competence development. Here we show that Rok binds to extended areas of the B. subtilis genome that are characterized by a high A+T content and are known or believed to have been acquired by horizontal gene transfer, e.g. mobile elements. A deletion of rok results in higher excision of one such element, ICEBs1. The preferential association of Rok with DNA with a high A+T content is also observed in a Gram-negative host, E. coli, and depends on a conserved C-terminal region of the protein. Based on our findings, we propose that Rok is a nucleoid-associated protein that fulfills a function analogous to H-NS, a protein absent from most Gram-positive bacteria. The genome-wide binding profile of the transcription factor Rok and the nucleoid-binding protein HBsu were determined. Three biological replicates were analyzed per strain (one per array). Binding profiles were determined in exponentially growing cells. Enrichment in immunoprecipitated samples versus total genomic DNA were determined.