Nucleosome positioning and modification: chromatin structures that potentiate transcription.

The role of the nucleosome in the folding of DNA has often been thought of as purely a packaging one. However, the precise folding of regulatory sequences of genes around the histones within positioned nucleosomes is also important in controlling both the access of transcription factors to chromatin and the transcription process itself. This review highlights these functions by using specific examples of an active and regulatory role for positioned nucleosomes.