Transcription factor-mediated chromatin remodelling: mechanisms and models.

The association of DNA with nucleosomes in chromatin severely restricts the access of the regulatory factors that bring about transcription. In vivo active promoters are characterised by altered, almost transparent chromatin structures that allow the interaction of the transcriptional machinery. Recently, enzymatic activities have been discovered that facilitate the binding of transcription factors to chromatin by modifying nucleosomal structures in a process that requires energy. The mechanisms by which chromatin is remodelled may involve nucleosome movements, their transient unfolding, their partial or even complete disassembly. The dynamic properties of chromatin that underlie these structural changes are fundamental to the process of regulated gene expression.