Nucleosome positioning is proposed to have an essential role in facilitating the regulated transcription of eukaryotic genes. Some transcription factors can bind to DNA when it is appropriately wrapped around the histone core, others cannot bind due to the severe deformation of DNA structure. The staged assembly of nucleosomes and positioning of histone‐DNA contacts away from promoter elements can facilitate the access of transcription factors to DNA. Positioned nucleosomes can also facilitate transcription through providing the appropriate scaffolding to bring regulatory (...) factors bound at dispersed sites into juxtaposition. (shrink)

Nucleosome positioning is proposed to have an essential role in facilitating the regulated transcription of eukaryotic genes. Some transcription factors can bind to DNA when it is appropriately wrapped around the histone core, others cannot bind due to the severe deformation of DNA structure. The staged assembly of nucleosomes and positioning of histone‐DNA contacts away from promoter elements can facilitate the access of transcription factors to DNA. Positioned nucleosomes can also facilitate transcription through providing the appropriate scaffolding to bring regulatory (...) factors bound at dispersed sites into juxtaposition. (shrink)

The recent surge of discoveries concerning the structural organization of nucleosomes, together with genetic evidence of highly specialized roles for the histones in gene regulation, have brought a renewed need for a detailed understanding of nucleosomal anatomy. Here we review recent structural advances leading to a new level of understanding of the nucleosome and chromatin fibre structure. We discuss the problems and challenges for existing models of chromatin structure and, in particular, consider how linker histones may bind within the nucleosome, (...) together with the implications of their association for the structure of the chromatin fibre. (shrink)