NUCLEOSOMAL ANATOMY - WHERE ARE THE HISTONES

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 r ecent structural advances leading to a new level of understanding of t he nucleosome and chromatin fibre structure. We discuss the problems a nd challenges for existing models of chromatin structure and, in parti cular, consider how linker histones may bind within the nucleosome, to gether with the implications of their association for the structure of the chromatin fibre.