Nucleosome Sub-Structure During Transcription and Replication

We have described (Richards et al. 1977) a model for the sub-structure of the core particle (140 base pairs) of the nucleosome repeat in chromatin, based principally on results from neutron and X-ray scattering, together with data from other physico-chemical studies. Like that proposed by others (Weintraub, Worcel & Alberts 1976), a principal feature of the model is that it consists of two identical halves, each containing a heterotypic histone tetramer, which lie face-to-face about a dyad axis of symmetry. In this brief contribution we give more detail to proposals already mentioned (Richards et al. 1976, 1977) for the manner in which such a particle might linearize to accommodate the action of either the polymerase or replicase enzymes in transcription and replication, respectively