Domains in Chromatin Structure

Abstract

The last years have witnessed rapid progress in our understanding of chromatin structure at the nucleosome or beads-on-a-string level (Elgin and Weintraub 1975; Kornberg 1977). Higher orders of chromatin structure have attracted some attention, but here the picture is still far from clear. A coiling of the chromatin filament has been suggested (Finch and Klug 1976; Carpenter et al. 1976); a supercoil or solenoid may be formed with a pitch of 110 Å and a diameter of about 300 Å which correlates with the diameter of the chromatin fibers as observed in electron micrographs (Finch and Klug 1976; see also brief review by Davies 1976), The knobby structure of the 250–300-Å chromatin fibers frequently seen in electron micrographs has recently also been discussed in terms of a globular condensation of nucleosomes (Renz et al. 1977). A further spiralization of the 250–300-Å fibers into a "supersolenoid" of 4000-Å diameter was postulated...