Chromatin fibers are left-handed double helices with diameter and mass per unit length that depend on linker length

• Published in: Biophysical Journal [BIOPHYS. J.]. Vol. 44, no. 1. 1986 Vol. 44; no. 1
• Main Authors: Williams, S P, Athey, B D, Muglia, L J, Schappe, R S, Gough, AH, Langmore, J P
• Format: Conference Proceeding
• Language: English
• Published: 01-01-1986
• Subjects: Necturus; Thyone
• ISSN: 0006-3495

Four classes models have been proposed for the internal structure of eukaryotic chromosome fibers - the solenoid, twisted-ribbon, crossed-linker, and superbead models. The authors have collected electron image and x-ray scattering data from nuclei, and isolated chromatin fibers of seven different tissues to distinguish between these models. The fiber diameters are related to the linker lengths by the equation: D(N) = 19.3 + 0.23 N, where D(N) is the external diameter (nm) and N is the linker length (base pairs). The number of nucleosomes per unit length of the fibers is also related to linker length. Detailed studies were done on the highly regular chromatin from erythrocytes of Necturus (mud puppy) and sperm of Thyone (sea cucumber). The data do not support the solenoid, twisted-ribbon, or supranucleosomal particle models. The data do support two crossed linker models having left-handed double-helical symmetry and conserved nucleosome interactions.