Premium
Higher‐order structure of long repeat chromatin.
Author(s) -
Widom J.,
Finch J.T.,
Thomas J.O.
Publication year - 1985
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1002/j.1460-2075.1985.tb04064.x
Subject(s) - chromatin , biology , nucleosome , order (exchange) , solenoid , protein filament , physics , dna , genetics , quantum mechanics , finance , economics
The higher‐order structure of chromatin isolated from sea urchin sperm, which has a long nucleosomal DNA repeat length (approximately 240 bp), has been studied by electron microscopy and X‐ray diffraction. Electron micrographs show that this chromatin forms 300 A filaments which are indistinguishable from those of chicken erythrocytes (approximately 212 bp repeat); X‐ray diffraction patterns from partially oriented samples show that the edge‐to‐edge packing of nucleosomes in the direction of the 300 A filament axis, and the radial disposition of nucleosomes around it, are both similar to those of the chicken erythrocyte 300 A filament, which is described by the solenoid model. The invariance of the structure with increased linker DNA length is inconsistent with many other models proposed for the 300 A filament and, furthermore, means that the linker DNA must be bent. The low‐angle X‐ray scattering in the 300‐400 A region both in vitro and in vivo differs from that of chicken erythrocyte chromatin. The nature of the difference suggests that 300 A filaments in sea urchin sperm in vivo are packed so tightly together that electron‐density contrast between individual filaments is lost; this is consistent with electron micrographs of the chromatin in vitro.