DNA at the entry-exit of the nucleosome observed by cryoelectron microscopy.
Whereas the DNA path inside the nucleosome is well established, it is essentially unknown in the "entry-exit" region, a missing piece in our understanding of the chromatin fiber's folding. The three-dimensional structure of "linker" DNA was investigated here on single nucleosomes reconstituted without H1 on a 256-bp DNA fragment. Cryoelectron microscopy and three-dimensional reconstruction of the DNA axis reveal these nucleosomes as 1.61 +/- 0.15 left-handed superhelical turn particles whose DNA arms bend away from the core particle, thus preventing the occurrence of a crossing in the entry-exit region.
Furrer
P
P
Laboratoire d'Analyse Ultrastructurale, Section de Biologie, Université de Lausanne, Dorigny, Switzerland.
Bednar
J
J
Dubochet
J
J
Hamiche
A
A
Prunell
A
A
D000818:Animals; D002843:Chromatin / Q000737:chemistry; D003196:Computer Graphics; D018360:Crystallography, X-Ray; D004247:DNA / Q000737:chemistry* / Q000648:ultrastructure; D004591:Electrophoresis, Polyacrylamide Gel; D005615:Freezing; D006657:Histones / Q000737:chemistry; D007091:Image Processing, Computer-Assisted; D008854:Microscopy, Electron; D008958:Models, Molecular; D009690:Nucleic Acid Conformation; D009707:Nucleosomes / Q000737:chemistry*
D002843:Chromatin; D006657:Histones; D009707:Nucleosomes; D004247:DNA