Keeping fingers crossed: heterochromatin spreading through interdigitation of nucleosome arrays.
Interphase eukaryotic nuclei contain diffuse euchromatin and condensed heterochromatin. Current textbook models suggest that chromatin condensation occurs via accordion-type compaction of nucleosome zigzag chains. Recent studies have revealed several structural aspects that distinguish the highly compact state of condensed heterochromatin. These include an extensive lateral self-association of chromatin fibers, prominent nucleosome linker 'stems', and special protein factors that promote chromatin self-association. Here I review the molecular and structural determinants of chromatin compaction and discuss how heterochromatin spreading may be mediated by lateral self-association of zigzag nucleosome arrays.
Grigoryev
Sergei A
SA
Department of Biochemistry and Molecular Biology, Penn State University College of Medicine, Milton S Hershey Medical Center, Rm. C5757, Hershey, PA 17033, USA. sag17@psu.edu
D000818:Animals; D042002:Chromatin Assembly and Disassembly; D006570:Heterochromatin / Q000502:physiology / Q000648:ultrastructure*; D006801:Humans; D008954:Models, Biological; D009698:Nucleoproteins; D009707:Nucleosomes / Q000648:ultrastructure*
D006570:Heterochromatin; D009698:Nucleoproteins; D009707:Nucleosomes