Mitotic chromosomes are chromatin networks without a mechanically contiguous protein scaffold.
Isolated newt (Notophthalmus viridescens) chromosomes were studied by using micromechanical force measurement during nuclease digestion. Micrococcal nuclease and short-recognition-sequence blunt-cutting restriction enzymes first remove the native elastic response of, and then to go on to completely disintegrate, single metaphase newt chromosomes. These experiments rule out the possibility that the mitotic chromosome is based on a mechanically contiguous internal non-DNA (e.g., protein) "scaffold"; instead, the mechanical integrity of the metaphase chromosome is due to chromatin itself. Blunt-cutting restriction enzymes with longer recognition sequences only partially disassemble mitotic chromosomes and indicate that chromatin in metaphase chromosomes is constrained by isolated chromatin-crosslinking elements spaced by approximately 15 kb.
Poirier
Michael G
MG
Department of Physics, University of Illinois, Chicago 60607-7059, USA.
Marko
John F
JF
D000818:Animals; D002843:Chromatin / Q000187:drug effects / Q000648:ultrastructure*; D002875:Chromosomes / Q000187:drug effects / Q000648:ultrastructure*; D004262:DNA Restriction Enzymes / Q000494:pharmacology; D004548:Elasticity; D008677:Metaphase; D008836:Micrococcal Nuclease / Q000494:pharmacology; D008938:Mitosis; D008954:Models, Biological; D009673:Notophthalmus viridescens; D008941:Spindle Apparatus / Q000502:physiology; D013314:Stress, Mechanical
D002843:Chromatin; D004262:DNA Restriction Enzymes; D008836:Micrococcal Nuclease