Experimental evidence for the influence of molecular crowding on nuclear architecture

J Cell Sci. 2007 May 1;120(Pt 9):1673-80. doi: 10.1242/jcs.03440. Epub 2007 Apr 12.

Abstract

Many compounds in the cell nucleus are structurally organized. To assess the influence of structural organization on nuclear function, we investigated the physical mechanisms of structure formation by using molecular crowding as a parameter for nuclear integrity. Molecular crowding promotes compaction of macromolecular compounds depending on their size and shape without the need for site-specific interactions. HeLa and MCF7 cells were incubated with hypertonic medium to increase crowding of their macromolecular content as a result of the osmotic loss of water. Supplementation of sucrose, sorbitol or NaCl to the growth medium shifted nuclear organization, observed by fluorescence and electron microscopy, towards compaction of chromatin and segregation of other nuclear compounds. With increasing hypertonic load and incubation time, this nuclear re-organization proceeded gradually, irrespective of the substances used, and reversibly relaxed to a regular phenotype upon re-incubation of cells in isotonic growth medium. Gradual and reversible re-organization are major features of controlled de-mixing by molecular crowding. Of fundamental importance for nuclear function, we discuss how macromolecular crowding could account for the stabilization of processes that involve large, macromolecular machines.

MeSH terms

  • Cell Line, Tumor
  • Cell Nucleus / drug effects
  • Cell Nucleus / metabolism*
  • Cell Nucleus / ultrastructure
  • Cell Nucleus Structures / drug effects
  • Cell Nucleus Structures / metabolism
  • Cell Nucleus Structures / ultrastructure
  • Chromatin / drug effects
  • Chromatin / metabolism
  • Chromatin / ultrastructure
  • Dextrans / pharmacology
  • Digitonin / pharmacology
  • HeLa Cells
  • Histones / analysis
  • Humans
  • Hypertonic Solutions / pharmacology
  • Lamin Type A / analysis
  • Microscopy, Confocal
  • Microscopy, Electron, Transmission
  • Microscopy, Fluorescence
  • Nuclear Lamina / drug effects
  • Nuclear Lamina / metabolism
  • Nuclear Lamina / ultrastructure
  • Nuclear Proteins / analysis*
  • Osmotic Pressure
  • Ribonucleoproteins / analysis
  • Serine-Arginine Splicing Factors
  • Sodium Chloride / pharmacology
  • Sorbitol / pharmacology
  • Sucrose / pharmacology

Substances

  • Chromatin
  • Dextrans
  • Histones
  • Hypertonic Solutions
  • LMNA protein, human
  • Lamin Type A
  • Nuclear Proteins
  • Ribonucleoproteins
  • SRSF2 protein, human
  • Serine-Arginine Splicing Factors
  • Sodium Chloride
  • Sorbitol
  • Sucrose
  • Digitonin