Diffusion-limited compartmentalization of mammalian cell nuclei assessed by microinjected macromolecules.
In order to investigate the accessibility of the nucleoplasm for macromolecules with different physical properties, we microinjected FITC-conjugated dextrans of different sizes as well as anionic FITC-dextrans and FITC-poly-L-lysine into mammalian cell nuclei. Small dextrans displayed a homogeneous nuclear distribution. With increasing molecular mass (42 to 2500 kDa), FITC-dextrans were progressively excluded from chromatin regions, accumulating in and thereby outlining an apparently extended interchromatin space. Anionic FITC-dextrans (500 kDa) showed complete exclusion from labeled chromatin regions, while the positively charged FITC-poly-L-lysine was to some extent present within the chromatin regions. Moreover, the FITC-poly-L-lysine preferentially localized at the nuclear periphery. We also found a size-dependent exclusion of FITC-dextrans from nucleoli regions, while the FITC-poly-L-lysine accumulated in the nucleoli. Thus, the distinct and restricted nuclear accessibility for macromolecules is dependent on molecule size and electrical charge.
D000818:Animals; D002451:Cell Compartmentation / Q000187:drug effects / Q000502:physiology*; D002466:Cell Nucleolus / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D002467:Cell Nucleus / Q000502:physiology* / Q000648:ultrastructure; D002843:Chromatin / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D003911:Dextrans / Q000378:metabolism; D004058:Diffusion / Q000187:drug effects; D004553:Electric Conductivity; D016650:Fluorescein-5-isothiocyanate / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D046911:Macromolecular Substances; D008322:Mammals / Q000502:physiology*; D008845:Microinjections; D008854:Microscopy, Electron; D008970:Molecular Weight; D011107:Polylysine / Q000378:metabolism
D002843:Chromatin; D003911:Dextrans; D046911:Macromolecular Substances; D011107:Polylysine; D016650:Fluorescein-5-isothiocyanate