Internal organisation of the nucleus: assembly of compartments by macromolecular crowding and the nuclear matrix model.
Many and possibly all macromolecules in the nucleus are segregated into discrete compartments, but the current model that this is achieved by a fibrillar nuclear matrix which structures the nuclear interior and compartments is not consistent with all experimental observations, as reviewed here. New results are presented which suggest that macromolecular crowding forces play a crucial role in the assembly of at least two compartments, nucleoli and PML bodies, and an in vitro system in which crowding assembles macromolecular complexes into structures which resemble nuclear compartments is described. Crowding forces, which are strong in the nucleus due to the high macromolecule concentration (in the range of 100 mg/ml), vastly increase the association constants of intermolecular interactions and can segregate different macromolecules into discrete phases. The model that they play a role in compartmentalisation of the nucleus is generally consistent with the properties of compartments, including their spherical or quasispherical form and their dynamic and mobile nature.
Hancock
Ronald
R
Laval University Cancer Research Centre, Hôtel-Dieu Hospital, 9 rue MacMahon, Quebec, P.Q. G1R 2J6, Canada. ronald.hancock@crhdq.ulaval.ca
D000818:Animals; D002466:Cell Nucleolus / Q000378:metabolism; D002467:Cell Nucleus / Q000187:drug effects / Q000502:physiology* / Q000648:ultrastructure; D004247:DNA / Q000378:metabolism; D006801:Humans; D007038:Hypotonic Solutions / Q000494:pharmacology; D042581:Intranuclear Space / Q000378:metabolism; D046911:Macromolecular Substances / Q000737:chemistry / Q000378:metabolism*; D045170:Matrix Attachment Regions / Q000502:physiology; D008954:Models, Biological; D009363:Neoplasm Proteins / Q000378:metabolism; D015530:Nuclear Matrix / Q000737:chemistry / Q000502:physiology*; D034521:Nuclear Matrix-Associated Proteins / Q000378:metabolism / Q000502:physiology; D009687:Nuclear Proteins / Q000737:chemistry / Q000378:metabolism; D000071156:Promyelocytic Leukemia Protein; D013816:Thermodynamics; D014157:Transcription Factors / Q000378:metabolism; D025521:Tumor Suppressor Proteins
D007038:Hypotonic Solutions; D046911:Macromolecular Substances; D009363:Neoplasm Proteins; D034521:Nuclear Matrix-Associated Proteins; D009687:Nuclear Proteins; D000071156:Promyelocytic Leukemia Protein; D014157:Transcription Factors; D025521:Tumor Suppressor Proteins; C070576:PML protein, human; D004247:DNA