High Mobility Group 1 Protein Is Not Stably Associated with the Chromosomes of Somatic Cells

High mobility group 1 (HMG1) protein is an abundant and conserved component of vertebrate nuclei and has been proposed to play a structural role in chromatin organization, possibly similar to that of histone H1. However, a high abundance of HMG1 had also been reported in the cytoplasm and on the sur...

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Bibliographic Details
Published in:The Journal of cell biology 1997-04, Vol.137 (1), p.19-26
Main Authors: Falciola, Luca, Spada, Fabio, Calogero, Sabina, Längst, Gernot, Voit, Renate, Grummt, Ingrid, Bianchi, Marco E.
Format: Article
Language:English
Subjects:
3T3 Cells - chemistry
3T3 Cells - physiology
Amino Acid Sequence
Animals
Antibodies
Antibodies, Monoclonal
Cell lines
Cell Nucleus - chemistry
Cell Nucleus - genetics
Cell Nucleus - immunology
Cells
Cellular biology
Chickens
Chromatin
Chromosomes
Chromosomes - chemistry
Chromosomes - physiology
DNA
Epitopes - analysis
Epitopes - immunology
Escherichia coli - genetics
Fibroblasts
Genes
High Mobility Group Proteins - genetics
High Mobility Group Proteins - immunology
High Mobility Group Proteins - metabolism
Histones
Histones - analysis
Histones - immunology
Histones - metabolism
Interphase
Interphase - physiology
Mice
Mice, Inbred BALB C
Molecular Sequence Data
Nucleosomes
Nucleosomes - metabolism
Proteins
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Summary:High mobility group 1 (HMG1) protein is an abundant and conserved component of vertebrate nuclei and has been proposed to play a structural role in chromatin organization, possibly similar to that of histone H1. However, a high abundance of HMG1 had also been reported in the cytoplasm and on the surface of mammalian cells. We conclusively show that HMG1 is a nuclear protein, since several different anti-HMG1 antibodies stain the nucleoplasm of cultured cells, and epitope-tagged HMG1 is localized in the nucleus only. The protein is excluded from nucleoli and is not associated to specific nuclear structures but rather appears to be uniformly distributed. HMG1 can bind in vitro to reconstituted core nucleosomes but is not stably associated to chromatin in live cells. At metaphase, HMG1 is detached from condensed chromosomes, contrary to histone H1. During interphase, HMG1 readily diffuses out of nuclei after permeabilization of the nuclear membranes with detergents, whereas histone H1 remains associated to chromatin. These properties exclude a shared function for HMG1 and H1 in differentiated cells, in spite of their similar biochemical properties. HMG1 may be stably associated only to a very minor population of nucleosomes or may interact transiently with nucleosomes during dynamic processes of chromatin remodeling.
ISSN:0021-9525
1540-8140
DOI:10.1083/jcb.137.1.19