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Molecular and Cellular Biology, June 1999, p. 4423-4430, Vol. 19, No. 6
Department of Medicine,
Received 13 January 1999/Returned for modification 24 February
1999/Accepted 2 March 1999
The nuclear body is a cellular structure that appears to be
involved in the pathogenesis of acute promyelocytic leukemia and viral
infection. In addition, the nuclear body is a target of autoantibodies
in patients with the autoimmune disease primary biliary cirrhosis.
Although the precise function of the nuclear body in normal cellular
biology is unknown, this structure may have a role in the regulation of
gene transcription. In a previous investigation, we identified a
leukocyte-specific, gamma interferon (IFN-
0270-7306/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Structural and Functional Heterogeneity of
Nuclear Bodies
)-inducible autoantigen
designated Sp140. The objectives of the present study were to
investigate the cellular location of Sp140 with respect to the
nuclear-body components PML and Sp100 and to examine the potential role
of Sp140 in the regulation of gene transcription. We used
adenovirus-mediated gene transfer to express Sp140 in human cells and
observed that the protein colocalized with PML and Sp100 in resting
cells and associated with structures containing PML during mitosis. In
cells infected with the adenovirus expressing Sp140 and incubated with
IFN-
, the number of PML-Sp100 nuclear bodies per cell increased but immunoreactive Sp140 was not evenly distributed among the nuclear bodies. Sp140 associated with a subset of IFN-
-induced PML-Sp100 nuclear bodies. To examine the potential effect of Sp140 on gene transcription, a plasmid encoding Sp140 fused to the DNA-binding domain
of GAL4 was cotransfected into COS cells with a chloramphenicol acetyltransferase (CAT) reporter gene containing five GAL4-binding sites and a simian virus 40 enhancer region. The GAL4-Sp140 fusion protein increased the expression of the reporter gene. In contrast, Sp100 fused to the GAL4 DNA-binding domain inhibited CAT activity in
transfected mammalian cells. The results of this study demonstrate that
Sp140 associates with a subset of PML-Sp100 nuclear bodies in
IFN-
-treated cells and that Sp140 may activate gene transcription. Taken together, these observations suggest that the nuclear bodies within a cell may be heterogeneous with respect to both composition and function.
*
Corresponding author. Mailing address: Massachusetts
General Hospital-East, CNY-8, 149 13th St., Charlestown, MA 02129. Phone: (617) 726-3780. Fax: (617) 726-5651. E-mail:
bloch{at}helix.mgh.harvard.edu.
Molecular and Cellular Biology, June 1999, p. 4423-4430, Vol. 19, No. 6
0270-7306/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
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