Аннотация
Special AT-rich binding protein 1 (SATB1) originally was identified
as a protein that bound to the nuclear matrix attachment regions
(MARs) of the immunoglobulin heavy chain intronic enhancer. Subsequently,
SATB1 was shown to repress many genes expressed in the thymus, including
interleukin-2 receptor alpha, c-myc, and those encoded by mouse mammary
tumor virus (MMTV), a glucocorticoid-responsive retrovirus. SATB1
binds to MARs within the MMTV provirus to repress transcription.
To address the role of the nuclear matrix in SATB1-mediated repression,
a series of SATB1 deletion constructs was used to determine protein
localization. Wild-type SATB1 localized to the soluble nuclear, chromatin,
and nuclear matrix fractions. Mutants lacking amino acids 224-278
had a greatly diminished localization to the nuclear matrix, suggesting
the presence of a nuclear matrix targeting sequence (NMTS). Transient
transfection experiments showed that NMTS fusions to green fluorescent
protein or LexA relocalized these proteins to the nuclear matrix.
Difficulties with previous assay systems prompted us to develop retroviral
vectors to assess effects of different SATB1 domains on expression
of MMTV proviruses or integrated reporter genes. SATB1 overexpression
repressed MMTV transcription in the presence and absence of functional
glucocorticoid receptor. Repression was alleviated by deletion of
the NMTS, which did not affect DNA binding, or by deletion of the
MAR-binding domain. Our studies indicate that both nuclear matrix
association and DNA binding are required for optimal SATB1-mediated
repression of the integrated MMTV promoter and may allow insulation
from cellular regulatory elements.
- (genetics);
- alpha
- animal;
- animals
- animals;
- attachment
- binding
- binding;
- c-myc,
- cell
- cells;
- cell_line,_tumor
- cell_nucleus,_metabolism
- chain
- chemistry;
- deletion;
- dimerization
- dimerization;
- dna
- dna,
- dna,_chemistry
- dna_primers,_chemistry
- fibroblasts,
- fibroblasts,_metabolism
- fluorescence;
- fluorescent
- fractions;
- fusion
- gene
- genes,
- genes,_reporter
- genetic;
- genetics;
- gene_deletion
- glands,
- glucocorticoid,
- green
- green_fluorescent_proteins,_metabolism
- humans
- humans;
- interleukin,
- interleukin-2
- interleukin-2_receptor_alpha_subunit
- introns
- introns;
- jurkat
- jurkat_cells
- ligands
- ligands;
- line,
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