Nuclear Matrix Targeting of Steroid Receptors: Specific Signal Sequences and Acceptor Proteins

2000 ◽  
Vol 10 (1) ◽  
pp. 6 ◽  
Author(s):  
Donald B. DeFranco ◽  
Jennifer Guerrero
Keyword(s):  
Nuclear Matrix ◽  
Steroid Receptors ◽  
Signal Sequences ◽  
Specific Signal

scholarly journals ATP-dependent release of glucocorticoid receptors from the nuclear matrix.

1996 ◽  
Vol 16 (5) ◽  
pp. 1989-2001 ◽  
Author(s):  
Y Tang ◽  
D B DeFranco
Keyword(s):  
Nuclear Receptors ◽  
Nuclear Matrix ◽  
Nuclear Export ◽  
Glucocorticoid Receptors ◽  
De Novo ◽  
Steroid Receptors ◽  
Simian Virus 40 ◽  
Atp Depletion ◽  
Nuclear Proteins ◽  
The Matrix

Glucocorticoid receptors (GRs) have the capacity to shuttle between the nuclear and cytoplasmic compartments, sharing that trait with other steroid receptors and unrelated nuclear proteins of diverse function. Although nuclear import of steroid receptors, like that of nearly all other karyophilic proteins examined to date, requires ATP, there appear to be different energetic requirements for export of proteins, including steroid receptors, from nuclei. In an attempt to reveal which steps, if any, in the nuclear export pathway utilized by steroid receptors require ATP, we have used indirect immunofluorescence to visualize GRs within cells subjected to a reversible ATP depletion. Under conditions which lead to >95% depletion of cellular ATP levels within 90 min, GRs remain localized within nuclei and do not efflux into the cytoplasm. Under analogous conditions of ATP depletion, transfected progesterone receptors are also retained within nuclei. Importantly, GRs which accumulate within nuclei of ATP-depleted cells are distinguished from nuclear receptors in metabolically active cells by their resistance to in situ extraction with a hypotonic, detergent-containing buffer. GRs in ATP-depleted cells are not permanently trapped in this nuclear compartment, as nuclear receptors rapidly regain their capacity to be extracted upon restoration of cellular ATP, even in the absence of de novo protein synthesis. More extensive extraction of cells with high salt and detergent, coupled with DNase I digestion, established that a significant fraction of GRs in ATP-depleted cells are associated with an RNA-containing nuclear matrix. Quantitative Western blot (immunoblot) analysis confirmed the dramatic increase in GR binding to the nuclear matrix of ATP-depleted cells, while confocal microscopy revealed that GRs are bound to the matrix throughout all planes of the nucleus. ATP depletion does not lead to wholesale collapse of nuclear proteins onto the matrix, as the interaction of a subpopulation of simian virus 40 large tumor antigen with the nuclear matrix is not quantitatively altered in ATP-depleted Cos-1 cells. Nuclear GRs which are not bound to the nuclear matrix of metabolically active cells (i.e., a DNA-binding domain deletion mutant and a beta-galactosidase chimera possessing the GR nuclear localization signal sequence) are not recruited to the matrix upon depletion of cellular ATP. Thus, it appears that ATP depletion does not expose the GR to nuclear matrix interactions which are not normally encountered in cells but merely alters the dynamics of such interactions. The dynamic association of steroid receptors with the nuclear matrix may provide a mechanism which is utilized by these regulable transcription factors to facilitate their efficient scanning of the genome.

scholarly journals Proteasomal Inhibition Enhances Glucocorticoid Receptor Transactivation and Alters Its Subnuclear Trafficking

2002 ◽  
Vol 22 (12) ◽  
pp. 4113-4123 ◽  
Author(s):  
Bonnie J. Deroo ◽  
Claudia Rentsch ◽  
Sowmini Sampath ◽  
Janel Young ◽  
Donald B. DeFranco ◽  
...  
Keyword(s):  
Glucocorticoid Receptor ◽  
Chromatin Remodeling ◽  
Nuclear Matrix ◽  
Hormone Receptors ◽  
Steroid Receptors ◽  
Proteasome Inhibition ◽  
Factor Loading ◽  
Steroid Hormone Receptors ◽  
Ubiquitin Proteasome ◽  
Subnuclear Trafficking

ABSTRACT The ubiquitin-proteasome pathway regulates the turnover of many transcription factors, including steroid hormone receptors such as the estrogen receptor and progesterone receptor. For these receptors, proteasome inhibition interferes with steroid-mediated transcription. We show here that proteasome inhibition with MG132 results in increased accumulation of the glucocorticoid receptor (GR), confirming that it is likewise a substrate for the ubiquitin-proteasome degradative pathway. Using the mouse mammary tumor virus (MMTV) promoter integrated into tissue culture cells, we found that proteasome inhibition synergistically increases GR-mediated transactivation. This increased activation was observed in a number of cell lines and on various MMTV templates, either as transiently transfected reporters or stably integrated into chromatin. These observations suggest that the increase in GR-mediated transcription due to proteasome inhibition may occur downstream of the initial chromatin remodeling step. In support of this concept, the increase in transcription did not correlate with an increase in chromatin remodeling, as measured by restriction enzyme hypersensitivity, or transcription factor loading, as exemplified by nuclear factor 1. To investigate the relationship between GR turnover, transcription, and subnuclear trafficking, we examined the effect of proteasome inhibition on the mobility of the GR within the nucleus and association of the GR with the nuclear matrix. Blocking GR turnover reduced the mobility of the GR within the nucleus, and this correlated with increased association of the receptor with the nuclear matrix. As a result of proteasome inhibition, GR mobility within the nucleus was reduced while its association with the nuclear matrix was increased. Thus, while altered nuclear mobility of steroid receptors may be a common feature of proteasome inhibition, GR is unique in its enhanced transactivation activity that results when proteasome function is compromised. Proteasomes may therefore impact steroid receptor action at multiple levels and exert distinct effects on individual receptor types.

scholarly journals Interaction of the τ2 Transcriptional Activation Domain of Glucocorticoid Receptor with a Novel Steroid Receptor Coactivator, Hic-5, Which Localizes to Both Focal Adhesions and the Nuclear Matrix

2000 ◽  
Vol 11 (6) ◽  
pp. 2007-2018 ◽  
Author(s):  
Lan Yang ◽  
Jennifer Guerrero ◽  
Heng Hong ◽  
Donald B. DeFranco ◽  
Michael R. Stallcup
Keyword(s):  
Estrogen Receptor ◽  
Glucocorticoid Receptor ◽  
Nuclear Matrix ◽  
Transcriptional Activation ◽  
Steroid Receptors ◽  
Focal Adhesions ◽  
Steroid Receptor ◽  
Terminal Region ◽  
Activation Domain ◽  
Transcriptional Activation Domain

Hic-5 (hydrogen peroxide–inducible clone-5) is a focal adhesion protein that is involved in cellular senescence. In the present study, a yeast two-hybrid screen identified Hic-5 as a protein that interacts with a region of the glucocorticoid receptor that includes a nuclear matrix–targeting signal and the τ2 transcriptional activation domain. In transiently transfected mammalian cells, overexpression of Hic-5 potentiated the activation of reporter genes by all steroid receptors, excluding the estrogen receptor. The activity of the estrogen receptor and the thyroid hormone receptor was stimulated by Hic-5 in the presence but not in the absence of coexpressed coactivator GRIP1. In biochemical fractionations and indirect immunofluorescence assays, a fraction of endogenous Hic-5 in REF-52 cells and transiently expressed Hic-5 in Cos-1 cells was associated with the nuclear matrix. The C-terminal region of Hic-5, which contains seven zinc fingers arranged in four LIM domains, was required for interaction with focal adhesions, the nuclear matrix, steroid receptors, and the τ2 domain of glucocorticoid receptor. The N-terminal region of Hic-5 possesses a transcriptional activation domain and was essential for the coactivator activity of Hic-5. Given the coexisting cytoplasmic and nuclear distributions of Hic-5 and its role in steroid receptor–mediated transcriptional activation, it is proposed that Hic-5 might transmit signals that emanate at cell attachment sites and regulate transcription factors, such as steroid receptors.

Role of molecular chaperones in steroid receptor action

2004 ◽  
Vol 40 ◽  
pp. 41-58 ◽  
Author(s):  
William B Pratt ◽  
Mario D Galigniana ◽  
Yoshihiro Morishima ◽  
Patrick J M Murphy
Keyword(s):  
Transcriptional Activation ◽  
Protein Trafficking ◽  
Steroid Receptors ◽  
Transcriptional Regulatory ◽  
Ubiquitin Proteasome ◽  
Proteasome Pathway ◽  
Receptor Action ◽  
Binding Cleft ◽  
Hsp 90

Unliganded steroid receptors are assembled into heterocomplexes with heat-shock protein (hsp) 90 by a multiprotein chaperone machinery. In addition to binding the receptors at the chaperone site, hsp90 binds cofactors at other sites that are part of the assembly machinery, as well as immunophilins that connect the assembled receptor-hsp90 heterocomplexes to a protein trafficking pathway. The hsp90-/hsp70-based chaperone machinery interacts with the unliganded glucocorticoid receptor to open the steroid-binding cleft to access by a steroid, and the machinery interacts in very dynamic fashion with the liganded, transformed receptor to facilitate its translocation along microtubular highways to the nucleus. In the nucleus, the chaperone machinery interacts with the receptor in transcriptional regulatory complexes after hormone dissociation to release the receptor and terminate transcriptional activation. By forming heterocomplexes with hsp90, the chaperone machinery stabilizes the receptor to degradation by the ubiquitin-proteasome pathway of proteolysis.

984: Variability in the Performance of Nuclear Matrix Protein 22 in the Detection of Bladder Cancer

2006 ◽  
Vol 175 (4S) ◽  
pp. 317-317
Author(s):  
Shahrokh F. Shariat ◽  
Michael Marberger ◽  
Yair Lotan ◽  
Marta Sanchez-Carbayo ◽  
Craig D. Zippe ◽  
...  
Keyword(s):  
Bladder Cancer ◽  
Nuclear Matrix ◽  
Matrix Protein ◽  
Nuclear Matrix Protein

Steroid Receptors as Molecular Targets for Cancer Diagnosis and Therapy

2009 ◽  
Vol 26 (3) ◽  
pp. 207-273 ◽  
Author(s):  
Pramod Mishra ◽  
Arvind Gulbake ◽  
Aviral Jain ◽  
Piush Khare ◽  
Vandana Soni ◽  
...  
Keyword(s):  
Cancer Diagnosis ◽  
Steroid Receptors ◽  
Molecular Targets ◽  
Diagnosis And Therapy ◽  
Cancer Diagnosis And Therapy
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