1
|
Botos J, Xian W, Smith DF, Smith CL. Progesterone receptor deficient in chromatin binding has an altered cellular state. J Biol Chem 2004; 279:15231-9. [PMID: 14744870 DOI: 10.1074/jbc.m309718200] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Our previous work has shown that the progesterone receptor (PR) can exist in two distinct functional states in mammary adenocarcinoma cells. The differences in function included the ability to activate a promoter in organized chromatin, sensitivity to ligand, and ligand-independent activation. To determine whether these functional differences were because of altered cellular processing, we carried out biochemical analyses of the functionally distinct PRs. Although the majority of PR is localized to the nucleus, biochemical partitioning resulted in a loosely bound (cytosolic) fraction, and a tightly bound (nuclear) fraction. In the absence of progestins, the functionally distinct PRs differed significantly in partitioning between the two fractions. To characterize these fractions further, we analyzed interactions of unliganded PR with chaperones by coimmunoprecipitation. We determined that PR in the cytosolic fraction associated with hsp90 and p23. In contrast, PR in the nuclear fraction consisted of complexes containing hsp90, p23, and FKBP51 as well as PR that was dimerized and highly phosphorylated. Hormone treatment significantly reduced the formation of all PR-chaperone complexes. The hsp90 inhibitor, geldanamycin, similarly blocked transcriptional activity of both functionally distinct receptors. However, the two forms of the PR differed in their ability to associate with the mouse mammary tumor virus promoter in organized chromatin. These findings provide new information about the composition and distribution of mature progesterone receptor complexes in mammary adenocarcinoma cells, and suggest that differences in receptor subcellular distribution have a significant impact on their function. These findings also reveal that transiently expressed steroid receptors may not always be processed like their endogenous counterparts.
Collapse
MESH Headings
- Animals
- Benzoquinones
- Blotting, Western
- Cell Line, Tumor
- Cell Nucleus/metabolism
- Chromatin/chemistry
- Chromatin/metabolism
- Cytosol/metabolism
- DNA/chemistry
- DNA/metabolism
- Dimerization
- Dose-Response Relationship, Drug
- Enzyme Inhibitors/pharmacology
- Fluorescent Antibody Technique, Indirect
- Genes, Viral
- HSP90 Heat-Shock Proteins/metabolism
- Hormones/metabolism
- In Situ Hybridization, Fluorescence
- Intramolecular Oxidoreductases
- Lactams, Macrocyclic
- Ligands
- Luciferases/metabolism
- Mammary Tumor Virus, Mouse/genetics
- Mice
- Microscopy, Fluorescence
- Models, Biological
- Molecular Chaperones/metabolism
- Phosphoproteins/metabolism
- Phosphorylation
- Precipitin Tests
- Promoter Regions, Genetic
- Prostaglandin-E Synthases
- Protein Binding
- Protein Conformation
- Quinones/pharmacology
- Receptors, Progesterone/chemistry
- Receptors, Progesterone/metabolism
- Tacrolimus Binding Proteins/chemistry
- Tacrolimus Binding Proteins/metabolism
- Transcription, Genetic
- Transfection
- beta-Galactosidase/metabolism
Collapse
Affiliation(s)
- Jeannine Botos
- Laboratory of Receptor Biology and Gene Expression, NCI, National Institutes of Health, Bethesda, Maryland 20892-5055, USA.
| | | | | | | |
Collapse
|
2
|
Smith CL, Wolford RG, O'Neill TB, Hager GL. Characterization of transiently and constitutively expressed progesterone receptors: evidence for two functional states. Mol Endocrinol 2000; 14:956-71. [PMID: 10894147 DOI: 10.1210/mend.14.7.0482] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Activated steroid receptors induce chromatin remodeling events in the promoters of some target genes. We previously reported that transiently expressed progesterone receptor (PR) cannot activate mouse mammary tumor virus (MMTV) promoter when it adopts the form of ordered chromatin. However, when expressed continuously, the PR acquires this ability. In this study we explored whether this gain of function occurs through alterations in nucleoprotein structure at the MMTV promoter or through changes in receptor status. We observed no major structural differences at the MMTV promoter in the presence of constitutively expressed PR and found its mechanism of activation to be very similar to that of the glucocorticoid receptor (GR). However, a systematic comparison of the functional behavior of the transiently and constitutively expressed PR elucidated significant differences. The transiently expressed PR is activated in the absence of ligand by cAMP and by components in FBS and has significantly increased sensitivity to progestins. In contrast, the constitutively expressed PR is refractory to activation by cAMP and serum and has normal sensitivity to its ligand. In addition, while the PR is localized to the nucleus in both cases, a significant fraction of the transiently expressed PR is tightly bound to the nucleus even in the absence of ligand, while the majority of constitutively expressed PR is not. These results strongly suggest that the PR undergoes processing in the cell subsequent to its initial expression and that this processing is important for various aspects of its function, including its ability to productively interact with target genes that require chromatin remodeling for activation.
Collapse
Affiliation(s)
- C L Smith
- Laboratory of Receptor Biology and Gene Expression, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA.
| | | | | | | |
Collapse
|
3
|
Sheldon LA, Smith CL, Bodwell JE, Munck AU, Hager GL. A ligand binding domain mutation in the mouse glucocorticoid receptor functionally links chromatin remodeling and transcription initiation. Mol Cell Biol 1999; 19:8146-57. [PMID: 10567540 PMCID: PMC84899 DOI: 10.1128/mcb.19.12.8146] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We utilized the mouse mammary tumor virus (MMTV) long terminal repeat (LTR) in vivo to understand how the interaction of the glucocorticoid receptor (GR) with a nucleosome-assembled promoter allows access of factors required for the transition from a repressed promoter to a derepressed, transcriptionally competent promoter. A mutation (C644G) in the ligand binding domain (LBD) of the mouse GR has provided information regarding the steps required in the derepression/activation process and in the functional significance of the two major transcriptional activation domains, AF1 and AF2. The mutant GR activates transcription from a transiently transfected promoter that has a disordered nucleosomal structure, though significantly less well than the wild-type GR. With an integrated, replicated promoter, which is assembled in an ordered nucleosomal array, the mutant GR does not activate transcription, and it fails to induce chromatin remodeling of the MMTV LTR promoter, as indicated by nuclease accessibility assays. Together, these findings support a two-step model for the transition of a nucleosome-assembled, repressed promoter to its transcriptionally active, derepressed form. In addition, we find that the C-terminal GR mutation is dominant over the transcription activation function of the N-terminal GR activation domain. These findings suggest that the primary activation function of the C-terminal activation domain is different from the function of the N-terminal activation domain and that it is required for derepression of the chromatin-repressed MMTV promoter.
Collapse
Affiliation(s)
- L A Sheldon
- Department of Physiology, Dartmouth Medical School, Lebanon, New Hampshire 03756, USA. Lynn.A.Sheldon.@Dartmouth.edu
| | | | | | | | | |
Collapse
|
4
|
Abstract
Integrin signaling involves oligomerization and a transmembrane conformational change induced by receptor occupancy. Previous work has shown that subsets of focal adhesion-associated proteins are recruited to integrins as a result of clustering, ligand binding, or both. However, it is unclear whether these discrete subsets reflect the differential binding of cytoplasmic proteins to the integrin or whether a single protein or set of proteins binds the integrin and is differentially activated by receptor occupancy or clustering. To address this question, we made mutations of the beta1 integrin cytoplasmic domain in the context of a single subunit chimera and studied their activation of various known integrin-mediated signaling pathways. We show here that the indirect association of the integrin with actin is distinct from its interactions with both preformed focal adhesions and FAK. Therefore, multiple independent signaling pathways exist from the integrin to the focal adhesion, which may reflect the association of independent factors with the integrin beta1 cytoplasmic domain.
Collapse
Affiliation(s)
- F S David
- Department of Pathology, College of Physicians and Surgeons, Columbia University, New York, New York, USA
| | | | | |
Collapse
|
5
|
Lewis E, Rudo T, St John MR, Chu J, Heinze A, Howard B, Engleka K. Endothelial cell DNA transfer and expression using petri dish electroporation and the nonreplicating vaccinia virus/T7 RNA polymerase hybrid system. Gene Ther 1999; 6:1617-25. [PMID: 10490772 DOI: 10.1038/sj.gt.3300977] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The nonreplicating vaccinia virus MVA/T7 RNA polymerase hybrid system was tested with Petri dish electroporation for ectopic gene expression in human umbilical vein endothelial cells (HUVECs). A range of voltages (150-450 V), pulse times (10-40 ms), DNA concentrations (0-20 microg/ml) and infection levels (0-15 multiplicities of infection) were tested for effects on T7 promoter-directed chloramphenicol acetyltransferase (CAT) activity after MVA/T7RP infection. MVA/T7RP-directed expression was transient and at least 10 000-fold in excess of nonviral, cytomegalovirus enhancer-directed expression. Use of a Petri dish electrode with the MVA/T7RP system showed increased viability compared with a cuvette electrode. Overexpression of interleukin-2 alpha subunit (IL2Ralpha) pro- tein followed by anti-IL2Ralpha-directed magnetic immunoaffinity cell sorting allowed isolation of the transfected population. The high fidelity of cellular sorting was shown by segregation of CAT activity in the IL2Ralpha-sorted population after transfection of T7 promoter-directed bicistronic IL2Ralpha/CAT DNA. Expression of a panel of proteins including the fluorophore green fluorescent protein as detected by fluorescence microscopy and p21cip1, p27kip1, pp60c-src, FGF-1, pRb, p107 and pRb2/p130 proteins was also achieved. Thus, use of the nonreplicating vaccinia virus/T7 RNA polymerase expression system with Petri dish electroporation is feasible for certain applications for the manipulation of HUVECs by gene transfer.
Collapse
Affiliation(s)
- E Lewis
- Department of Physiology, Jefferson Medical College, Thomas Jefferson University, Philadelphia, PA 19107-6799, USA
| | | | | | | | | | | | | |
Collapse
|
6
|
Lim CS, Baumann CT, Htun H, Xian W, Irie M, Smith CL, Hager GL. Differential localization and activity of the A- and B-forms of the human progesterone receptor using green fluorescent protein chimeras. Mol Endocrinol 1999; 13:366-75. [PMID: 10076994 DOI: 10.1210/mend.13.3.0247] [Citation(s) in RCA: 100] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Subcellular localization and transcriptional activity of green fluorescent protein-progesterone receptor A and B chimeras (GFP-PRA and GFP-PRB) were examined in living mammalian cells. Both GFP-PRA and B chimeras were found to be similar in transcriptional activity compared with their non-GFP counterparts. GFP-PRA and PRA were both weakly active, while GFP-PRB and PRB gave a 20- to 40-fold induction using a reporter gene containing the full-length mouse mammary tumor virus long-terminal repeat linked to the luciferase gene (pLTRluc). Using fluorescence microscopy, nuclear/cytoplasmic distributions for the unliganded and hormone activated forms of GFP-PRA and GFP-PRB were characterized. The two forms of the receptor were found to have distinct intracellular distributions; GFP-PRA was found to be more nuclear than GFP-PRB in four cell lines examined. The causes for and implications of this differential localization of the A and B forms of the human PR are discussed.
Collapse
Affiliation(s)
- C S Lim
- Laboratory of Receptor Biology and Gene Expression, National Cancer Institute, Bethesda, Maryland 20892-5055, USA
| | | | | | | | | | | | | |
Collapse
|
7
|
Pikaart MJ, Recillas-Targa F, Felsenfeld G. Loss of transcriptional activity of a transgene is accompanied by DNA methylation and histone deacetylation and is prevented by insulators. Genes Dev 1998; 12:2852-62. [PMID: 9744862 PMCID: PMC317165 DOI: 10.1101/gad.12.18.2852] [Citation(s) in RCA: 315] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The constitutive DNase I hypersensitive site at the 5' end of the chicken beta-globin locus marks the boundary of the active chromatin domain in erythroid cells. The DNA sequence containing this site has the properties of an insulator, as shown by its ability in stable transformation experiments to block enhancer-promoter interaction when it lies between the two, but not when it lies outside, and to protect against position effects in Drosophila. We now show that the chicken insulator can protect a stably integrated gene, which is otherwise subject to great variability of expression, from chromatin-mediated repression in cell culture. When the integrated reporter gene is surrounded by insulator elements, stably transformed cell lines display consistent enhancer-dependent expression levels, in accord with the strength of the enhancer. In the absence of insulators, long-term nonselective propagation of cells carrying the integrated reporter gene results in gradual extinction of the reporter's expression, with expression patterns from tandemly repeated inserted genes suggesting that the extinction of adjacent genes is coupled. We show that the uninsulated reporter genes, in addition to becoming transcriptionally inactive, lose several epigenetic hallmarks of active chromatin, including nuclease accessibility, DNA hypomethylation, and histone hyperacetylation during time in culture. Treatment with inhibitors of histone deacetylase or DNA methylation reverses the extinction of the uninsulated genes. Extinction is completely prevented by flanking the reporter construct with insulators. Furthermore, in contrast to the uninsulated reporter genes, chromatin over the insulated genes retains nuclease accessibility and histone hyperacetylation. However, there is no clear correlation between the presence of the insulators and the level of DNA methylation. This leads us to propose a model for the insulator's ability to protect against extinction in the transformed cell lines and to function as a chromatin boundary for the chicken beta-globin locus in normal erythroid cells.
Collapse
Affiliation(s)
- M J Pikaart
- Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA
| | | | | |
Collapse
|
8
|
Bonovich MT, List HJ, Zhang S, Danielsen M, Riegel AT. Identification of glucocorticoid receptor domains necessary for transcriptional activation of the mouse mammary tumor virus promoter integrated in the genome. Exp Cell Res 1998; 239:454-62. [PMID: 9521864 DOI: 10.1006/excr.1997.3920] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
It has previously been determined that the mouse mammary tumor virus (MMTV) promoter when integrated in the genome assumes a defined chromatin structure which is disrupted upon addition of glucocorticoids. In contrast, a transiently introduced MMTV promoter has a random nucleoprotein structure. To reveal glucocorticoid receptor (GR) domains necessary for transcriptional activation of the MMTV promoter we compared the effects of mutations of the GR on transcriptional activation of the stably integrated versus transiently introduced MMTV promoter. For this purpose we generated a GR-negative cell line which has an MMTV promoter/reporter construct integrated in the genome and studied the transcriptional activation of this construct by different GR mutants introduced into the cells. Transcriptional activation of the integrated and transiently introduced promoter was achieved by the wild-type GR or a chimeric receptor in which the MR hormone-binding domain (HBD) replaced the GR HBD. In contrast, we found that deletion of the HBD of the GR or replacement of this region with the equivalent domain of the estrogen receptor produced receptors that were unable to activate the MMTV promoter integrated in the genome although these receptors efficiently activated the transiently introduced MMTV promoter. The HBD was not the sole determinant of MMTV transcriptional activation when integrated in the genome. Chimeric receptors which harbored the MR amino terminal domain or the wild-type MR were also unable to activate the integrated MMTV promoter. Taken together, these data indicate a rigid requirement for sequences in both the GR amino and the carboxy terminal domains for transcriptional activation of a hormone response element in the defined chromatin context of the MMTV promoter.
Collapse
Affiliation(s)
- M T Bonovich
- Department of Biochemistry and Molecular Biology, Georgetown University, Washington, DC 20007, USA
| | | | | | | | | |
Collapse
|
9
|
Ogryzko VV, Wong P, Howard BH. WAF1 retards S-phase progression primarily by inhibition of cyclin-dependent kinases. Mol Cell Biol 1997; 17:4877-82. [PMID: 9234744 PMCID: PMC232340 DOI: 10.1128/mcb.17.8.4877] [Citation(s) in RCA: 149] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
The p21(WAF1/CIP1/sdi1) gene product (WAF1) inhibits DNA replication in vitro (J. Chen, P. Jackson, M. Kirschner, and A. Dutta, Nature 374:386-388, 1995; S. Waga, G. Hannon, D. Beach, and B. Stillman, Nature 369:574-578, 1994), but in vivo studies on the antiproliferative activity of WAF1 have not resolved G1-phase arrest from potential inhibition of S-phase progression. Here, we demonstrate that elevated WAF1 expression can retard replicative DNA synthesis in vivo. The WAF1-mediated inhibitory effect could be antagonized by cyclin A, cyclin E, or the simian virus 40 small-t antigen with no decrease in the levels of WAF1 protein in transfected cells. Proliferating-cell nuclear antigen (PCNA) overexpression was neither necessary nor sufficient to antagonize WAF1 action. Expression of the N-terminal domain of WAF1, responsible for cyclin-dependent kinase (CDK) interaction, had the same effect as full-length WAF1, while the PCNA binding C terminus exhibited modest activity. We conclude that S-phase progression in mammalian cells is dependent on continuing cyclin and CDK activity and that WAF1 affects S phase primarily through cyclin- and CDK-dependent pathways.
Collapse
Affiliation(s)
- V V Ogryzko
- Laboratory of Molecular Growth Regulation, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892-2753, USA
| | | | | |
Collapse
|
10
|
Avantaggiati ML, Ogryzko V, Gardner K, Giordano A, Levine AS, Kelly K. Recruitment of p300/CBP in p53-dependent signal pathways. Cell 1997; 89:1175-84. [PMID: 9215639 DOI: 10.1016/s0092-8674(00)80304-9] [Citation(s) in RCA: 556] [Impact Index Per Article: 20.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The products of the p53 and CBP/p300 genes have been individually implicated in control of cell growth and regulation of transcription. p53 is known to act as a positive and negative regulator of gene expression. Here we show that p53, in both wild-type and mutant conformation, forms a specific protein complex with p300. However, in its wild-type but not mutant conformation, p53 inhibits a promoter containing the DNA-binding sequences for the transcription factor AP1, in a p300-dependent manner. p300 stimulates the transcriptional activity of p53 on p53-regulated promoters, and it enhances the responsiveness to a physiological upstream modulator of p53 function, ionizing radiation. A dominant negative form of p300 prevents transcriptional activation by p53, and it counteracts p53-mediated G1 arrest and apoptosis. The data implicate p300 as an important component of p53-signaling, thus providing new insight into the mechanisms of cellular proliferation.
Collapse
Affiliation(s)
- M L Avantaggiati
- Laboratory of Pathology, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
| | | | | | | | | | | |
Collapse
|
11
|
Savagner P, Yamada KM, Thiery JP. The zinc-finger protein slug causes desmosome dissociation, an initial and necessary step for growth factor-induced epithelial-mesenchymal transition. J Biophys Biochem Cytol 1997; 137:1403-19. [PMID: 9182671 PMCID: PMC2132541 DOI: 10.1083/jcb.137.6.1403] [Citation(s) in RCA: 399] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Epithelial-mesenchymal transition (EMT) is an essential morphogenetic process during embryonic development. It can be induced in vitro by hepatocyte growth factor/scatter factor (HGF/SF), or by FGF-1 in our NBT-II cell model for EMT. We tested for a central role in EMT of a zinc-finger protein called Slug. Slug mRNA and protein levels were increased transiently in FGF-1-treated NBT-II cells. Transient or stable transfection of Slug cDNA in NBT-II cells resulted in a striking disappearance of the desmosomal markers desmoplakin and desmoglein from cell-cell contact areas, mimicking the initial steps of FGF-1 or HGF/SF- induced EMT. Stable transfectant cells expressed Slug protein and were less epithelial, with increased cell spreading and cell-cell separation in subconfluent cultures. Interestingly, NBT-II cells transfected with antisense Slug cDNA were able to resist EMT induction by FGF-1 or even HGF/SF. This antisense effect was suppressed by retransfection with Slug sense cDNA. Our results indicate that Slug induces the first phase of growth factor-induced EMT, including desmosome dissociation, cell spreading, and initiation of cell separation. Moreover, the antisense inhibition experiments suggest that Slug is also necessary for EMT.
Collapse
Affiliation(s)
- P Savagner
- Centre National de la Recherche Scientifique-Institut Curie, 75231 Paris Cedex 05, France
| | | | | |
Collapse
|
12
|
Smith CL, Htun H, Wolford RG, Hager GL. Differential activity of progesterone and glucocorticoid receptors on mouse mammary tumor virus templates differing in chromatin structure. J Biol Chem 1997; 272:14227-35. [PMID: 9162055 DOI: 10.1074/jbc.272.22.14227] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
In vivo, transcription factors interact with promoters having complex nucleoprotein structures. The transiently expressed progesterone receptor (PR) efficiently activates a transfected mouse mammary tumor virus (MMTV) promoter but is a poor activator of the MMTV promoter when it acquires an ordered chromatin structure as an endogenous, replicating gene. We show that the deficiency in PR activity is not due to insufficient expression of either B or A isoforms or competition between the two types of MMTV templates. Rather, this deficiency reflects an inability to induce the chromatin remodeling event that is required for activation of the replicated MMTV template. To determine whether this characteristic is common to transiently expressed steroid receptors or specific to the PR, we examined the activity of transiently expressed glucocorticoid (GR) receptor. Unlike the PR, the transiently expressed GR is an effective activator of both MMTV templates and efficiently induces the necessary chromatin remodeling event at the replicated template. These results indicate that the GR and PR have unique requirements for activation of promoters with ordered chromatin structure. These differences may provide a mechanism for establishing target gene specificity in vivo for steroid receptors that recognize and bind to identical DNA sequences.
Collapse
Affiliation(s)
- C L Smith
- Laboratory of Receptor Biology and Gene Expression, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892-5055, USA
| | | | | | | |
Collapse
|
13
|
Ogryzko VV, Hirai TH, Russanova VR, Barbie DA, Howard BH. Human fibroblast commitment to a senescence-like state in response to histone deacetylase inhibitors is cell cycle dependent. Mol Cell Biol 1996; 16:5210-8. [PMID: 8756678 PMCID: PMC231521 DOI: 10.1128/mcb.16.9.5210] [Citation(s) in RCA: 208] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Human diploid fibroblasts (HDF) complete a limited number of cell divisions before entering a growth arrest state that is termed replicative senescence. Two histone deacetylase inhibitors, sodium butyrate and trichostatin A, dramatically reduce the HDF proliferative life span in a manner that is dependent on one or more cell doublings in the presence of these agents. Cells arrested and subsequently released from histone deacetylase inhibitors display markers of senescence and exhibit a persistent G1 block but remain competent to initiate a round of DNA synthesis in response to simian virus 40 T antigen. Average telomere length in prematurely arrested cells is greater than in senescent cells, reflecting a lower number of population doublings completed by the former. Taken together, these results support the view that one component of HDF senescence mimics a cell cycle-dependent drift in differentiation state and that propagation of HDF in histone deacetylase inhibitors accentuates this component.
Collapse
Affiliation(s)
- V V Ogryzko
- Laboratory of Molecular Growth Regulation, National Institute of Child Health and Human Development, Bethesda, Maryland 20892-2753, USA
| | | | | | | | | |
Collapse
|
14
|
Yang XJ, Ogryzko VV, Nishikawa J, Howard BH, Nakatani Y. A p300/CBP-associated factor that competes with the adenoviral oncoprotein E1A. Nature 1996; 382:319-24. [PMID: 8684459 DOI: 10.1038/382319a0] [Citation(s) in RCA: 1153] [Impact Index Per Article: 41.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The adenoviral oncoprotein E1A induces progression through the cell cycle by binding to the products of the p300/CBP and retinoblastoma gene families. A new cellular p300/CBP-associated factor (P/CAF) having intrinsic histone acetylase activity has been identified that competes with E1A. Exogenous expression of P/CAF in HeLa cells inhibits cell-cycle progression and counteracts the mitogenic activity of E1A. E1A disturbs the normal cellular interaction between p300/CBP and its associated histone acetylase.
Collapse
Affiliation(s)
- X J Yang
- Laboratory of Molecular Growth Regulation, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892-2753, USA
| | | | | | | | | |
Collapse
|
15
|
Htun H, Barsony J, Renyi I, Gould DL, Hager GL. Visualization of glucocorticoid receptor translocation and intranuclear organization in living cells with a green fluorescent protein chimera. Proc Natl Acad Sci U S A 1996; 93:4845-50. [PMID: 8643491 PMCID: PMC39367 DOI: 10.1073/pnas.93.10.4845] [Citation(s) in RCA: 289] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
A highly fluorescent mutant form of the green fluorescent protein (GFP) has been fused to the rat glucocorticoid receptor (GR). When GFP-GR is expressed in living mouse cells, it is competent for normal transactivation of the GR-responsive mouse mammary tumor virus promoter. The unliganded GFP-GR resides in the cytoplasm and translocates to the nucleus in a hormone-dependent manner with ligand specificity similar to that of the native GR receptor. Due to the resistance of the mutant GFP to photobleaching, the translocation process can be studied by time-lapse video microscopy. Confocal laser scanning microscopy showed nuclear accumulation in a discrete series of foci, excluding nucleoli. Complete receptor translocation is induced with RU486 (a ligand with little agonist activity), although concentration into nuclear foci is not observed. This reproducible pattern of transactivation-competent GR reveals a previously undescribed intranuclear architecture of GR target sites.
Collapse
Affiliation(s)
- H Htun
- Laboratory of Molecular Virology, National Cancer Institute, Bethesda, MD 20892-5055, USA
| | | | | | | | | |
Collapse
|
16
|
Tia S, Wang JF, Kotchabhakdi N, Vicini S. Distinct deactivation and desensitization kinetics of recombinant GABAA receptors. Neuropharmacology 1996; 35:1375-82. [PMID: 9014154 DOI: 10.1016/s0028-3908(96)00018-4] [Citation(s) in RCA: 103] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The functional role of the large heterogeneity in GABAA receptor subunit genes and its role in setting the properties of inhibitory synapses in the CNS is poorly understood. A kinetic comparison between currents elicited by ultra-rapid application with a piezoelectric translator of 1 mM GABA to mammalian cells transfected with cDNAs encoding distinct GABAA receptor subunits revealed that the intrinsic deactivation and desensitization properties depend on subunit combination. In particular, receptors containing alpha 6 with beta 2 gamma 2 subunits were endowed with a significantly slower deactivation as compared to those receptors containing alpha 1 with beta 2 gamma 2 subunits. While desensitization produced by prolonged GABA applications on alpha 1 beta 2 gamma 2 receptors was characterized by a rapid exponential decay followed by a slower decay and a steady state response, alpha 6 beta 2 gamma 2 receptors lacked desensitization. Furthermore, GABAA receptors lacking the gamma 2 subunit were characterized by a much larger non-desensitization component and a very rapid deactivation. Lastly, analysis of GABA-activated currents in cells cotransfected with alpha 1 and alpha 6 together with beta 2 gamma 2 subunit revealed unique kinetic properties. Our results suggest that distinct subunit composition confers specific deactivation and desensitization properties that may profoundly affect synaptic decay kinetics and the capability to sustain high frequency synaptic inputs.
Collapse
Affiliation(s)
- S Tia
- Department of Physiology and Biophysics, Georgetown University Medical School, Washington, DC 20007, USA
| | | | | | | |
Collapse
|
17
|
Grant DS, Kinsella JL, Kibbey MC, LaFlamme S, Burbelo PD, Goldstein AL, Kleinman HK. Matrigel induces thymosin beta 4 gene in differentiating endothelial cells. J Cell Sci 1995; 108 ( Pt 12):3685-94. [PMID: 8719875 DOI: 10.1242/jcs.108.12.3685] [Citation(s) in RCA: 127] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We performed differential cDNA hybridization using RNA from endothelial cells cultured for 4 hours on either plastic or basement membrane matrix (Matrigel), and identified early genes induced during the morphological differentiation into capillary-like tubes. The mRNA for one clone, thymosin beta 4, was increased 5-fold. Immunostaining localized thymosin beta 4 in vivo in both growing and mature vessels as well as in other tissues. Endothelial cells transfected with thymosin beta 4 showed an increased rate of attachment and spreading on matrix components, and an accelerated rate of tube formation on Matrigel. An antisense oligo to thymosin beta 4 inhibited tube formation on Matrigel. The results suggest that thymosin beta 4 is induced and likely involved in differentiating endothelial cells. Thymosin beta 4 may play a role in vessel formation in vivo.
Collapse
Affiliation(s)
- D S Grant
- Laboratory of Developmental Biology, National Institute of Dental Research, National Institutes of Health, Bethesda, MD 20892, USA
| | | | | | | | | | | | | |
Collapse
|
18
|
Briesewitz R, Kern A, Marcantonio EE. Assembly and function of integrin receptors is dependent on opposing alpha and beta cytoplasmic domains. Mol Biol Cell 1995; 6:997-1010. [PMID: 7579714 PMCID: PMC301258 DOI: 10.1091/mbc.6.8.997] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
The membrane proximal regions of integrin alpha and beta subunits are highly conserved in evolution. In particular, all integrin alpha subunits share the KXGFFKR sequence at the beginning of their cytoplasmic domains. Previous work has shown that this domain is important in integrin receptor assembly. Using chimeric integrin alpha and beta subunits, we show that the native cytoplasmic domains of both subunits must be present for efficient assembly. Most strikingly, chimeric alpha 1 and beta 1 subunits with reciprocally swapped intracellular domains dimerize selectively into collagen IV receptors expressed at high levels on the surface. However, these receptors, which bind ligand efficiently, are deficient in a variety of post-ligand binding events, including cytoskeletal association and induction of tyrosine phosphorylation. Furthermore, deletion of the distal alpha cytoplasmic domain in the swapped heterodimers leads to ligand-independent focal contact localization, which also occurs in wild-type subunits when the distal cytoplasmic domain is deleted. These results show that proper integrin assembly requires opposed alpha and beta cytoplasmic domains, and this opposition prevents ligand-independent focal contact localization. Our working hypothesis is that these two domains may associate during receptor assembly and provide the mechanism for integrin receptor latency.
Collapse
Affiliation(s)
- R Briesewitz
- Department of Pathology, College of Physicians and Surgeons, Columbia University, New York, New York 10032, USA
| | | | | |
Collapse
|
19
|
Smilenov L, Briesewitz R, Marcantonio EE. Integrin beta 1 cytoplasmic domain dominant negative effects revealed by lysophosphatidic acid treatment. Mol Biol Cell 1994; 5:1215-23. [PMID: 7532472 PMCID: PMC301147 DOI: 10.1091/mbc.5.11.1215] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Integrin receptors localize to focal contact sites and interact with the cytoskeleton via the beta 1 cytoplasmic domain. To study the role of this domain in adhesion, we have expressed in NIH 3T3 cells a cDNA consisting of the interleukin 2 receptor alpha subunit extracellular and transmembrane domains, connected to the integrin beta 1 cytoplasmic domain (IL2R-beta 1). Since the extracellular domain of the chimeric protein has no role in adhesion, this protein could uncouple adhesion from intracellular events. As expected, in a cell line expressing IL2R-beta 1, this chimera was directed to focal contact sites. Unexpectedly, the cells exhibited normal adhesion to fibronectin (FN). However, when a rapid reorganization of the cytoskeleton was induced using lysophosphatidic acid (LPA), IL2R-beta 1 cells detached from FN in contrast to wild-type cells. The detachment in response to LPA could be prevented with cytochalasin D, an inhibitor of actin polymerization. These results imply that a beta 1 cytoplasmic domain, which is uncoupled from adhesion, can compete with the cytoplasmic domain of native integrin beta 1 for cytoskeletal proteins. As a consequence, the IL2R-beta 1 protein acts as a dominant negative effector of adhesion by disrupting the integrin-cytoskeleton connection.
Collapse
Affiliation(s)
- L Smilenov
- Department of Pathology, College of Physicians and Surgeons, Columbia University, New York, New York 10032
| | | | | |
Collapse
|
20
|
LaFlamme SE, Thomas LA, Yamada SS, Yamada KM. Single subunit chimeric integrins as mimics and inhibitors of endogenous integrin functions in receptor localization, cell spreading and migration, and matrix assembly. J Cell Biol 1994; 126:1287-98. [PMID: 8063864 PMCID: PMC2120158 DOI: 10.1083/jcb.126.5.1287] [Citation(s) in RCA: 199] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
The ability of single subunit chimeric receptors containing various integrin beta intracellular domains to mimic and/or inhibit endogenous integrin function was examined. Chimeric receptors consisting of the extracellular and transmembrane domains of the small subunit of the human interleukin-2 receptor connected to either the beta 1, beta 3, beta 3B, or beta 5 intracellular domain were transiently expressed in normal human fibroblasts. When expressed at relatively low levels, the beta 3 and beta 5 chimeras mimicked endogenous ligand-occupied integrins and, like the beta 1 chimera (LaFlamme, S. E., S. K. Akiyama, and K. M. Yamada. 1992. J. Cell Biol. 117:437), concentrated with endogenous integrins in focal adhesions and sites of fibronectin fibril formation. In contrast, the chimeric receptor containing the beta 3B intracellular domain (a beta 3 intracellular domain modified by alternative splicing) was expressed diffusely on the cell surface, indicating that alternative splicing can regulate integrin receptor distribution by an intracellular mechanism. Furthermore, when expressed at higher levels, the beta 1 and beta 3 chimeric receptors functioned as dominant negative mutants and inhibited endogenous integrin function in localization to fibronectin fibrils, fibronectin matrix assembly, cell spreading, and cell migration. The beta 5 chimera was a less effective inhibitor, and the beta 3B chimera and the reporter lacking an intracellular domain did not inhibit endogenous integrin function. Comparison of the relative levels of expression of the transfected beta 1 chimera and the endogenous beta 1 subunit indicated that in 10 to 15 h assays, the beta 1 chimera can inhibit cell spreading when expressed at levels approximately equal to the endogenous beta 1 subunit. Levels of chimeric receptor expression that inhibited cell spreading also inhibited cell migration, whereas lower levels were able to inhibit alpha 5 beta 1 localization to fibrils and matrix assembly. Our results indicate that single subunit chimeric integrins can mimic and/or inhibit endogenous integrin receptor function, presumably by interacting with cytoplasmic components critical for endogenous integrin function. Our results also demonstrate that beta intracellular domains, expressed in this context, display specificity in their abilities to mimic and inhibit endogenous integrin function. Furthermore, the approach that we have used permits the analysis of intracellular domain function in the processes of cell spreading, migration and extracellular matrix assembly independent of effects due to the rest of integrin dimers. This approach should prove valuable in the further analysis of integrin intracellular domain function in these and other integrin-mediated processes requiring the interaction of integrins with cytoplasmic components.
Collapse
Affiliation(s)
- S E LaFlamme
- Laboratory of Developmental Biology, National Institute of Dental Research, National Institutes of Health, Bethesda, Maryland 20892
| | | | | | | |
Collapse
|
21
|
Ogryzko VV, Hirai TH, Shih CE, Howard BH. Dissociation of retinoblastoma gene protein hyperphosphorylation and commitment to enter S phase. J Virol 1994; 68:3724-32. [PMID: 8189510 PMCID: PMC236877 DOI: 10.1128/jvi.68.6.3724-3732.1994] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Mitogenic activities of simian virus 40 large T and small t antigens were studied in serum-deprived human diploid fibroblasts. Wild-type large T and small t cooperated in stimulating DNA synthesis and in inducing hyperphosphorylation of the Rb gene product (pRb). In contrast, a T antigen mutant defective for pRb binding (Rb- T) possessed no detectable mitogenic activity alone and failed to complement small t in stimulating DNA synthesis. Surprisingly, Rb- T and small t cooperated as strongly as wild-type T and small t with respect to pRb hyperphosphorylation. As a consequence, in two closely related conditions (i.e., stimulation by small t plus wild-type T versus small t plus Rb- T), the fraction of pRb in hyperphosphorylated forms dissociated from the fraction of cells in the S phase. These results indicate that pRb hyperphosphorylation is not always tightly coupled with a commitment to initiate DNA replication.
Collapse
Affiliation(s)
- V V Ogryzko
- Laboratory of Molecular Growth Regulation, National Institute of Child Health and Human Development, Bethesda, Maryland 20892
| | | | | | | |
Collapse
|
22
|
Akiyama S, Yamada S, Yamada K, LaFlamme S. Transmembrane signal transduction by integrin cytoplasmic domains expressed in single-subunit chimeras. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)33955-8] [Citation(s) in RCA: 71] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
|
23
|
Abstract
We present evidence for a role for Y-box proteins in both mRNA transcription and translation. We have expressed an oocyte-specific RNA-binding protein (FRGY2) in somatic cells. This protein is normally found together with mRNA in large amounts within the masked maternal mRNA storage particles of Xenopus laevis oocytes. Masked maternal mRNA is believed to be translationally repressed during oogenesis and is stored within ribonucleoprotein storage particles for subsequent use during embryogenesis. Surprisingly, FRGY2 is not only found to direct the accumulation of mRNA from promoters containing binding sites for the protein but also to selectively repress translation of the same mRNA. Thus, the role of FRGY2 in the transcription and storage of maternal mRNA is similar to that of the transcription factor TFIIIA in the transcription and storage of 5S rRNA from the oocyte type 5S rRNA genes.
Collapse
Affiliation(s)
- M Ranjan
- Laboratory of Molecular Embryology, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892
| | | | | |
Collapse
|
24
|
Eisenlohr LC, Yewdell JW, Bennink JR. A transient transfection system for identifying biosynthesized proteins processed and presented to class I MHC restricted T lymphocytes. J Immunol Methods 1992; 154:131-8. [PMID: 1401939 PMCID: PMC7131252 DOI: 10.1016/0022-1759(92)90220-n] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
CD8+ cytotoxic T lymphocytes (CTL) constitute a major portion of immune responses to foreign and self antigens. CTL recognize class I major histocompatibility complex molecules complexed to peptides of 8-10 residues derived from cytosolic proteins. To understand CTL responses to these antigens and to manipulate CTL responses optimally, it is necessary to identify the specific peptides recognized by CTL. The methods currently used for this purpose have significant drawbacks. We describe a plasmid transfection method that results in significant lysis of histocompatible target cells. Influenza virus-specific CTLs specifically lysed target cells that were transfected with plasmids bearing cDNAs encoding full length gene products, fragments containing the region that encodes the CTL epitope, or even a ten residue peptide. This significantly lessens the time and effort required to define genes, and gene segments that contain CTL epitopes.
Collapse
Key Words
- cytotoxic t lymphocyte
- transfection
- vaccinia virus
- antigen presentation
- t7 rna polymerase
- bss/bsa, balanced salt solution with 0.1% bsa
- dna, deoxyribonucleic acid
- ctl, cytotoxic t lymphocyte
- dmem, dulbecco's modified eagle's medium
- dpbs, dulbecco's phosphate-buffered saline
- fbs, fetal bovine serum
- ha, hemagglutinin
- il-2r, interleukin-2 receptor
- imdm, iscove's modified dulbecco's medium
- mhc, major histocompatibility complex
- np, nucleoprotein
- pfu, plaque forming units
- pr8, a/pr/8/34 influenza virus
- vac, vaccinia
Collapse
Affiliation(s)
- L C Eisenlohr
- Laboratory of Viral Diseases, National Institute of Allergy and Infectious Diseases, Bethesda, MD 20892
| | | | | |
Collapse
|
25
|
Abstract
To determine the role of each intracellular domain of the fibronectin receptor in receptor distribution, chimeric receptors were constructed containing the human interleukin-2 receptor (gp55 subunit) as the extracellular and transmembrane domains, in combination with either the alpha 5 or beta 1 intracellular domain of the fibronectin receptor as the cytoplasmic domain. These chimeric receptors were transiently expressed in normal fibroblasts, and their localization on the cell surface was determined by immunofluorescence using antibodies to the human interleukin-2 receptor. The alpha 5 chimera was expressed diffusely on the plasma membrane. The beta 1 chimera, however, colocalized with the endogenous fibronectin receptor at focal contacts of cells spread on fibronectin. On cells spread in the presence of serum, the beta 1 chimera colocalized both with the fibronectin receptor at sites of extracellular fibronectin fibrils and with the vitronectin receptor at focal contacts. The beta 1 intracellular domain alone, therefore, contains sufficient information to target the chimeric receptor to regions of the cell where ligand-occupied integrin receptors are concentrated. The finding that the beta 1 chimeric protein behaves like a ligand-occupied receptor, even though the beta 1 chimera cannot itself bind extracellular ligand, suggests an intracellular difference between occupied and unoccupied receptors, and predicts that the distribution of integrin receptors can be regulated by ligand occupancy. We tested this prediction by providing a soluble cell-binding fragment of fibronectin to cells spread on laminin. Under conditions preventing further ligand adsorption to the substrate, this treatment nevertheless resulted in the relocation of diffuse fibronectin receptors to focal contacts. Similarly, a redistribution of diffuse vitronectin receptors to focal contacts occurred on cells spread on laminin after the addition of the small soluble peptide GRGDS. We conclude that the propensity for receptor redistribution to focal contacts driven by the beta 1 cytoplasmic domain alone is suppressed in heterodimeric unoccupied fibronectin receptors, and that ligand occupancy can release this constraint. This redistribution of integrin receptors after the binding of a soluble substrate molecule may provide a direct means of assembling adhesion sites.
Collapse
Affiliation(s)
- S E LaFlamme
- Laboratory of Developmental Biology, National Institute of Dental Research, National Institutes of Health, Bethesda, Maryland 20892
| | | | | |
Collapse
|