Inhibition of the 26S proteasome blocks progesterone receptor-dependent transcription through failed recruitment of RNA polymerase II

Dennis, Andrew P.; Lonard, David M.; Nawaz, Zafar; O’Malley, Bert W.

doi:10.1016/j.jsbmb.2004.11.009

Cited by 56 publications

(47 citation statements)

References 40 publications

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“…In accord with previous studies [14,28], we observed that MPA inhibits PR expression in human breast cancer cells; in the present study MPA inhibited expression of PR in BT-474 xenograft tumors in both apigenin-treated and untreated animals. As described previously, exogenous progestins stimulate proteasomal degradation of PR [29], which is associated with functional PR activity.…”

Section: Discussionsupporting

confidence: 93%

“…To rule out the possibility that treatment with apigenin leads to a complete loss of PR we assessed PR levels in tumor sections. Our findings concur with previous reports [14,28], which show that the number of PR-positive cells is significantly lower in mice treated with MPA or both MPA and apigenin (p<0.05), compared with controls (Fig. 5).…”

Section: Immunohistochemical Analysis For Prsupporting

confidence: 94%

“…5). Partial loss of PR has been associated with functional PR activity [28,29] and in this case suggests that apigenin, by virtue of its inability to totally eradicate PR, does not inhibit tumor growth in this model by completely eliminating PR.…”

Section: Immunohistochemical Analysis For Prmentioning

confidence: 66%

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Apigenin Induces Apoptosis and Blocks Growth of Medroxyprogesterone Acetate-Dependent BT-474 Xenograft Tumors

et al. 2012

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Recent clinical and epidemiological evidence shows that hormone replacement therapy (HRT) containing both estrogen and progestin increases the risk of primary and metastatic breast cancer in post-menopausal women while HRT containing only estrogen does not. We and others previously showed that progestins promote the growth of human breast cancer cells in vitro and in vivo. In this study, we sought to determine whether apigenin, a low molecular weight anticarcinogenic flavonoid, inhibits the growth of aggressive Her2/neu-positive BT-474 xenograft tumors in nude mice exposed to medroxyprogesterone acetate (MPA), the most commonly used progestin in the USA. Our data clearly show that apigenin (50 mg/kg) inhibits progression and development of these xenograft tumors by inducing apoptosis, inhibiting cell proliferation, and reducing expression of Her2/neu. Moreover, apigenin reduced levels of vascular endothelial growth factor (VEGF) without altering blood vessel density, indicating that continued expression of VEGF may be required to promote tumor cell survival and maintain blood flow. While previous studies showed that MPA induces receptor activator of nuclear factor kappa-B ligand (RANKL) expression in rodent mammary gland, MPA reduced levels of RANKL in human tumor xenografts. RANKL levels remained suppressed in the presence of apigenin. Exposure of BT-474 cells to MPA in vitro also resulted in lower levels of RANKL; an effect that was independent of progesterone receptors since it occurred both in the presence and absence of the antiprogestin RU-486. In contrast to our in vivo observations, apigenin protected against MPA-dependent RANKL loss in vitro, suggesting that MPA and apigenin modulate RANKL levels differently in breast cancer cells in vivo and in vitro. These preclinical findings suggest that apigenin has potential as an agent for the treatment of progestin-dependent breast disease.

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Section: Discussionsupporting

confidence: 93%

Section: Immunohistochemical Analysis For Prsupporting

confidence: 94%

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Apigenin Induces Apoptosis and Blocks Growth of Medroxyprogesterone Acetate-Dependent BT-474 Xenograft Tumors

et al. 2012

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“…On the contrary, in some cases, the activity of the proteasome is required for transcription. Transcriptional activation by the progesterone receptor is inhibited by drugs that inhibit the proteasome (Dennis et al, 2005); ubiquitylation of Gcn4, and the proteolytic function of the proteasome are necessary for transcription mediated by this factor (Lipford et al, 2005); Gal4 ubiquitylation and destruction are required for activation by Gal4. Defects in the ubiquitylation and stability of this transcriptional activator leads to inappropriate phosphorylation of RNA pol II and pre-mRNA processing (Muratani et al, 2005).…”

Section: Discussionmentioning

confidence: 99%

Posttranslational Regulation of NF-YA Modulates NF-Y Transcriptional Activity

Manni¹,

Caretti

Artuso³

et al. 2008

MBoC

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Here we show that the levels of NF-YA protein are regulated posttranslationally by ubiquitylation and acetylation. A NF-YA protein carrying four mutated lysines in the C-terminal domain is more stable than the wild-type form, indicating that these lysines are ubiquitylated Two of the lysines are acetylated in vitro by p300, suggesting a competition between ubiquitylation and acetylation of overlapping residues. Interestingly, overexpression of a degradation-resistant NF-YA protein leads to sustained expression of mitotic cyclin complexes and increased cell proliferation, indicating that a tight regulation of NF-YA levels contributes to regulate NF-Y activity. INTRODUCTIONThe CCAAT-binding transcription factor NF-Y is a heteromeric protein composed of three subunits, NF-YA, -YB, and -YC, all necessary for CCAAT binding (Mantovani, 1999). The NF-Y complex supports the basal transcription of a class of regulatory genes responsible for cell cycle progression, among which are mitotic cyclin complexes (Zwicker et al., 1995a,b;Bolognese et al., 1999;Farina et al., 1999;Korner et al., 2001;Gurtner et al., 2003Gurtner et al., , 2008Di Agostino et al., 2006). Knock-out mice clearly demonstrates that NF-Y dependent transcription is essential during early mouse development (Bhattacharya et al., 2003). The NF-Y function in proliferation is also demonstrated by the inhibition of DNA binding by endogenous NF-Y, resulting in retardation of fibroblast growth, which is brought about by overexpression of a dominant negative mutant of the NF-YA subunit (Hu and Maity, 2000). The differential expression of NF-YA, altering NF-Y CCAAT-binding activity, has been observed in several cell lines and tissues both during cell cycle progression and under specific conditions. NF-YA expression is modulated during the cell cycle, being high in G1, further increasing in S, and then decreasing in the G2/M phase (Bolognese et al., 1999). Reduction of NF-YA expression has been reported in IMR-90 fibroblasts after serum deprivation (Chang et al., 1994) and in human monocytes (Marziali et al., 1997). The NF-YA protein is not expressed in terminally differentiated C2C12 muscle cells and adult skeletal muscle tissues (Farina et al., 1999;Gurtner et al., 2003Gurtner et al., , 2008. These observations show that levels of NF-YA dictate the function of the NF-Y complex. Interestingly, control of NF-YA accumulation is posttranscriptional, because NF-YA mRNA is relatively constant in growing and differentiated cells (Bolognese et al., 1999;Farina et al., 1999). Yet, the mechanisms regulating the stability of the NF-YA protein remain unknown.The covalent addition of ubiquitin, a 76-amino acid protein highly conserved among eukaryotes, is an increasingly common posttranslation modification that controls both the expression and the activity of numerous proteins in the eukaryotic cell (Hershko and Ciechanover, 1998;Ciechanover et al., 2000). The ubiquitin-proteasome pathway is composed of the ubiquitin-conjugating system and the 26S proteasome; the latter contain...

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“…Stabilize the Receptor-Ligand-dependent transactivation of nuclear receptors is often associated with proteasome-mediated degradation of the receptor (33,34). Ligand-induced proteolysis serves as a common mechanism to terminate transcriptional activity of the ligand-activated receptors (33,34).…”

Section: Ppar␦ Ligandsmentioning

confidence: 99%

Block of Nuclear Receptor Ubiquitination

Genini

Catapano

2007

Journal of Biological Chemistry

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Peroxisome proliferator-activated receptor ␦ (PPAR␦) is a ligand-activated transcription factor involved in many physiological and pathological processes. PPAR␦ is a promising therapeutic target for metabolic, chronic inflammatory, and neurodegenerative disorders. However, limited information is available about the mechanisms that control the activity of this nuclear receptor. Here, we examined the role of the ubiquitinproteasome system in PPAR␦ turnover. The receptor was ubiquitinated and subject to rapid degradation by the 26 S proteasome. Unlike most nuclear receptors that are degraded upon ligand binding, PPAR␦ ligands inhibited the ubiquitination of the receptor, thereby preventing its degradation. Ligand binding was required for inhibition of the ubiquitination since disruption of the ligand binding domain abolished the effect. Sitedirected mutagenesis showed that the DNA binding domain was also required, indicating that ligands preferentially stabilized the DNA-bound receptor. In contrast, the activation function-2 domain and co-repressor binding site were not involved in ligand-induced stabilization. Block of ubiquitination by ligands may be an essential step to avoid rapid degradation of a receptor, like PPAR␦, with a very short half-life and sustain its transcriptional activity once it is engaged in transcriptional activation complexes.Peroxisome proliferator-activated receptors (PPARs) 2 belong to the superfamily of nuclear hormone receptors and act as ligand-activated transcription factors (1). PPARs are activated by a diverse group of lipophilic compounds, including long-chain fatty acids, prostaglandins, and leukotrienes (2). PPARs form heterodimers with the retinoic X receptor and bind DNA in correspondence to specific PPAR response elements (PPRE) located in the promoter of target genes (1). Unliganded receptors maintain the promoter in a repressive or inactive state (3). Ligand binding induces a conformational remodeling of the receptor, resulting in the release of co-repressor molecules and recruitment of co-activators necessary for transcriptional activation (3). The PPAR subfamily includes three isotypes, named ␣, ␦ (or ␤), and ␥, that share extensive structural homology (1). Although all three isotypes act as lipid sensors and are involved in various aspects of lipid metabolism, they have distinct tissue distribution, ligand specificity, and functions (2, 4). PPAR␣ is involved in fatty acid metabolism, and high affinity ligands of this receptor, like fenofibrate and bezafibrate, are effective hypolipidemic drugs (5). PPAR␥ prevalently controls lipid and glucose metabolism, and PPAR␥ agonists, like rosiglitazone and pioglitazone, are widely used antidiabetic drugs (6). PPAR␦, which is the less studied of the three isotypes, has been implicated in wound healing, inflammatory responses, and embryo implantation in addition to lipid metabolism (4, 7). PPAR␦ is a potential therapeutic target for diseases such as atherosclerosis and other inflammatory, metabolic, and neurodegenerative disorders (7)...

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Inhibition of the 26S proteasome blocks progesterone receptor-dependent transcription through failed recruitment of RNA polymerase II

Cited by 56 publications

References 40 publications

Apigenin Induces Apoptosis and Blocks Growth of Medroxyprogesterone Acetate-Dependent BT-474 Xenograft Tumors

Apigenin Induces Apoptosis and Blocks Growth of Medroxyprogesterone Acetate-Dependent BT-474 Xenograft Tumors

Posttranslational Regulation of NF-YA Modulates NF-Y Transcriptional Activity

Block of Nuclear Receptor Ubiquitination

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