1
|
Sidhu A, Miller PJ, Johanson KE, Hollenbach AD. Novel Flanking DNA Sequences Enhance FOXO1a DNA Binding Affinity but Do Not Alter DNA Bending. Biochemistry 2008; 47:6809-18. [DOI: 10.1021/bi702495m] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Affiliation(s)
- Alpa Sidhu
- Department of Genetics, Louisiana State University Health Sciences Center, 533 Bolivar Street, New Orleans, Louisiana 70112
| | - Patrick J. Miller
- Department of Genetics, Louisiana State University Health Sciences Center, 533 Bolivar Street, New Orleans, Louisiana 70112
| | - Kelly E. Johanson
- Department of Genetics, Louisiana State University Health Sciences Center, 533 Bolivar Street, New Orleans, Louisiana 70112
| | - Andrew D. Hollenbach
- Department of Genetics, Louisiana State University Health Sciences Center, 533 Bolivar Street, New Orleans, Louisiana 70112
| |
Collapse
|
2
|
Obendorf M, Meyer R, Henning K, Mitev YA, Schröder J, Patchev VK, Wolf SS. FoxG1, a member of the forkhead family, is a corepressor of the androgen receptor. J Steroid Biochem Mol Biol 2007; 104:195-207. [PMID: 17482455 DOI: 10.1016/j.jsbmb.2007.03.012] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The androgen receptor (AR) is a ligand-dependent transcriptional regulator which belongs to the nuclear receptor superfamily. The basal transcriptional activity of the androgen receptor is regulated by interaction with coactivator or corepressor proteins. The exact mechanism whereby comodulators influence target gene transcription is only partially understood, especially for corepressors. Whereas several coactivators are described for the AR, only a few corepressors are known. Here, we describe the discovery of a new androgen receptor corepressor, FoxG1, which belongs to the forkhead family. By using a fragment of the AR (aa 325-919) as bait in a yeast two hybrid screen, the C-terminal region (aa 175-489) of FoxG1 (also known as BF1), was identified as AR-interacting protein. Binding of AR to the FoxG1 fragment was verified by one- and two-hybrid assays, and pull-down experiments. In addition, we show that the full-length form of FoxG1 functions as a strong corepressor in the AR-mediated transactivation. The FoxG1 expression profile in adult individuals is restricted to brain and testis in human and decreases during aging in the rodent brain. Both AR and FoxG1 expression are developmentally regulated. Besides its reported role in neurogenesis, the strong expression of FoxG1 in AR-abundant areas of the adult brain suggests possible involvement in neuroendocrine regulation. Taken together, the data presented suggest that, in addition to repression of transcription by direct binding to DNA, FoxG1 may interact with AR in vivo, thereby targeting its repressor function specifically to sex hormone signaling.
Collapse
Affiliation(s)
- Maik Obendorf
- Schering AG/Jenapharm GmbH&Co.KG, CRBA G&A, Otto-Schott-Str. 15, D-07745 Jena, Germany.
| | | | | | | | | | | | | |
Collapse
|
3
|
Lee JW, Kusumoto R, Doherty KM, Lin GX, Zeng W, Cheng WH, von Kobbe C, Brosh RM, Hu JS, Bohr VA. Modulation of Werner syndrome protein function by a single mutation in the conserved RecQ domain. J Biol Chem 2005; 280:39627-36. [PMID: 16150736 DOI: 10.1074/jbc.m506112200] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Naturally occurring mutations in the human RECQ3 gene result in truncated Werner protein (WRN) and manifest as a rare premature aging disorder, Werner syndrome. Cellular and biochemical studies suggest a multifaceted role of WRN in DNA replication, DNA repair, recombination, and telomere maintenance. The RecQ C-terminal (RQC) domain of WRN was determined previously to be the major site of interaction for DNA and proteins. By using site-directed mutagenesis in the WRN RQC domain, we determined which amino acids might be playing a critical role in WRN function. A site-directed mutation at Lys-1016 significantly decreased WRN binding to fork or bubble DNA substrates. Moreover, the Lys-1016 mutation markedly reduced WRN helicase activity on fork, D-loop, and Holliday junction substrates in addition to reducing significantly the ability of WRN to stimulate FEN-1 incision activities. Thus, DNA binding mediated by the RQC domain is crucial for WRN helicase and its coordinated functions. Our nuclear magnetic resonance data on the three-dimensional structure of the wild-type RQC and Lys-1016 mutant proteins display a remarkable similarity in their structures.
Collapse
Affiliation(s)
- Jae Wan Lee
- Laboratory of Molecular Gerontology, NIA, National Institutes of Health, Baltimore, Maryland 21224-6825, USA
| | | | | | | | | | | | | | | | | | | |
Collapse
|
4
|
Abstract
The winged helix transcription factor FoxG1 (Bf-1, qin) plays multiple roles in the development of the telencephalon, with different parts of the protein affecting either proliferation or differentiation. We examined the consequences of over-expression, via retroviral expression, of FoxG1 on the growth of different regions of the chicken brain. Excess expression of FoxG1 caused a thickening of the neuroepithelium, and ultimately large outgrowths of the telencephalon and mesencephalon. In contrast, the myelencephalon appeared unaffected, exhibiting normal apoptosis and growth characteristics. A DNA binding defective form of FoxG1 did not exhibit these abnormalities, suggesting that these effects are due to FoxG1's function as a transcriptional repressor. To examine the means by which excess FoxG1 caused overgrowth of the brain, we examined alterations in cell proliferation and death. No increase in proliferation was noted in any portion of the neural tube, rather a significant decrease in neuroepithelial apoptosis was seen. These results demonstrate a previously unrecognized role for winged helix factors in the regulation of neural cell apoptosis.
Collapse
Affiliation(s)
- Sara Ahlgren
- Division of Biology 139-74, California Institute of Technology, Pasadena, California 91125, USA.
| | | | | |
Collapse
|
5
|
Krupczak-Hollis K, Wang X, Dennewitz MB, Costa RH. Growth hormone stimulates proliferation of old-aged regenerating liver through forkhead box m1b. Hepatology 2003; 38:1552-62. [PMID: 14647066 DOI: 10.1016/j.hep.2003.08.052] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The Forkhead Box (Fox) proteins are an extensive family of transcription factors that shares homology in the winged helix DNA-binding domain and the members of which play essential roles in cellular proliferation, differentiation, and longevity. Reduced cellular proliferation during aging is associated with a progressive decline in both growth hormone (GH) secretion and Foxm1b expression. Liver regeneration studies with 12-month-old (old-aged) transgenic mice indicated that increased hepatocyte expression of Foxm1b alone is sufficient to restore hepatocyte proliferation to levels found in 2-month-old (young) regenerating liver. GH therapy in older people has been shown to cause an increase in cellular proliferation, but the transcription factors that mediated this stimulation in proliferation remain uncharacterized. In this study, we showed that human GH administration to old-aged Balb/c mice dramatically increased both expression of Foxm1b and regenerating hepatocyte proliferation. This increase in old-aged regenerating hepatocyte proliferation was associated with elevated protein expression of Cdc25A, Cdc25B, and cyclin B1, with reduced protein levels of cyclin-dependent kinase inhibitor p27(Kip1) (p27). GH treatment also was found to stimulate hepatocyte proliferation and expression of Foxm1b protein without partial hepatectomy (PHx). Furthermore, GH treatment of young Foxm1b -/- mice failed to restore regenerating hepatocyte DNA replication and mitosis caused by Foxm1b deficiency. These genetic studies provided strong evidence that the presence of Foxm1b is essential for GH to stimulate regenerating hepatocyte proliferation. In conclusion, our old-aged liver regeneration studies show that increased Foxm1b levels are essential for GH to stimulate hepatocyte proliferation, thus providing a mechanism for GH action in the elderly.
Collapse
Affiliation(s)
- Katherine Krupczak-Hollis
- Department of Molecular Genetics, University of Illinois at Chicago College of Medicine, Chicago, IL 60607-7170, USA
| | | | | | | |
Collapse
|
6
|
Sonderegger CK, Narisawa-Saito M, Vogt PK. The C-terminal region of cellular Qin oligomerizes: correlation with oncogenic transformation and transcriptional repression. Oncogene 2003; 22:1908-15. [PMID: 12673196 DOI: 10.1038/sj.onc.1206307] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Expression of the oncoprotein Qin induces tumors in chickens and oncogenic transformation of chicken embryo fibroblasts in culture. We performed a detailed deletion analysis of the C-terminal region of Qin (amino acids 246-451, extending from the winged helix domain to the C-terminus) and identified amino acids 246-379 as important for transformation. The same region mediates homo-oligomerization of Qin as documented in vitro by GST pulldowns and in vivo by coimmunoprecipitation. A 60 amino-acid region within the oligomerization domain is necessary and sufficient for transcriptional repression induced by Qin.
Collapse
Affiliation(s)
- Corinna K Sonderegger
- Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, CA 92037, USA
| | | | | |
Collapse
|
7
|
Sonderegger CK, Vogt PK. Binding of the corepressor TLE1 to Qin enhances Qin-mediated transformation of chicken embryo fibroblasts. Oncogene 2003; 22:1749-57. [PMID: 12660810 DOI: 10.1038/sj.onc.1206308] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The oncoprotein Qin is a member of the winged helix family of transcriptional regulators. The region C-terminal to its winged helix DNA-binding domain is required for transformation of chicken embryo fibroblasts. We isolated the corepressor TLE1 as a binding partner for Qin in a yeast two-hybrid screen and localized the TLE1-binding region to a 60 amino-acid stretch directly C-terminal of the winged helix domain of Qin. We show in vivo interaction of full-length Qin and TLE1 in a mammalian two-hybrid system. Coexpression of TLE1-binding Qin and TLE1 induces phosphorylation of TLE1. The DNA-binding activity of Qin is not required for this function. Binding of Qin to TLE1 correlates with Qin-induced transformation. Addition of the TLE1-binding motif WRPW to the C-terminus of a transformation-defective Qin deletion mutant restores binding to TLE1 and significantly enhances transformation. Expression of TLE1 in CEF by the retroviral vector RCAS enhances cell growth and induces formation of agar colonies.
Collapse
Affiliation(s)
- Corinna K Sonderegger
- Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, CA 92037, USA
| | | |
Collapse
|
8
|
Wang X, Kiyokawa H, Dennewitz MB, Costa RH. The Forkhead Box m1b transcription factor is essential for hepatocyte DNA replication and mitosis during mouse liver regeneration. Proc Natl Acad Sci U S A 2002; 99:16881-6. [PMID: 12482952 PMCID: PMC139238 DOI: 10.1073/pnas.252570299] [Citation(s) in RCA: 268] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2002] [Indexed: 12/30/2022] Open
Abstract
The Forkhead Box (Fox) proteins are an extensive family of transcription factors that shares homology in the winged helix DNA-binding domain and whose members play essential roles in cellular proliferation, differentiation, transformation, longevity, and metabolic homeostasis. Liver regeneration studies with transgenic mice demonstrated that FoxM1B regulates the onset of hepatocyte DNA replication and mitosis by stimulating expression of cell cycle genes. Here, we demonstrate that albumin-promoter-driven Cre recombinase-mediated hepatocyte-specific deletion of the Foxm1b Floxed (fl) targeted allele resulted in significant reduction in hepatocyte DNA replication and inhibition of mitosis after partial hepatectomy. Reduced DNA replication in regenerating Foxm1b(-/-) hepatocytes was associated with sustained increase in nuclear staining of the cyclin-dependent kinase (Cdk) inhibitor p21(Cip1) (p21) protein between 24 and 40 h after partial hepatectomy. Furthermore, increased nuclear p21 levels and reduced expression of Cdc25A phosphatase coincided with decreases in Cdk2 activation and hepatocyte progression into S-phase. Moreover, the significant reduction in hepatocyte mitosis was associated with diminished mRNA levels and nuclear expression of Cdc25B phosphatase and delayed accumulation of cyclin B1 protein, which is required for Cdk1 activation and entry into mitosis. Cotransfection studies demonstrate that FoxM1B protein directly activated transcription of the Cdc25B promoter region. Our present study shows that the mammalian Foxm1b transcription factor regulates expression of cell cycle proteins essential for hepatocyte entry into DNA replication and mitosis.
Collapse
Affiliation(s)
- Xinhe Wang
- Department of Molecular Genetics, University of Illinois College of Medicine, 900 South Ashland Avenue, Chicago, IL 60607, USA
| | | | | | | |
Collapse
|
9
|
Brain factor-1 controls the proliferation and differentiation of neocortical progenitor cells through independent mechanisms. J Neurosci 2002. [PMID: 12151532 DOI: 10.1523/jneurosci.22-15-06526.2002] [Citation(s) in RCA: 136] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The winged helix gene Brain factor-1 (BF1) has a pleiotropic role in the development of the cerebral hemispheres of the brain. Mice lacking BF1 have defects in the morphogenesis of the structures of the dorsal telencephalon (e.g., neocortex) and the ventral telencephalon (e.g., the basal ganglia). This study focuses on the functions of BF1 in the dorsal telencephalon. We showed previously that telencephalic progenitor cells lacking BF1 differentiate into neurons prematurely. Here, we demonstrate that the loss of BF1 also results in an early lengthening of the cell cycle in neocortical progenitors. To investigate the mechanisms by which BF1 regulates progenitor cell proliferation and differentiation in the developing brain, we have replaced the endogenous BF1 protein with a DNA binding defective form of BF1 in mice, BF1(NHAA). The BF1(NHAA) protein restores the growth of the dorsal telencephalon, by improving the proliferation of progenitor cells. However, the BF1(NHAA) protein does not correct the early neuronal differentiation associated with the loss of BF1. In contrast, replacement of endogenous BF1 with wild-type BF1 corrects the defects in both the proliferation and differentiation of neocortical progenitors. These results demonstrate that BF1 controls progenitor cell proliferation and differentiation in the neocortex through distinct DNA binding-independent and binding-dependent mechanisms.
Collapse
|
10
|
Wang X, Quail E, Hung NJ, Tan Y, Ye H, Costa RH. Increased levels of forkhead box M1B transcription factor in transgenic mouse hepatocytes prevent age-related proliferation defects in regenerating liver. Proc Natl Acad Sci U S A 2001; 98:11468-73. [PMID: 11572993 PMCID: PMC58753 DOI: 10.1073/pnas.201360898] [Citation(s) in RCA: 169] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2001] [Indexed: 12/22/2022] Open
Abstract
The forkhead box (Fox) family of transcription factors share homology in the winged helix/forkhead DNA-binding domain and play important roles in regulating cellular proliferation, differentiation, longevity, and cellular transformation. Forkhead box M1B (FoxM1B) is a ubiquitously expressed member of the Fox transcription factor family whose expression is restricted to proliferating cells and that mediates hepatocyte entry into DNA synthesis and mitosis during liver regeneration. Recent cDNA microarray studies indicated that age-related defects in cellular proliferation are associated with diminished expression of the FoxM1B transcription factor. Here, we show that increased levels of FoxM1B in regenerating liver of old transgenic mice restore the sharp peaks in hepatocyte DNA replication and mitosis that are the hallmarks of young regenerating mouse liver. Restoration of the young regenerating liver phenotype is associated with increased expression of numerous cell cycle regulatory genes that include cyclin D1, cyclin A2, cyclin F, cyclin B1, cyclin B2, Cdc25B, and p55cdc. Cotransfection assays in the human hepatoma HepG2 cell line demonstrated that FoxM1B protein stimulated expression of both the cyclin B1 and cyclin D1 promoters, suggesting that these cyclin genes are a direct FoxM1B transcriptional target. These results suggest that FoxM1B controls the transcriptional network of genes that are essential for cell division and exit from mitosis. Our results indicate that reduced expression of the FoxM1B transcription factor contributes to the decline in cellular proliferation observed in the aging process.
Collapse
Affiliation(s)
- X Wang
- Department of Molecular Genetics, University of Illinois, College of Medicine, 900 South Ashland Avenue, Chicago, IL 60607-7170, USA
| | | | | | | | | | | |
Collapse
|