| 1. |
- Damdimopoulos, Anastasios E., et al.
(författare)
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An alternative splicing variant of the selenoprotein thioredoxin reductase is a modulator of estrogen signaling
- 2004
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Ingår i: Journal of Biological Chemistry. - : American Society for Biochemistry and Molecular Biology. - 0021-9258 .- 1083-351X. ; 279:37, s. 38721-38729
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Tidskriftsartikel (refereegranskat)abstract
- The selenoprotein thioredoxin reductase (TrxR1) is an integral part of the thioredoxin system. It serves to transfer electrons from NADPH to thioredoxin leading to its reduction. Interestingly, recent work has indicated that thioredoxin reductase can regulate the activity of transcription factors such as p53, hypoxia-inducible factor, and AP-1. Here, we describe that an alternative splicing variant of thioredoxin reductase (TrxR1b) containing an LXXLL peptide motif, is implicated in direct binding to nuclear receptors. In vitro interaction studies revealed direct interaction of the TrxR1b with the estrogen receptors alpha and beta. Confocal microscopy analysis showed nuclear colocalization of the TrxR1b with both estrogen receptor alpha and beta in estradiol-17beta-treated cells. Transcriptional studies demonstrated that TrxR1b can affect estrogen-dependent gene activation differentially at classical estrogen response elements as compared with AP-1 response elements. Based on these results, we propose a model where thioredoxin reductase directly influences the estrogen receptor-coactivator complex assembly on non-classical estrogen response elements such as AP-1. In summary, our results suggest that TrxR1b is an important modulator of estrogen signaling.
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| 2. |
- Ehrlund, Anna, et al.
(författare)
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Knockdown of SF-1 and RNF31 affects components of steroidogenesis, TGFβ, and Wnt/β-catenin signaling in adrenocortical carcinoma cells.
- 2012
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Ingår i: PloS one. - : Public Library of Science (PLoS). - 1932-6203. ; 7:3, s. e32080-
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Tidskriftsartikel (refereegranskat)abstract
- The orphan nuclear receptor Steroidogenic Factor-1 (SF-1, NR5A1) is a critical regulator of development and homeostasis of the adrenal cortex and gonads. We recently showed that a complex containing E3 ubiquitin ligase RNF31 and the known SF-1 corepressor DAX-1 (NR0B1) interacts with SF-1 on target promoters and represses transcription of steroidogenic acute regulatory protein (StAR) and aromatase (CYP19) genes. To further evaluate the role of SF-1 in the adrenal cortex and the involvement of RNF31 in SF-1-dependent pathways, we performed genome-wide gene-expression analysis of adrenocortical NCI-H295R cells where SF-1 or RNF31 had been knocked down using RNA interference. We find RNF31 to be deeply connected to cholesterol metabolism and steroid hormone synthesis, strengthening its role as an SF-1 coregulator. We also find intriguing evidence of negative crosstalk between SF-1 and both transforming growth factor (TGF) β and Wnt/β-catenin signaling. This crosstalk could be of importance for adrenogonadal development, maintenance of adrenocortical progenitor cells and the development of adrenocortical carcinoma. Finally, the SF-1 gene profile can be used to distinguish malignant from benign adrenocortical tumors, a finding that implicates SF-1 in the development of malignant adrenocortical carcinoma.
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| 3. |
- Loinder, Kristina, 1963-
(författare)
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Nuclear receptor corepressor N-CoR : role in transcriptional repression
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The human body consists of a multitude of cells of varying appearance and function. With a few exceptions they are genetically identical, and the key to their divergence lies in their different specific patterns of gene expression. Gene expression may be regulated at the level of transcription, in two opposing directions; either activation or repression. Gene transcription is controlled by transcription factors, which bind to regulatory DNA sequences, and direct gene expression in concert with auxiliary proteins. Among these the nuclear receptor corepressor N-CoR holds a central position. It serves as a docking unit between many different DNA-bound transcription factors, such as nuclear receptors, and large complexes of repressor proteins. Many repressor complexes of distinct compositions have been shown to contain N-CoR.N-CoR plays a vital part in normal fetal development, and its involvement has been implicated in several pathological conditions. It has been shown to interact with unliganded nuclear receptors via CoRNR-box motifs in the C-terminal half of the protein. We have identified an NR-box motif, typical of coactivators, in the N-terminal part of N-CoR, which we have shown to be capable of interacting with the nuclear receptors RARα and TRß both in vitro and in vivo. A mutated NR-box motif did not interact accordingly. We discovered that the NR-box motif found in N-CoR displayed a ligand-dependent interaction with TRß in GST pulldown experiments, and that the immediate NR-box environment in N-CoR resembles NRbox environments in the coactivator CBP. We investigated a possible role for theN-CoR NRbox motif in regulation of the TSHß gene from a negative TR response element found in its promoter. In transient transfectiqns of GH3 cells, we found that both TRß3 and N-CoR are necessary for ligand-induced repression from this response element to occur. Mutating the NR-box abolished the repressive potential of N-CoR. The results were corroborated by results from transient transfections of HEK293/T cells, where siRNA-targeted degradation of endogenous N-CoR mRNA annihilated the ligand-induced repression, and where wild type mouse N-CoR but not mutated N-CoR restored the repression. In vitro binding assays also showed that TR, bound to its negative response element in the TSHß gene promoter, displayed an obligate ligand dependence in its interaction with N-CoR.In several different leukemias N-CoR holds a key role. Abberant transcription factors bind stronger toN-CoR than their normal counterparts, leading to constitutive repression of key genes in hematopoiesis. Retinoid signaling, mediated by RARs plays a central part in differentiation of myeloid cells. We therefore investigated the extent of N-CoR expression in the myeloid cell line THP-1 during differentiation. Analyses both at mRNA- and at protein level showed that N-CoR expression was down-regulated as the myeloid cells differentiated. Exploring the effects of this on genes controlled by retinoic acid, we found in transient transfections of THP-1 cells that N-CoR modulated the expression level both at basal and at ligand-activated level. Several reports by others have also emphasized the importance of relative levels of different coregulatory proteins for determining the amplitude of the transcriptional response.N-CoR binds both to transcription factors and to repressor complexes, but so far no report has been published regarding its possible DNA-binding capacity, anticipated by analysis of its amino acid sequence. Employing the selected and amplified binding sites (SAAB) assay we showed that N-CoR bound to DNA. Sequence determination resulted in the identification of a DNA sequence, ATNNTNCTC, which binds specifically toN-CoR. This finding adds another variable in the spectrum of N-CoR interactions.
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| 4. |
- Massinen, Satu, et al.
(författare)
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Functional interaction of DYX1C1 with estrogen receptors suggests involvement of hormonal pathways in dyslexia
- 2009
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Ingår i: Human Molecular Genetics. - : Oxford University Press (OUP). - 0964-6906 .- 1460-2083. ; 18:15, s. 2802-2812
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Tidskriftsartikel (refereegranskat)abstract
- Dyslexia, or specific reading disability, is the unexpected failure in learning to read and write when intelligence and senses are normal. One of the susceptibility genes, DYX1C1, has been implicated in neuronal migration, but little is known about its interactions and functions. As DYX1C1 was suggested to interact with the U-box protein CHIP (carboxy terminus of Hsc70-interacting protein), which also participates in the degradation of estrogen receptors alpha (ERalpha) and beta (ERbeta), we hypothesized that the effects of DYX1C1 might be at least in part mediated through the regulation of ERs. ERs have shown to be important in brain development and cognitive functions. Indeed, we show that DYX1C1 interacts with both ERs in the presence of 17beta-estradiol, as determined by co-localization, co-immunoprecipitation and proximity ligation assays. Protein levels of endogenous ERalpha or exogenous ERbeta were reduced upon over-expression of DYX1C1, resulting in decreased transcriptional responses to 17beta-estradiol. Furthermore, we detected in vivo complexes of DYX1C1 with ERalpha or ERbeta at endogenous levels along neurites of primary rat hippocampal neurons. Taken together, our data suggest that DYX1C1 is involved in the regulation of ERalpha and ERbeta, and may thus affect the brain development and regulate cognitive functions. These findings provide novel insights into the function of DYX1C1 and link neuronal migration and developmental dyslexia to the estrogen-signaling effects in the brain.
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