Abstract | BACKGROUND:
Granulosa cell tumors ( GCT) of the ovary often express aromatase and synthesize estrogen, which in turn may influence their progression. Recently a specific point mutation (C134W) in the FOXL2 protein was identified in >94% of adult-type GCT and it is likely to contribute to their development. A number of genes are known to be regulated by FOXL2, including aromatase/CYP19A1, but it is unclear which are direct targets and whether the C134W mutation alters their regulation. Recently, it has been reported that FOXL2 forms a complex with steroidogenic factor 1 (SF-1) which is a known regulator of aromatase in granulosa cells. METHODOLOGY/PRINCIPAL FINDINGS: In this work, the human GCT-derived cell lines KGN and COV434 were heterozygous and wildtype for the FOXL2:C134W mutation, respectively. KGN had abundant FOXL2 mRNA expression but it was not expressed in COV434. Expression of exogenous FOXL2:C134W in COV434 cells induced higher expression of a luciferase reporter for the ovarian specific aromatase promoter, promoter II (PII) (-516bp) than expression of wildtype FOXL2, but did not alter induction of a similar reporter for the steroidogenic acute regulatory protein (StAR) promoter (-1300bp). Co-immunoprecipitation confirmed that FOXL2 bound SF-1 and that it also bound its homologue, liver receptor homologue 1 (LRH-1), however, the C134W mutation did not alter these interactions or induce a selective binding of the proteins. A highly conserved putative binding site for FOXL2 was identified in PII. FOXL2 was demonstrated to bind the site by electrophoretic mobility shift assays (EMSA) and site-directed mutagenesis of this element blocked its differential induction by wildtype FOXL2 and FOXL2:C134W. CONCLUSIONS/SIGNIFICANCE: These findings suggest that aromatase is a direct target of FOXL2:C134W in adult-type GCT via a single distinctive and highly conserved binding site in PII and therefore provide insight into the pathogenic mechanism of this mutation.
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Authors | Nicholas I Fleming, Kevin C Knower, Kyren A Lazarus, Peter J Fuller, Evan R Simpson, Colin D Clyne |
Journal | PloS one
(PLoS One)
Vol. 5
Issue 12
Pg. e14389
(Dec 20 2010)
ISSN: 1932-6203 [Electronic] United States |
PMID | 21188138
(Publication Type: Journal Article, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, Non-P.H.S.)
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Chemical References |
- FOXL2 protein, human
- Forkhead Box Protein L2
- Forkhead Transcription Factors
- Phosphoproteins
- steroidogenic acute regulatory protein
- Aromatase
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Topics |
- Aromatase
(metabolism)
- Binding Sites
- Cell Line, Tumor
- Female
- Forkhead Box Protein L2
- Forkhead Transcription Factors
(genetics)
- Gene Expression Regulation, Neoplastic
- Granulosa Cell Tumor
(metabolism)
- Humans
- Mutagenesis, Site-Directed
- Mutation
- Ovarian Neoplasms
(genetics)
- Phosphoproteins
(genetics)
- Point Mutation
- Promoter Regions, Genetic
- Regulatory Sequences, Nucleic Acid
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