Transcription factor FBI-1 acts as a dual regulator in adipogenesis by coordinated regulation of cyclin-A and E2F-4
| Autor: | U. Leeser, M. Udelhoven, R. Bilkovski, Andrea Droste, Wilhelm Krone, F. Oberhauser, Matthias Laudes, Matthias Gomolka |
|---|---|
| Rok vydání: | 2008 |
| Předmět: |
Sp1 Transcription Factor
Endocrinology Diabetes and Metabolism Cyclin A Regulator Mitosis Repressor Histone Deacetylase 1 CHO Cells E2F4 Transcription Factor Histone Deacetylases Cricetulus Cell Line Tumor Cricetinae Drug Discovery Adipocytes Animals Humans SIN3A Promoter Regions Genetic E2F Transcription factor Genetics (clinical) Adipogenesis Models Genetic biology Effector Chemistry Cell cycle Molecular biology Clone Cells Cell biology DNA-Binding Proteins Gene Expression Regulation Neoplastic Repressor Proteins Sin3 Histone Deacetylase and Corepressor Complex biology.protein Molecular Medicine Transcription Factors |
| Zdroj: | Diabetologie und Stoffwechsel. 3 |
| ISSN: | 1861-9010 1861-9002 |
| DOI: | 10.1055/s-2008-1076217 |
| Popis: | Aims: Generation of new adipocytes plays a major role in the development of obesity. We previously have shown that transcriptional repressor FBI-1 exerts a dual effect in the process of adipogenesis by inhibiting proliferation and promoting differentiation of preadipocytes. The aim of the present study was to identify FBI-1 regulated molecular effectors which could account for these effects. Methods: In order to investigate the effect of FBI-1 on human cyclin A and E2F-4 promoter activity, dual-luciferase assays as well as EMSA and ChIP assays were performed in pEGFP-FBI-1 overexpressing and control cells. For expression profiling of potential FBI-1 co-repressors during adipogenesis, 3T3-L1 cells were differentiated into mature fat cells and HDAC-1, HDAC-2 and Sin3A levels were examined by western blotting at different time points of the differentiation process. Finally, using co-immunoprecipitation studies the interaction of pEGFP-FBI-1 and co-repressors was investigated. Results: Overexpressing FBI-1 in preadipocytes resulted in reduced expression of the cell cycle regulator cyclin A, which may explain FBI-1 induced inhibition of proliferation. Interestingly, FBI-1 repressed cyclin A promoter activity through an indirect mechanism that did not involve direct binding of FBI-1 to the promoter sequence, but rather FBI-1 inhibition of transcriptional activator Sp1 binding to a regulatory element at -452 to -443. We also show that FBI-1 promotes terminal preadipocyte differentiation through a mechanism involving decreased levels of expression of the PPARγ inhibitor E2F-4. FBI-1 significantly reduced E2F-4 promoter activity. Contrary to cyclin A, we found FBI-1 induced repression of E2F-4 is mediated by a direct mechanism via a FBI-1 regulatory element at -11 to -5. Since function of transcriptional repressors normally depends on the presence of regulatory co-factors we also performed expression profiling of potential FBI-1 co-repressors throughout adipogenesis. In these experiments Sin3A and HDAC-1 showed a similar expression pattern compared to FBI-1. Strikingly, co-immunoprecipitation studies revealed that FBI-1 binds Sin3A and HDAC-1 to form a repressor complex. Furthermore, by mutational analysis the aminoterminal POZ domain of FBI-1 was found to be important for Sin3A and HDAC-1 binding. Conclusions: Taken together, FBI-1 is the first transcriptional repressor shown to act as a dual regulator in adipogenesis exerting repressor activities on target genes by both, direct and indirect mechanisms. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|