2005 Fiscal Year Final Research Report Summary
An analysis of physiological roles of a new transcriptional coactivator of the PPAR family
| Project/Area Number |
16590865
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Metabolomics
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| Research Institution | Gunma University |
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Principal Investigator |
SATOH Teturou Gunma University, Medicine and Molecular Science, Assistant professor, 医学部, 助手 (40302484)
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| Project Period (FY) |
2004 – 2005
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| Keywords | PPAR / transcriptional coactivator / PRIC285 / alternative splicing / isoform / adipocyte / macrophage / nuclear receptors |
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| Research Abstract |
Using the DNA-binding domain (DBD) and the hinge region of human PPARγ as bait in yeast two-hybrid screen, we isolated partial cDNA identical to that of the C-terminal of KIAA1769. KIAA1769 encodes a 2,080-amino acid protein (MW:231kDa) that was recently identified to interact with PPARα and termed PPARα-interacting cofactor 285 (here referred to as PPARγ-DBD-interacting protein1α, PDIP1α. PDIP1 mRNA was expressed in 3T3-L1adipocytes and THP-1 macrophages. We also identified the expression of the N-terminal extended form of PDIP1α (referred to as PDIP1β) consisting of 2,649 amino acids (295kDa) in human cultured cell lines by RT-PCR and 5' RACE. RNase protection assay revealed that PDIP1β mRNA was expressed more abundantly than PDIP1α mRNA. The C-terminal region of PDIP1 directly binds DBD of PPARγ, and multiple LXXLL motifs in PDIP1 were not required for the interaction. PDIP1α and β similarly enhanced PPARγ-mediated transactivation in transfection assays and short interfering RNA targeting PDIP1 mRNA significantly reduced transactivation by PPARγ. No potent intrinsic activation domain was identified in either PDIP1 isoforms in mammalian one-hybrid assays and mutation of all LXXLL motifs did not affect enhancement of PPARγ-mediated transactivation. PDIP1α and β similarly augmented transactivation by PPARα, PPARδ, TRα1, TRβ1, and RXRα. PDIP1α also enhanced ERα- and AR-mediated transactivation, whereas PDIP1β did not. PDIP1α showed receptor-specific synergism with activation function (AF) 2-interacting coactivators in PPARγ- and TRβ1-mediated transactivation. Together, PDIP1 might function as a transcriptional cofactor for a broad range of nuclear receptors, possibly in collaboration with specific AF2 interacting coactivators.
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