| Budget Amount *help |
¥3,500,000 (Direct Cost: ¥3,500,000)
Fiscal Year 2005: ¥1,400,000 (Direct Cost: ¥1,400,000)
Fiscal Year 2004: ¥2,100,000 (Direct Cost: ¥2,100,000)
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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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