1998 Fiscal Year Final Research Report Summary
Cross-talk among nuclear receptor heterodimers
| Project/Area Number |
08671145
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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 |
内分泌・代謝学
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| Research Institution | Shinshu University |
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Principal Investigator |
MIYAMOTO Takahide Shinshu University School of Medicine Department of Geriatrics, Assistant Prof., 医学部・老年科, 助手 (20192768)
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| Co-Investigator(Kenkyū-buntansha) |
ICHIKAWA Kazuo Shinshu University School of Medicine Department of Geriatrics, Lecturor, 医学部, 講師 (40159835)
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| Project Period (FY) |
1996 – 1998
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| Keywords | Nclear Receptor / Thyroid hormone / Retinoic Acid / Yeast Two Hybrid / co-activator / co-reprossor |
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| Research Abstract |
The thyroid hormone receptors (TR) are ligand-dependent, DNA binding, trans-acting transcriptional factors belonging to the erbA-related steroid/thyroid hormnone receptor superfamily, TRs bind to cis-acting DNA elements as heterodimers with the retinoid X receptors (RXR). These helerodimers display distinct specificities to mediate the hormonal response to target gene transcription. We characterized the interaction between TRalphal and RXRalpha via their ligand binding domains (LBD) and the effect of ligands on the interaction using a yeast two-hybrid system. The DNA binding domain (BD) of yeast Ga14 fusion to the LBD of TRalpha had no transcriptional activity on its own but, when co-expressed with the activation domain (AD) of yeast Ga14 fusion to LBD of RXR"a" conferred activation to a reporter gene harboring Ga14 binding site, indicating that LBDs of TRalpha1 and RXRalpha interact each other in solution. Furthermore, T3 and 9cis-RA increased the reporter activity and synergistic effect was observed when both ligands were added, indicating that the TRalpha/RXRalpha heterodimerization is augmented by their respective ligands in vivo. Using an in vitro pull down experiment, we confirmed the ligand dependent interaction observed in the yeast system. Matrix bound GST-RXRalpha specifically co-precipitated the ^<35>S-labeled TRalpha1 above the control and associated ^<35>S-labeled TRalpha1 was increased by addition of T3 and 9cis RA.This suggests that T3 induced -confrontational changes of TR required for the ligand dependent heterodimerization. These results imply a complex, sensitive cross-talk in vivo among nuclear receptors and their respective ligands through distinct hormonal signaling pathways.
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