|
KMID : 0380219990320030279
|
|
Journal of Biochemistry and Molecular Biology
1999 Volume.32 No. 3 p.279 ~ p.287
|
|
|
Ligand and Dimerization Dependent Transactivation Capability of Aromatic Hydrocarbon Receptor
|
|
Park Hyun-Sung
|
|
|
Abstract
|
|
|
|
The aromatic hydrocarbon receptor (AhR) is a cytosolic protein that binds the environmental pollutant, dioxin. The liganded AhR translocates into the nucleus where it heterimerizes with a constitutive nuclear protein, AhR nuclear translocator (Arnt). The N-terminal regions of both AhR and Arnt contain basic helix-loop-helix (bHLH) and Per-AhR-Arnt-Sim (PAS) motifs that are required for DNA binding, dimerization, and ligand binding whereas the C-terminal regions of both AhR and Arnt contain transactivation domains. Here, results from the mammalian two-hybrid system indicate that Arnt can make a homodimer but AhR cannot. In the presence of dioxin, the interaction between AhR and Arnt is stronger than that of the Arnt homodimer, suggesting that Arnt prefers to make a heterodimer with the liganded AhR rather than a homodimer. Transfection analyses using the GAL4-driven reporter system suggest that AhR's N-terminal region represses its own transactivation domain, as well as exogenous transactivation domains such as Sp 1 and VP16. Interestingly, the repressed transactivation domains of AhR are activated by ligand-dependent heterodimerization with Arnt. These observations suggest that heterodimerzation with Arnt is necessary not only for DNA binding but also for activation of the repressed transactivation capability of AhR.
|
|
|
KEYWORD
|
|
|
AhR, Arnt, Dioxin, Heterodimerization, Transactivation
|
|
|
FullTexts / Linksout information
|
|
|
|
|
|
Listed journal information
|
|
|
|
|