adopted from:( www.fas.harvard.edu/~mcb155)
FUNCTION:
Enhanceosomes are stereo-specific enhancer complexes. Most eukaryotic transcriptional enhancers contain binding sites for multiple distinct activator proteins. The enhancer is organized in a manner based on the mechanism which allows for selective activation of genes in response to extracellular signals. A precise arrangement of activator binding sites are required to make the interaction a synergistic interaction. This synergy that is achieved is due to the cooperative assembly and the increased stability of the enhanceosome complex. The steriospecific assembly is a vital factor in the efficient and specific recruitment of the transcriptional apparatus to the promoter.
ATF-2 is a transcription factor that is a DNA binding protein that binds specifically to the cyclic AMP response elements (CREās). ATF-2 can bind as a homodimer, or a heterodimer with c-jun. When bound the ATF-2 stimulates CRE dependent transcription. ATF-2 plays a vital role in the functionality of the enhanceosome complex. The ATF-2 binds as a dimer to the c-jun to form a heterodimer which is directly responsible for the structure of the enhanceosome. ATF-2 and c-jun bind to positive regulatory domains II and IV (PRDII and PRDIV). The correct assembly of the IFN- depends on the correct spatial placement of the PRDās.
(Source: Falvo, J. et al.)
This is a still shot of the active site of ATF-2. It can be accessed
at the Protein data bank (1BHI).
This is a picture of the ATF recognition site, it is available on the protein data bank, as 1SAA.
REFERENCES:
James V. Falvo, Bhavin S. Parekh, Charles H. Lin, Ernest Fraenkel,
and Tom Maniatis; Assembly of a Functional Beta Interferon Enhanceosome
Is Dependent on ATF-2-c-jun Heterodimer Orientation, Molecular and Cellular
Biology, July 2000, p. 4814-4825, Vol. 20, No. 13
Taeil Kim, Tae Young Kim, Woo Ghil Lee, Jeongbin Yim, and Tae Kook Kim; Signaling Pathways to the Assembly of an Interferon-? Enhanceosome; J. Biol. Chem., Vol. 275, Issue 22, 16910-16917, June 2, 2000
Kawasaki, Hiroaki, Schiltz, Lou, Chiu, Robert, Itakura, Keiichi, Taira, Kazunari, Nakatani, Yoshihiro, et. al.; ATF-2 has intrinsic histone acetyltransferase activity which is modulated by phosphorylation; Nature 405, 195 - 200 (2000) © Macmillan Publishers Lt
