Dependent Transactivation

Tcf-1 and Lef-1 are not classical transcription factors in that they are incapable of activating transcription of reporter gene constructs from a synthetic enhancer containing multimerized Tcf/Lef binding sites. Lef-1 acts as 

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In another recent example, Hashimoto reported photoaffinity experiments on retinoic acid receptors (RAR). Retinoic acid plays a critical role in cell proliferation and differentiation. RARs belong to the superfamily of nuclear/ thyroid hormone receptors. They consist of six transmembrane domains (A-F) which is a general feature of these receptors. The A/B domains have an autonomous transactivation function while the C-domain contains the Zn-finger, which binds to DNA. The large E-domain participates in ligand binding, dimerization, and ligand dependent transactivation. Finally, D- and F-domains help the orientation and stabilization of the E-domain. 

Carballo-Jane E, Pandit S, Santoro JC, et al. Skeletal muscle a dual system to measure glucocorticoid-dependent transactivation and transrepression of gene regulation. J Steroid Biochem Mol Biol. 2004 88 191-201. 

In addition to the G(Vy subunit mechanism, the opioid receptor could increase the Erkl/2 activity via a transactivation process. Using receptor mutants that have impeded calmodulin binding activity, Belvecha et al. [106] demonstrated the activation of Erkl/2 by the mu opioid receptor involved the calmodulin-dependent transactivation of the EGF receptor. Such mechanism represents the participation of metalloproteases in producing the ligand for EGF receptor as in the case of p>2-adrcncrgic receptor [107]. Whether this is occurring with the neuronal delta opioid receptor remains to be demonstrated. 

Costet P, Luo Y, Wang N, et al. Sterol-dependent transactivation of the ABC1 promoter by the liver X receptor/retinoid X receptor. J Biol Chem 275 28240-28245, 2000. 

Lee Sk, Anzick SL, Choi JE, Bubendorf L, Guan XY, et al. 1999. A nuclear factor, ASC-2, as a cancer-amplified transcriptional coactivator essential for ligand-dependent transactivation by nuclear receptor in vivo. J. Biol. Chem. 274 34283-93... 

Auerbach SS, Stoner MA, Su S, Omiecinski CJ. Retinoid X receptor-a-dependent transactivation by a naturally occurring structural variant of human constitutive androstane receptor (NR1I3). Mol Pharmacol 2005 68 1239-53. 

Honjo, Y., Sasaki, S., Kobayashi, Y, Misawa, H., and Nakamura, H. (2006) 1,25-Dihydroxyvitamin D3 and its receptor inhibit the chenodeoxycholic acid-dependent transactivation by farnesoid X receptor. The Journal of Endocrinology, 188 (3), 635-643. 

Mar, E., Delgado-Rodrigues, E., Nguyen, P., Baxter, J.D., Buehrer, B.M., Webb, P., Fletterick, R.J. and Guy, R.K. (2005) The molecular mechanisms of coactivator utilization in ligand-dependent transactivation by the androgen receptor. The Journal of Biological Chemistry, 280, 8060-8068. 

Ogo, A., Waterman, M.R., Kamps, M.P., Kagawa, N. 1995. Protein kinase a-dependent transactivation by the e2a-pbxl fusion protein. J. Biol. Chem. 270, 25340-25343. 

SV23 characterized by a four amino acid insertion in the LBD adds an extra loop between helices 6 and 7. This isoform interacts weakly with CAR response elements and with various coactivators [61-65]. This variant was capable of transactivating CYP2B6 and MDR1 reporters in some studies but not CYP3A4 and IJGT1A1 reporters [61-65], Recently, it has been shown that upon RXRa overexpression SV23 shows RXR-dependent transactivation activity and interaction with SRC-1 as well as RXR-dependent response to clotrimazole and androstanol [66]. 

Barettino, D., M. D. M. Ruiz, and H. G. Stuimenberg. 1994. Characterization of the ligand-dependent transactivation domain of thyroid hormone receptor. EMBO Journal 13 3039-3049. 

Valentine, J.E., KaUdioven, E., White, R., Hoare, S., and Parker, M.G., Mutations in the estrogen receptor ligand binding domain discriminate between hormone-dependent transactivation and transrepression, J. Biol Chem., 275,25322-25329,2000. 

Red clover Inhibits DMBA-induced DNA isoflavone damage reduces CYPlAl and -biochanin A IBl mRNA and interference of (trifolium pratense) XRE-dependent transactivation MCF7 cells Chan, H.Y. etal.,5r. J. Nutr., 90, 87,2003... 

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