Differentiation response element

A most important function of vitamin A is in the control of cell differentiation and mrnover. PsA-trans-retinoic acid and 9-cw-retinoic acid (Figure 45-1) regulate growth, development, and tissue differentiation they have different actions in different tissues. Like the steroid hormones and vitamin D, retinoic acid binds to nuclear receptors that bind to response elements of DNA and regulate the transcription of specific genes. There are two families of nuclear retinoid receptors the retinoic acid receptors (RARs) bind all-rrijw-retinoic acid or 9-c -retinoic acid, and the retinoid X receptors (RXRs) bind 9-cw-retinoic acid. 

Wildlife toxicologists should be attuned to developments in human health mercury, as assays that have been used successfully on humans may be suitable or adaptable for other vertebrate species. Echeverria and co-workers (Echeverria et al. 2005, 2006 Heyer et al. 2006) have characterized a gene encoding coproporphyrinogen oxidase, a gene in the heme biosynthetic pathway. Polymorphism in this gene predicts differential response to elemental mercury exposure in human subjects. Plans to modify this assay for other mercury species in matrices from wildlife are under way. 

Retinol and retinoic acid are required for the growth, differentiation, and maintenance of epithelial cells. In this capacity they bind intracellular receptors, which are in the family of Zn-finger proteins, and they regulate transcription through specific response elements. 

Figure 10. Transverse section of coalified Cyrilla wood through wound tissue. Note differential response of the thick fiber wall layers to coalification. The outermost wall layers have produced an isotropic, orange-brown material whereas the bulk of the secondary wall has yielded a pale yellowy strongly anisotropic coal substance. A ring of dark red material has been produced from the inner secondary wall in the fiber-tracheid shown in the left center of the photograph and a semiopaque, granular product is seen in an adjacent iracheary element. 323X...

P7. Pennie, W. D., Aldridge, T. C., and Brooks, K. N., Differential activation by xenoestrogens of ER alpha and ER beta when linked to different response elements. J. Endocrinol. 158, R11-R14 (1998). 

The structural design of retinoic acid receptors explains, at least in part, the pleiotropy of this class of receptors. It is a consequence of the combinatorial possibilities offered by heterodimerization. The many different functional units that can be formed by heterodimerization make it understandable why so many different gene response elements can be recognized. This, and a distinct spatiotemporal pattern of expression, both in the developing embryo and in differentiated tissues, suggests that each RAR and RXR isoform and each heterodimer formed may have a unique function. Pierre Chambon has directed attention to the large repertoire of combinatorial arrangements. These combina-... 

Damodaran, T.V., Abdel-Rahman, A.A., Suliman, H.B., Ahou-Donia, M.B. (2002c). Early differential elevation and persistence of phosphorylated cAMP-response element binding protein (p-CREB) in the central nervous system of hens treated with diisopropyl phosphorofluoridate, an OPIDN-causing compound. Neurochem. Res. 27 183-93. 

Kim, Y.C., Masutani, H., Yamaguchi, Y, Itoh, K., Yamamoto, M., and Yodoi, J., Hemin-induced activation of the thioredoxin gene by Nrf2. A differential regulation of the antioxidant responsive element by a switch of its binding factors, J. Biol Chem., 276, 18399-18406, 2001. 

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