EXCEED THE SPACE PROVIDED. Retinoic acid (RA), the most potent natural form of vitamin A, plays an important role in mediating the growth and differentiation of both normal and transformed cells. Retinoic acid receptors (RARa, RARp and RARv) and retinoid X receptors (RXRa, RXRp and RXRv) have been identified and demonstrated to modulate the action of retinoids by regulating the transcription of specific target genes. In addition, several isoforms of each RAR isotype have been described. The long term goal of the proposed studies is to identify the unique structural and functional features of each of the three different RAR isotypes and their respective isoforms. An understanding of these unique structural and functional features will contribute to the ultimate development and application of retinoids targeted to an individual RAR isotype/isoform to elicit specific functions in the body potentially for dermatological and/or cancer chemotherapeutic/ chemopreventive treatments.
In Specific Aim 1, we will examine the unique structural features of the three RAR isotypes and their isoforms by addressing two specific questions. First, we will determine whether the region of the RAR ligand binding domains responsible for interaction with the carboxyl group of retinoids functions independently from or dependency with the regions of the RAR ligand binding domains identified to be responsible for the binding of RAR isotype-selectiveligands. Second, we will determine the role of the A domain in mediating ligand binding and anti-API activity of the three RAR isotypes. These studies will involve the creation of several mutant and chimeric RARs and the assay of their affinity for ligand, transactivation activity and anti-API activity.
In Specific Aim 2, we will elucidate the unique role(s) of individual RAR isotypes in RA-dependent regulation of gene expression in F9 teratocarcinoma cells by examining the in vivo binding of RAR isotypes to retinoic acid response elements (RARE) located in the promoter of several target genes. These studies will employ the use of the recently described chromatin immunoprecipitation (ChIP) assay which will allow for the analysis of the direct binding of each RAR isotype to the RARE located in the promoter of specific RA-dependent target genes. PERFORMANCE SITE ========================================Section End===========================================
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