The long term objectives of the research outlined by this proposal are (1) to understand why the expression of a given set of gene (proline-rich protein genes) is limited to the salivary glands; and (2) to determine how this expression is modulated in response to regulatory input from beta- agonist, isoproterenol. An understanding of the activation of tissue- specific gene expression is not only of fundamental biological interest but also of practical importance in implementing genetic engineering and possibly gene therapy.
Specific aims i nclude (i) identifying cis-acting element(s) located on the 5'-flanking region and/or within the proline-rich protein transcriptional unit that is responsible for regulating tissue- specific and accurate transcription; (ii) completing the structural characterization and physical linkage of the rat tissue-specific proline- rich protein multigene family and cloning at least one monkey proline-rich protein gene; and (iii) detecting and characterizing nuclear proteins that interact with the cis-regulatory elements identified in specific aim (i). The unique appearance of proline-rich proteins in human and monkey saliva at high level suggests functional role(s) in the oral cavity or elsewhere. Of special importance is the dramatic induction of proline-rich proteins in the salivary glands by beta-agonist, isoproterenol, as demonstrated in rodents. Feeding tannins induces the same gene expression as isoproterenol in rats and mice but not in hamsters which show an unusual growth inhibition by tannins. This suggests that the induction of proline-rich proteins by tannins or other polyphenols protects the animals from the detrimental effects of tannins on nutrition and weight gain. The populations that consume high-tannin foods or chew betel nuts have a high incidence of oral and esophageal cancer. Proline-rich proteins have high affinity for tannins, and these unusual proteins may be beneficial to both rodents and higher primates. The general methods to be used include cloning, recombinant DNA techniques, DNA sequencing, cell transfections, mini-gene construction and gene induction and activation analyses, pulsed field gel electrophoresis mapping, and methods involved in the identification and characterization of trans-acting factors.
