REGULATION OF SALIVARY GLAND-SPECIFIC GENE EXPRESSION

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Salivary proteins play a crucial role in protecting the hard and soft tissues of the mouth from disease. Unfortunately, little is known about the basic molecular events which regulate the synthesis of salivary gland-specific proteins. Thus, the long term goal of this program is to define the mechanisms which regulate salivary gland-specific gene expression. We have chosen as a model the gene which encodes the rat salivary glutamine/glutamic acid-rich protein-Ca (GRP-Ca), which is a member of the superfamily of proline-rich proteins. Compelling evidence points to the importance of transcriptional control in regulating the expression of tissue-specific gene products. We hypothesize that there is a set of unique cis-acting elements and transcription factors which are responsible for the expression of GRP-Ca. To test this hypothesis we propose to: (1) functionally map the cis- acting elements of the GRP-Ca gene using transgenic mice and cell lines of salivary gland and non-salivary gland origin, and (2) identify salivary gland nuclear proteins which interact with these cis-acting elements by mobility shift and DNase I foot-printing assays. These salivary gland DNA binding proteins will be purified by combinations of ion-exchange and oligonucleotide-affinity chromatography. Superimposed over the level of gene regulation afforded by the interaction of transcription factors with their cognate cis-acting elements are the mechanisms which regulate the expression of the transcription factors themselves. In salivary glands we hypothesize that transcription factor expression is controlled, in part, by secretagogues, thereby coupling exocytosis and protein biosynthesis. To test this hypothesis, we propose to measure the effect of the secretagogue isoproterenol on the transcription of the GRP-Ca gene by performing nuclear run-off assays. In addition, we will determine if isoproterenol influences the stability of the GRP-Ca transcript. Collectively, our studies will provide the fundamental information required to begin development of novel gene therapy approaches for the treatment of salivary gland hypofunction.