REGULATION OF SALIVARY-GLAND-SPECIFIC GENE-EXPRESSION

The results from in vivo transgenic and in vitro transfection studies designed to identify cis-element(s) and trans-factor(s) governing the salivary proline-rich proteins (PRPs), amylase, and parotid secretory protein (PSP) gene expression are utilized as a paradigm to discuss th e regulation of salivary-specific gene expression. Particular attentio n is given to the molecular mechanism(s) underlying the salivary PRP R 15 gene regulation. In rodents, the PRPs are selectively expressed in the acinar cells of salivary glands, and are inducible by the beta-ago nist isoproterenol and by dietary tannins: The results from a series o f experiments using chimeric reporter constructs containing different lengths of the R15 distal enhancer region, their mutations, and variou s expressing constructs are analyzed and discussed, These data suggest that the inducible nuclear orphan receptor NGFI-B may participate in the regulation of salivary acinar-cell-specific and inducible expressi on of the rat R15 gene via three distinct distal NGFI-B sites. Taken t ogether, a model for the induction of R15 gene expression by lpr is pr oposed. However, the exact molecular basis of this NGFI-B-mediated tra nsactivation of cAMP-regulated R15 expression remains to he establishe d.