ISOLATION AND CHARACTERIZATION OF THE HUMAN SPR1 GENE AND ITS REGULATION OF EXPRESSION BY PHORBOL ESTER AND CYCLIC-AMP

The small proline-rich protein gene (spr1) is a marker whose expressio n is frequently associated with squamous cell differentiation. We obse rved that the expression of the spr1 gene is strongly induced by phorb ol 12-myristate 13-acetate (PMA). Both the time course result and the nuclear run-on transcriptional assay suggested that the regulation of spr1 expression by PMA is controlled at the transcriptional level. To understand the nature of this regulation, human genomic clones of the spr1 gene were isolated. DNA sequence analysis revealed that the human spr1 gene contains two exons and a single intron located within the 5 '-untranslated region. An AP-1 binding site (TGAGTCA) is found at -142 , and a putative cyclic AMP-responsive element (TGAGGTCA) at -597 base pairs upstream of the transcription start site. A chimeric construct containing the 5'-flanking region of the spr1 gene and the chloramphen icol acetyltransferase (CAT) reporter gene was used to transfect HeLa cells or monkey primary TBE cells. The CAT activity in transfected cel ls is stimulated 7.5-11-fold by PMA, and the stimulation is inhibited by a protein kinase C inhibitor or by pretreating cells with PMA to do wn-regulate the protein kinase C activity. The CAT activity is also st imulated 3.5-fold by dibutyryl cyclic AMP, a protein kinase A activato r. The stimulations by PMA and cAMP are additive. These results sugges t that protein kinase C and probably protein kinase A play important r oles in regulating the transcription of the spr1 gene.