ARPP-21 - MURINE GENE STRUCTURE AND PROMOTER IDENTIFICATION OF A NEURONAL PHOSPHOPROTEIN ENRICHED IN THE LIMBIC STRIATUM

ARPP-21 (cAMP-regulated phosphoprotein, M(r)=21,000 on sodium dodecyl sulfate polyacrylamide gel electrophoresis) is a phosphoprotein highly enriched in concentration in the neurons of the limbic striatum. It i s likely a third messenger in the intracellular cascade of events foll owing neuronal stimulation by first-messenger activators of the adenyl ate cyclase system, including dopamine via the D-1 receptor. ARPP-21 e xpression is restricted to telencephalic post-mitotic, post-migrationa l neurons, and its precise pattern of temporal and spatial expression makes it an attractive candidate for the study of transcriptional regu lation of neuronal maturation. To define genomic regions likely to con tain functional promoter elements, we isolated the murine ARPP-21 gene . Primer extension and T2 RNase protection analyses identified multipl e transcription start sites, but 1.3 kb of 5'-flanking DNA revealed fe w consensus transcription factor binding sequences. A series of transi ent transfection assays in clonal cell lines which do not express ARPP -21 identified a basal promoter active in both neuronal and non-neuron al lines. Expression in all lines was decreased by the inclusion of re gions further upstream, and extinguished by the inclusion of the first intron. Further analyses are likely to reveal cell specific regulator y sequences.