UPSTREAM ELEMENTS INVOLVED IN-VIVO IN ACTIVATION OF THE BRAIN-SPECIFIC RAT ALDOLASE-C GENE - ROLE OF BINDING-SITES FOR POU AND WINGED HELIXPROTEINS

The rat aldolase C gene encodes a glycolytic enzyme strongly expressed in adult brain. We previously reported that a 115-base pair (bp) prom oter fragment was able to ensure the brain-specific expression of the chloramphenicol acetyltransferase (CAT) reporter gene in transgenic mi ce, but only at a low level (Thomas, M., Makeh, I., Briand, P., Kahn, A, and Skala, H. (1993) fur. J. Biochem. 218, 143-151). Here we show t hat in vivo activation of this promoter at a high level requires coope ration between an upstream 0.6-kilobase pair (kb) fragment and far ups tream sequences. In the 0.6-kb region, a 28-bp DNA element is shown to include overlapping in vitro binding sites for POU domain regulatory proteins and for the Winged Helix hepatocyte nuclear factor-3 beta fac tor. An hepatocyte nuclear factor-3 beta-binding site previously descr ibed in the short proximal promoter fragment is also shown to interact in vitro with POU proteins, although with a lower affinity than the 2 8-bp motif. Additional binding sites for POU factors were detected in the upstream 0.6-kb sequences. Progressive deletion in this region res ulted in decreased expression levels of the transgenes in mice, sugges ting synergistic interactions between these multiple POU-binding sites . We propose that DNA elements characterized by a dual binding specifi city for both POU domain and Winged Helix transcription factors could play an essential role in the brain-specific expression of the aldolas e C gene and other neuronal genes.