ZIC2 and Sp3 repress Sp1-induced activation of the human D-1A dopamine receptor gene

The human D-1A dopamine receptor is transcribed from a tissue-specific regu lated gene under the control of two promoters. An activator region (AR1) lo cated between nucleotides -1154 and -1136 (relative to the first ATG) enhan ces transcription from the upstream promoter that is active in the brain. I n this investigation, we sought to identify the nuclear factors that regula te the D-1A gene through their binding to AR1 using yeast one-hybrid screen ing. Sp3 and Zic2 were among the positive clones isolated. Although Sp1 was not isolated from this screening and purified Sp1 alone does not bind to A R1 in gel shift experiments, this general transcription factor binds to AR1 in the presence of D-1A expressing NS20Y nuclear extract and activates the D-1A promoter. Thus, Sp1 appears to require an unknown factor(s) or post-t ranslational modification to interact with AR1. On the other hand, Zic2 and Sp3 inhibit Sp1-induced activation of the D-1A gene in an AR1-dependent ma nner. Zic2 and D-1A genes have reciprocal brain regional distributions; Zic 2 is expressed primarily in the cerebellum, and D-1A is highly expressed in corpus striatum. These observations collectively suggest that one of the p hysiologic functions of Zic2 is repression of D-1A gene transcription and t hat the intracellular balance among Sp1, Sp3 and Zic2 is important for regu lating the tissue-specific expression of this dopamine receptor.