ZIC2 and Sp3 Repress Sp1-induced Activation of the HumanD Dopamine Receptor Gene

Abstract

The human D 1A dopamine receptor is transcribed from a tissue-specific regulated gene under the control of two promoters. An activator region (AR1) located between nucleotides ؊1154 and ؊1136 (relative to the first ATG) enhances transcription from the upstream promoter that is active in the brain. In this investigation, we sought to identify the nuclear factors that regulate the D 1A gene through their binding to AR1 using yeast one-hybrid screening. 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 AR1 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-translational 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 manner. Zic2 and D 1A genes have reciprocal brain regional distributions; Zic2 is expressed primarily in the cerebellum, and D 1A is highly expressed in corpus striatum. These observations collectively suggest that one of the physiologic functions of Zic2 is repression of D 1A gene transcription and that the intracellular balance among Sp1, Sp3 and Zic2 is important for regulating the tissuespecific expression of this dopamine receptor.Sp1 and Sp3 are ubiquitous transcription factors that play major roles in the expression of many cellular genes including constitutive housekeeping and inducible genes (1). Sp3 shares extensive structural and sequence homology with Sp1 and can function as a synergist or antagonist of Sp1-mediated activation of target promoters (2-5). In addition, internally translated isoforms of Sp3 function as potent inhibitors of Sp1-mediated transcription in vivo since such truncated isoforms lack substantial portions of the Sp3 transactivation domain (6). Thus, the balance between Sp1 and Sp3 is an important regulator of target genes (7).The murine zinc finger protein of the cerebellum (Zic) was cloned through a search for proteins involved in cerebellar development (8). Subsequently, Zic2 and Zic3 were cloned as members of the Zic gene family (9). Zic expression is highly restricted to the cerebellar granule cell lineage and in medulloblastoma cells (10). Furthermore, analysis of Zic knock-out mice confirms that this transcription factor is involved in cerebellar development (11). On the other hand, mutations in Zic2 have been associated with holoprosencephaly (12). Dopamine plays important roles in several physiologic functions including locomotion (13, 14), learning and memory (15, 16), neuroendocrine modulation (17) We had previously found that the human D 1A receptor gene is transcribed in the brain from two promoters (25). A cis-acting element located between nucleotides Ϫ1154 and Ϫ1136 relative to the translation start site (termed activator region 1, AR1) 1 mediates transactivation of the upstream promoter in neuronal cells (25). ...

Dopamine receptor regulating factor, DRRF: A zinc finger transcription factor

“…4 B-D), DRRF displaces them. Another zinc finger protein Zic2 also can compete with Sp1͞Sp3 binding to their consensus sequence in the D 1A gene and represses Sp1-induced activation of this promoter (12). Furthermore, DRRF represses the D 1A promoter in pCATD1-1197 to a greater extent than the shorter variant in pCATD1-1154.…”

“…(9). Analysis of transcription control mechanisms of D 1A and D 2 genes have revealed a delicate balance among several nuclear factors that tightly regulate expression of these genes (10)(11)(12). For example, the D 2 gene promoter is under strong negative control (13).…”

Sp1 and Sp3 Are Oxidative Stress-Inducible, Antideath Transcription Factors in Cortical Neurons

“…Sp1 is a member of an extended family of DNA-binding proteins that have three zinc finger motifs and bind to guanosine-and cytosine-rich DNA (Briggs et al, 1986;Lania et al, 1997;Suske, 1999;Yang et al, 2000). This family includes members homologous to Sp1, such as Sp2-Sp4.…”

TGFB-induced factor (TGIF): a candidate gene for psychosis on chromosome 18p

“…58 The interplay of a variety of transcription factors like homeoproteins plays an important role in the regulated, tissue-specific and developmental expression of eukaryotic genes. 59 For example, MEIS2, another homeobox protein which activates the Dopamine 1A (D1A) gene promoter in most cells, is in direct competition with TGIF for binding to DNA cisacting factors. TGIF represses MEIS2-induced transcription activation of the D1A receptor; the delicate ratio between MEIS2 and TGIF expression in a given cell type determines the cell-specific expression of the D1A gene.…”