Isolation of a Novel Family of C2H2 Zinc Finger Proteins Implicated in Transcriptional Repression Mediated by Chicken Ovalbumin Upstream Promoter Transcription Factor (COUP-TF) Orphan Nuclear Receptors

Abstract

Two novel and related C 2 H 2 zinc finger proteins that are highly expressed in the brain, CTIP1 and CTIP2 (COUP TF-interacting proteins 1 and 2, respectively), were isolated and shown to interact with all members of the chicken ovalbumin upstream promoter transcription factor (COUP-TF) subfamily of orphan nuclear receptors. The interaction of CTIP1 with ARP1 was studied in detail, and CTIP1 was found to harbor two independent ARP1 interaction domains, ID1 and ID2, whereas the putative AF-2 of ARP1 was required for interaction with CTIP1. CTIP1, which exhibited a punctate staining pattern within the nucleus of transfected cells, recruited cotransfected ARP1 to these foci and potentiated ARP1-mediated transcriptional repression of a reporter construct. However, transcriptional repression mediated by ARP1 acting through CTIP1 did not appear to involve recruitment of a trichostatin A-sensitive histone deacetylase(s) to the template, suggesting that this repression pathway may be distinct from that utilized by several other nuclear receptors.COUP-TFI, 1 ARP1/COUP-TFII, and Ear2/COUP-TFIII have been grouped in the same subfamily of orphan nuclear receptors based on sequence similarity (1-3), evolutionary analysis (4), and a common capacity to repress ligand-dependent transcriptional activation of target genes mediated by other nuclear receptors, such as retinoic acid (5-10), thyroid hormone (8), estrogen (11)(12)(13)(14), and vitamin D 3 (9) receptors as well as peroxisome proliferator-activated receptor α (PPARα;Ref. 15).COUP-TFs play important roles in pattern formation in the developing nervous systems of Xenopus (16) and Drosophila (17). Deletion of the COUP-TFI gene in the mouse results in * This work was supported in part by American Heart Association Grant 9640219N; NIEHS, National Institutes of Health, Grants ES00210 and ES00040; the Oregon State University College of Pharmacy; and the Laboratory of Molecular Pharmacology. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.© 2000 by The American Society for Biochemistry and Molecular Biology, Inc. ∥ An established investigator of the American Heart Association. To whom correspondence and reprint requests should be addressed: MATERIALS AND METHODS Yeast Two-hybrid Screening and cDNA CloningYeast two-hybrid screening was conducted as described previously (21) using the hinge region and putative ligand binding domain of ARP1 (amino acids 144-414) as a bait. Fragments corresponding to CTIP1 and CTIP2 (see Fig. 1A) were used to screen mouse cDNA libraries obtained from CLON-TECH and from Dr. René Hen (Columbia University), yielding several overlapping clones. These overlapping clones were then used to prepare a full-length CTIP1 construct that was inserted into the eukaryotic expression vector, pCDNA3+ (Invitrogen). Yeast β-Galactosidase Assays and GST Pull-down ExperimentsProtein-p...

Functional roles for the striatal-enriched transcription factor, Bcl11b, in the control of striatal gene expression and transcriptional dysregulation in Huntington's disease

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