Involvement of Negative Cofactor NC2 in Active Repression by Zinc Finger-Homeodomain Transcription Factor AREB6

Abstract

The transcription factor AREB6 contains a homeodomain flanked by two clusters of Krüppel type C 2 H 2 zinc fingers. AREB6 binds to the E-box consensus sequence, CACCTGT, through either the N-or the C-terminal zinc finger cluster. To gain insights into the molecular mechanism by which AREB6 activates and represses gene expression, we analyzed the domain structure of AREB6 in the context of a heterologous DNA-binding domain by transient-transfection assays. The C-terminal region spanning amino acids 1011 to 1124 was identified as a conventional acidic activation domain. The region containing amino acids 754 to 901, which was identified as a repression domain, consists of 40% hydrophobic amino acids displaying no sequence similarities to other known repression domains. This region repressed transcription in vitro in a HeLa nuclear extract but not in reconstituted transcription systems consisting of transcription factor IID (TFIID), TFIIB, TFIIE, TFIIH/F, and RNA polymerase II. The addition of recombinant negative cofactor NC2 (NC2␣/DRAP1 and NC2␤/Dr1) to the reconstituted transcription system restored the activity of the AREB6 repression domain. We further demonstrated interactions between the AREB6 repression domain and NC2␣ in yeast two-hybrid assay. Our findings suggest a mechanism of transcriptional repression that is mediated by the general cofactor NC2.

p53-Mediated Repression of Alpha-Fetoprotein Gene Expression by Specific DNA Binding

“…p53-mediated activation of AFP expression in NIH 3T3 cells which lack HNF-3 argues against recruitment of ubiquitous, general repressors of transcription by p53 binding. This mode of transcription repression has been described for general transcription repressor NC2 tethering via DNA-bound AREB6 Zn-finger/homeodomain protein (41). However, our results indicate that repression of AFP may involve tissue-specific corepressors of transcription that are targeted by p53 binding within the developmental repressor domain.…”

Novel mutations in theZEB1 gene identified in Czech and British patients with posterior polymorphous corneal dystrophy

“…It has recently been reported that changes within the ZEB1 gene are responsible for the pathogenesis in a large percentage of patients with this corneal disorder (Krafchak, et al, 2005). ZEB1 maps to chromosome 10p11.2, comprises 9 exons and encodes a transcription factor that is organized in multiple functional domains starting with N-terminal zinc finger clusters (172-292), followed by a homeodomain (581-640), repression domain (754-901), C-terminal zinc finger clusters (905-981) and acidic activation domain (1011-1124) (Ikeda, et al, 1998). We have identified four novel disease mutations within the ZEB1 gene in subjects with PPCD, in four of ten unrelated PPCD families.…”

Orchestrated response: a symphony of transcription factors for gene control

“…Class IV co-factors include those that covalently modify nucleosomes. Members of this class are represented here by the histone acetylases CBP/p300, GCN5, P/CAF, and the SRC-1-related p160 family Yang et al 1996;Grant et al 1997;Spencer et al 1997), as well as the histone deacetylases HDAC-1 and HDAC-2 (rpd3), and Chen et al 1994;Ge and Roeder 1994;Sun et al 1994;Yokomori et al 1994;Chi et al 1995;Hansen and Tjian 1995;Verrijzer et al 1995;Dikstein et al 1996a;Mermelstein et al 1996;Mizzen et al 1996;Brandsen et al 1997;Ikeda et al 1998;Malik et al 1998). b (Triezenberg et al 1988;Liu and Green 1990;Wilson et al 1993;Jarriault et al 1995;Luo and Roeder 1995;Strubin et al 1995;Jimenez et al 1997;Nibu et al 1998;.…”