A Novel Human Zinc Finger Protein That Interacts with the Core Promoter Element of a TATA Box-less Gene

Abstract

We describe a novel human cDNA isolated by target site screening of a placental expression library, using as a probe, an essential element of a TATA box-less promoter corresponding to a pregnancy-specific glycoprotein gene. The cDNA encoded a predicted protein of 290 amino acids, designated core promoter-binding protein (CPBP), which has three zinc fingers (type Cys 2 -His 2 ) at the end of its C-terminal domain, a serine/threonine-rich central region and an acidic domain lying within the N-terminal region. Additional sequence analysis and data base searches revealed that only the zinc finger domains are conserved (60 -80% identity) in other transcription factors. In cotransfection assays, CPBP increased the transcription from a minimal promoter containing its natural DNA-binding site. Moreover, a chimeric protein between CPBP and Gal4 DNA binding domain also increased the activity of an heterologous reporter gene containing Gal4 DNA binding sites. The tissue distribution analysis of CPBP mRNA revealed that it is differentially expressed with an apparent enrichment in placental cells. The DNA binding and transcriptional activity of CPBP, in conjunction with its expression pattern, strongly suggests that this protein may participate in the regulation and/or maintenance of the basal expression of PSG and possibly other TATA box-less genes.The molecular mechanisms involved in the transcription of eukaryotic genes are controlled by the ordered interplay of DNA-protein and protein-protein contacts. The factors responsible for basal RNA-polymerase II transcription reaction are the core promoter elements and the general transcription factors (1, 2). In addition, the regulation of transcription rates results from the combined action of activating and repressing proteins that are brought to promoters, enhancers, and silencers through their interactions with specific sequences and sub-

A new role for the Krüppel-like transcription factor KLF6 as an inhibitor of c-Jun proto-oncoprotein function

“…KLF6 mRNA is expressed at basal levels in most tissues and at relatively high levels in human and mice placenta (Koritschoner et al, 1997;Slavin et al, 1999). KLF6 protein expression is detected as two bands of 42 and 46 kDa in several tissues and cells lines (Kojima et al, 2000;Narla et al, 2001, this work) showing different intensity in Western blot assays probably reflecting differences in post-translational modifications.…”

“…The cDNA encoding the complete open reading frame of KLF6 transcription factor (Koritschoner et al, 1997) was cloned into the pXJ, pSG424 and p513-HA expression plasmids to produce wtKLF6 or fused to Gal4-DNA-binding domain or to the hemmagglutinin epitope (HA), respectively (Sadowski et al, 1992). A version devoid of ZF 1-3 (DZF; amino acids 161-289) was also generated in pXJ and p513-HA (Chatton et al, 1995).…”

“…Interestingly, several independent reports described mutations or downregulation of KLF6 gene in human malignancies such as in prostate cancer, astrocytic gliomas, colorectal cancer and non-small-cell lung cancer, thus KLF6 has been proposed as a potential candidate tumor suppressor gene (Narla et al, 2001;Chen et al, 2003;Jeng and Hsu, 2003;Reeves et al, 2004;Ito et al, 2004). Additionally, KLF6 regulates the transcription of several genes such as those encoding the pregnancyspecific glycoprotein 5 (PSG) (Koritschoner et al, 1997), transforming growth factor (TGF)-b1, types I and II TGF-b receptors (Kim et al, 1998), leukotriene C 4 synthase (LTC 4 ) (Zhao et al, 2000), urokinase plasminogen activator (uPA) (Kim et al, 1998) and inducible Nitric Oxide Synthase (Warke et al, 2003), most of which are implicated in proliferation and development of the tissues where they are expressed.…”

“…Protein extracts were prepared and assayed for CAT activity as described previously (Koritschoner et al, 1997). Amounts of cell extracts analysed were normalized to equivalent protein concentration.…”

Regulation of interaction of the acetyltransferase region of p300 and the DNA‐binding domain of Sp1 on and through DNA binding

“…We focused our present studies on the Kru Èppel-like zinc ®nger transcription factors (Ruppert et al 1988) which are a subset of the abundantly found DNA-binding C 2 H 2 -type zinc ®nger factors in eukaryotes (Klug & Schwabe 1995). Exempli®ed by the factors Sp1 (Dynan & Tjian 1983) and GBF (Suzuki et al 1998) (also known as CPBP (Koritschoner et al 1997) and Zf9 (Ratziu et al 1998) but hereafter referred to as GBF), they often bind GC-rich sequences with similar sequence-speci®c binding properties (Sogawa et al 1993;T. Suzuki & M. Horikoshi, unpublished results).…”