Transcription Factors Ets1, NF-κB, and Sp1 Are Major Determinants of the Promoter Activity of the Human Protein Kinase CK2α Gene

Abstract

CK2␣ is one of two isoforms of protein kinase CK2, a highly conserved, ubiquitous, and vital phosphotransferase whose expression is kept at constant cellular levels and whose dysregulated expression has been linked to malignant diseases. The upstream sequence of the gene coding for human CK2␣ (CSNK1A1, chromosomal location 20p13) has been examined for promoter location and transcription factor interactions using reporter gene assays (luciferase; HeLa cells), site-directed mutagenesis, electrophoretic mobility shift assays, super-shifts, UV cross-linking, Western blotting, and DNA affinity chromatography. Highest promoter activity has been found in a region comprising positions ؊9 to 46. Factors Sp1, Ets-1, and NF-B have been identified as interaction partners and, by mutation of individual sites and simultaneous mutations of two or more sites, shown to cross-talk to each other. At least two of the factors (Sp1; NF-B) were susceptible to phosphorylation by CK2 holoenzyme, a tetramer composed of two CK2␣ and two regulatory CK2␤ proteins, but not by individual CK2␣. Because the phosphorylation decreases promoter binding and repeated immunoprecipitation reveals presence of "free" CK2␤ in cell extracts, it is tempting to speculate that the gene product CK2␣ might readily form CK2 holoenzyme and feed back onto gene transcription. The data represent the first promoter control analysis of a mammalian CK2␣ gene and provide a hypothesis of how the constant expression level of CK2␣ may be achieved. Protein kinase CK21 (also named casein kinase II) is a pleiotropic, ubiquitous, and conserved Ser/Thr kinase that is essential for viability of eukaryotes. CK2 occurs in two highly related isoforms, CK2␣ and CK2␣Ј. Both of these occur as tetrameric holoenzymes complexed stoichiometrically to regulatory CK2␤ proteins. This tetrameric structure is also highly conserved and required for appropriate control of substrate specificity. Although a considerable number of substrates has been documented, comprising proteins involved in processes such as transcription, replication, translation, and signaling, the exact physiological role of CK2 remains poorly understood. However, CK2 has been linked to proliferation, transformation, and cell cycle regulation (reviewed in Refs.

The Sp1 transcription factor contributes to the tumor necrosis factor-induced expression of the angiogenic factor thymidine phosphorylase in human colon carcinoma cells

“…Response elements that were not found by sequence analysis in the 1.4-kb 5'-region of the TP gene included AP1, NF-kB, HIF1 and Egr1. In addition to their individual roles in regulating transcription, reports suggest that there is cross-talk between transcription factors, including evidence that gene activation by Sp1 can be modulated by positive and negative interactions with other transcription factors (Hirano et al, 1998;Krehan et al, 2000;Cakouros et al, 2001). Experiments with constructs containing 5'-truncations of the TP promoter revealed that the transcriptional activity dramatically decreased with deletion of sequence spanning 7368 to 7155 and 7155 to 764.…”

Regulation of Ets function by protein–protein interactions

“…Similarly, it is known that Rb, which interacts with Elf1, physically interacts with histone deacetylase HDAC1 (MagnaghiJaulin et al, 1998). Another example is Sp1, which interacts with many Ets factors (Block et al, 1996;Dittmer et al, 1997;Eichbaum et al, 1997;Krehan et al, 2000)), and has been shown to interact with HDAC1 (Doetzlhofer et al, 1999), repressing transcription. TEL is able to recruit co-repressors such as SMRT and mSin3A resulting in transcriptional repression Fenrick et al, 1999).…”

“…Adjacent or overlapping binding sites for Ets and NFkB are present in many inducible lymphoid genes, including IL-2, IL2-receptor (John et al, 1995), IL-3 (Gottschalk et al, 1993), GM-CSF (Thomas et al, 1997), IL-12 (Gri et al, 1998), viral genes including the HIV-I enhancer (Seth et al, 1993) and signaling molecules, such as protein kinase CK2a (Krehan et al, 2000). Co-transfection of NFkB and Ets contributes to synergistic transcription activation of HIV-I and HIV-II , GM-CSF (Thomas et al, 1997), IL-2Ra (John et al, 1995) and IL-12 (Gri et al, 1998).…”

Sp1 Transcriptional Activity Is Up-regulated by Phosphatase 2A in Dividing T Lymphocytes

“…It is of interest that cyclin D1 and retinoblastoma protein modulate Sp1 cross-talk with the basal transcriptional machinery through their direct association with the TATA-box-associated protein TAF II 250 (15,22). Second, Sp1 exerts its transcriptional activation with the help of a growing list of inducible specific transcription factors such as nuclear factor-B (23,24) and Stat (25,26), as well as with co-modulators (see Ref. 27 for review) such as Smad family factors (28), CBP/p300 (29,30), and the cofactor required for Sp1 activation multiprotein complex (31).…”