Stability of the Sp3-DNA complex is promoter-specific: Sp3 efficiently competes with Sp1 for binding to promoters containing multiple Sp-sites

Center for Molecular Biology of Oral Diseases, College of Dentistry (M/C 860), University of Illinois at Chicago, 801 South Paulina Street, Chicago, IL 60612, USA.
Nucleic Acids Research (Impact Factor: 9.11). 10/2003; 31(18):5368-76. DOI: 10.1093/nar/gkg706
Source: PubMed
The transcription regulatory protein Sp3 shares more than 90% sequence homology with Sp1 in the DNA-binding domain and they bind to the same cognate DNA-element. However, the transcriptional activities of these two Sp-family factors are not equivalent. While Sp1 functions strictly as a transcriptional activator, Sp3 has been shown to be transcriptionally inactive for promoters containing multiple Sp-binding sites. In the present study, we show that the DNA-binding property of Sp3 is promoter dependent and is different from Sp1. The 116 kDa Sp3 polypeptide binds as a monomer to a single Sp-binding site but readily forms slower migrating complexes with adjacent Sp-binding sites. The slower migrating Sp3-DNA complexes are significantly more stable than monomeric Sp3-DNA complexes or multimeric Sp1-DNA complexes. As a consequence, Sp3 can efficiently compete with Sp1 for binding to regions containing multiple Sp sites. The transcription regulatory function of Sp3 is also significantly different from Sp1. Unlike Sp1, Sp3 does not synergistically activate transcription of promoters containing multiple Sp-binding sites. Therefore, although Sp3 is a transcription activator, Sp3 reduces Sp1-dependent transcription of promoters containing adjacent Sp-binding sites by competing with Sp1 for promoter occupancy and thereby blocking the synergistic transactivation function of Sp1. Taken together, this study provides a possible mechanism of the promoter-specific transcription repression function of Sp3.

Full-text preview

Available from:
    • "This suggests that Sp1 and Sp3 are important in the remodeling of chromatin and the regulation of gene expression (Li & Davie, 2010 ). Sp3 represses the Sp1-mediated trans-activation of promoters bearing two or more Sp1-binding sites, yet it does not affect the Sp1-mediated trans-activation of promoters with only one Sp1 site, and Sp3 cannot trans-activate synergistically through two or more Sp1-binding sites (Yu et al., 2003). Sp1 can be modified by phosphorylation, sumoylation, acetylation and glycosylation, while Sp3 modifications include phosphorylation, sumoylation, and acetylation. "
    [Show abstract] [Hide abstract] ABSTRACT: Sp1 (Specificity protein 1) is a well-known member of a family of transcription factors that also includes Sp2, Sp3 and Sp4, which are implicated in an ample variety of essential biological processes and have been proven important in cell growth, differentiation, apoptosis and carcinogenesis. Sp1 activates the transcription of many cellular genes that contain putative CG-rich Sp-binding sites in their promoters. Sp1 and Sp3 proteins bind to similar, if not the same, DNA tracts and compete for binding, thus they can enhance or repress gene expression. Evidences exist that the Sp-family of proteins regulates the expression of genes that play pivotal roles in cell proliferation and metastasis of various tumors. In patients with a variety of cancers, high levels of Sp1 protein are considered a negative prognostic factor. A plethora of compounds can interfere with the trans-activating activities of Sp1 and other Sp proteins on gene expression. Several pathways are involved in the down-regulation of Sp proteins by compounds with different mechanisms of action, which include not only the direct interference with the binding of Sp proteins to their putative DNA binding sites, but also promoting the degradation of Sp protein factors. Down-regulation of Sp transcription factors and Sp1-regulated genes is drug-dependent and it is determined by the cell context. The acknowledgment that several of those compounds are safe enough might accelerate their introduction into clinical usage in patients with tumors that over-express Sp1. Copyright © 2015. Published by Elsevier Inc.
    No preview · Article · May 2015 · Pharmacology [?] Therapeutics
  • Source
    • "In this report, the impact of decline in ARSB on Sp1 in colonic epithelium has been shown using specific inhibitors of Sp1, including Sp1 siRNA and Mithramycin A. Studies to address possible contributions of other SP family members are of interest, since SP transcription factor paralogs, including Sp3 and Sp4, have co-evolved with Sp1, and competition for binding at GC box consensus sites can lead to complex regulatory interactions, particularly involving Sp1 and Sp3505152. The potential interactions between multiple transcriptionally active SP binding sites indicate that intricate, complex regulatory mechanisms are involved53545556. Distinctive properties and effects of Sp4 have also been recognized [57]. "
    [Show abstract] [Hide abstract] ABSTRACT: In cultured human colonic epithelial cells and mouse colonic tissue, exposure to the common food additive carrageenan leads to inflammation, activation of Wnt signaling, increased Wnt9A expression, and decline in the activity of the enzyme arylsulfatase B (ARSB; N-acetylgalactosamine-4-sulfatase). In this study, the novel transcriptional mechanism by which carrageenan and decline in ARSB increase Wnt9A expression in NCM460 and HT-29 human colonic epithelial cells and in mouse colon is presented. Increased expression of Wnt9A has been associated with multiple malignancies, including colon carcinoma, and with ectodermal and mesoendodermal morphogenesis. When ARSB activity was reduced by siRNA or by exposure to carrageenan (1 μg/ml x 24 h), degradation of chondroitin-4-sulfate (C4S) was inhibited, leading to accumulation of more highly sulfated C4S which binds less galectin-3, a β-galactoside binding protein. Nuclear galectin-3 increased and mediated increased binding of Sp1 to the Sp1 consensus sequence in the Wnt9A promoter, shown by oligonucleotide binding assay and by chromatin immunoprecipitation assay. When galectin-3 was silenced, the increases in Sp1 binding to the Wnt9A promoter following carrageenan or ARSB silencing and in Wnt9A expression were inhibited. Mithramycin A, a specific inhibitor of Sp1 oligonucleotide binding, blocked the carrageenan- and ARSB siRNA-induced increases in Wnt9A expression. These studies reveal how carrageenan exposure can lead to transcriptional events in colonic epithelial cells through decline in arylsulfatase B activity, with subsequent impact on C4S, galectin-3, Sp1, and Wnt9A and can exert significant effects on Wnt-initiated signaling and related vital cell processes.
    Full-text · Article · Apr 2014 · Journal of Biological Chemistry
  • Source
    • "Interestingly, Sp1 is a known transcriptional activator [36], [37] but Sp3 can act either as a transcriptional activator or repressor [38]. For example, Sp3 can competes the GC-box binding with Sp1 resulting in negative regulation of the promoter [39]–[42]. "
    [Show abstract] [Hide abstract] ABSTRACT: Although structurally and biochemically similar to the cellular prion (PrP(C)), doppel (Dpl) is unique in its biological functions. There are no reports about any neurodegenerative diseases induced by Dpl. However the artificial expression of Dpl in the PrP-deficient mouse brain causes ataxia with Purkinje cell death. Abundant Dpl proteins have been found in testis and depletion of the Dpl gene (Prnd) causes male infertility. Therefore, we hypothesize different regulations of Prnd in the nerve and male productive systems. In this study, by electrophoretic mobility shift assays we have determined that two different sets of transcription factors are involved in regulation of the Prnd promoter in mouse neuronal N2a and GC-1 spermatogenic (spg) cells, i.e., upstream stimulatory factors (USF) in both cells, Brn-3 and Sp1 in GC-1 spg cells, and Sp3 in N2a cells, leading to the expression of Dpl in GC-1 spg but not in N2a cells. We have further defined that, in N2a cells, Dpl induces oxidative stress and apoptosis, which stimulate ataxia-telangiectasia mutated (ATM)-modulating bindings of transcription factors, p53 and p21, to Prnp promoter, resulting the PrP(C) elevation for counteraction of the Dpl cytotoxicity; in contrast, in GC-1 spg cells, phosphorylation of p21 and N-terminal truncated PrP may play roles in the control of Dpl-induced apoptosis, which may benefit the physiological function of Dpl in the male reproduction system.
    Full-text · Article · Dec 2013 · PLoS ONE
Show more