Sp1 and Sp3 activate p21 (WAF1/CIP1) gene transcription in the Caco-2 colon adenocarcinoma cell line

Abstract

The CDK inhibitor p21 WAF1/CIP1 is a negative regulator of the cell cycle, and its expression is induced during terminal dierentiation in vitro and in vivo. Expression of p21 is controlled at the transcriptional level by both p53-dependent and -independent mechanisms. Our previous studies established that p21 is expressed in the Caco-2 adenocarcinoma cell line, and its expression is induced by a p53-independent mechanism during dierentiation of these cells. Here we have found that transcription of p21 in Caco-2 cells is controlled primarily by the transcription factors Sp1 and Sp3 through two Sp1 binding sites, Sp1-1 and Sp1-2, located between 7119 and 7114 bp and between 7109 and 7104 bp of the p21 promoter, respectively. Sp1 and Sp3 binding to the p21 promoter increased during Caco-2 cell dierentiation, while the absolute level of Sp1 did not change and the absolute level of Sp3 increased approximately twofold. Transfection experiments in the SL2 Drosophila cell line that lacks endogenous Sp3 activity demonstrated that Sp1 transactivates the p21 promoter primarily through the Sp1-2 site, while Sp3 acts through the Sp1-1 site. In these cells Sp3 is a stronger transactivator of the p21 promoter than Sp1. Our data suggest that induction of p21 transcription during Caco-2 dierentiation is modulated by Sp1/Sp3 interactions with the p21 promoter. Oncogene (2000) 19, 5182 ± 5188.

Myc represses the p21 (WAF1/CIP1) promoter and interacts with Sp1/Sp3

“…Previously, we found that Sp1 and Sp3 regulate basal transcription of the p21 gene in Caco-2 cells through sequences located between Ϫ119 and ϩ16 bp of the p21 promoter (27), and, here, we show that c-Myc represses the CAT119 construct containing these sequences. c-Myc deletion mutants that retain the ability to associate with Sp1 were able to repress the p21 promoter, suggesting that interactions between Sp1͞Sp3 and c-Myc may be responsible for repression.…”

“…The Caco-2 human colon adenocarcinoma cell line was obtained from the American Type Culture Collection and grown in DMEM͞F12 with 20% FCS. Transfections and CAT assays were performed as described (27).…”

“…In these cells, basal p21 transcription is controlled primarily by the transcription factors Sp1 and Sp3 through the region of the p21 promoter between Ϫ119 and ϩ16 bp that contains six Sp1 binding sites (Fig. 2B) (27). To determine whether c-Myc repression of p21 transcription occurs at the promoter level, we performed transient transfection experiments in Caco-2 cells with different p21-promoter reporters (Fig.…”

Regulation of the CLDN3 gene in ovarian cancer cells

“…On the other hand, CLDN4 gene silencing may involve other mechanisms that are dependent on histone deacetylation (modifications) in addition to MeCP1. While Sp1 typically behaves as an activator and Sp3 as a repressor (as a counterpart of Sp1), [30][31][32] Sp3 can also, in certain cases, act as an activator in cooperation with Sp1, 33,34 indicating that the behavior of Sp3 is promoter-dependent. Therefore, we sought to confirm the roles of Sp1 and Sp3 in CLDN3 promoter regulation using RNAi.…”

Protein kinase C delta inhibits Caco-2 cell proliferation by selective changes in cell cycle and cell death regulators

“…Waf1 expression in Caco-2 cells (Evers et al, 1996;Gartel et al, 1996Gartel et al, , 2000a. Loss of PKC-d in tumorigenesis might, therefore, contribute to the decreased p21…”