RESUMO
Promoter of the Prnd gene coding for the Prion-like protein Doppel contains two critical cis-regulatory elements, NF-Y consensus motif and canonical E-box. Here, we studied a role of the upstream stimulatory factor (USF) in the E-box-mediated activation of Prnd transcription. Co-expression of USF-1 with the luciferase reporter gene driven by the -185/+27 Prnd promoter fragment resulted in several fold increase of the luciferase activity. Conversely, mutations within the E-box led to a significantly reduced Prnd promoter activation. USF-1 binding was supported by the gel shift assay, supershift with USF-1 antibody and UV cross-linking. The activation capacity of the related USF-2, c-Myc and HIF-2alpha proteins was lower compared to USF-1 suggesting that USF-1 is the major E-box-binding transcription factor regulating the Prnd promoter.
Assuntos
Regulação da Expressão Gênica , Príons/genética , Fatores Estimuladores Upstream/genética , Animais , Células Cultivadas , Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/metabolismo , Elementos E-Box/genética , Ensaio de Desvio de Mobilidade Eletroforética , Proteínas Ligadas por GPI , Genes Reporter , Camundongos , Mutação , Príons/metabolismo , Regiões Promotoras Genéticas , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo , Transcrição Gênica , Fatores Estimuladores Upstream/metabolismoRESUMO
Transcription of the CA9 gene coding for a tumor-associated carbonic anhydrase IX (CA IX) isoform is regulated by hypoxia via the hypoxia-inducible factor 1 (HIF-1) and by high cell density via the phosphatidylinositol-3-kinase (PI3K) pathway. We examined the role of the mitogen-activated protein kinase (MAPK) pathway in the control of CA9 gene expression. Inhibition of MAPK signaling by U0126 in HeLa cells led to reduced activity of the PR1-HRE-luc CA9 promoter construct and decreased CA IX protein levels in dense culture as well as in hypoxia. Similar reduction was obtained by expression of a dominant-negative ERK1 mutant and was also observed in U0126-treated HIF-1alpha-deficient Ka13 cells. Simultaneous treatment with the MAPK and PI3K inhibitors U0126 and LY 294002 had stronger effect than individual inhibition of these pathways. Taken together, our results suggest that besides the PI3K pathway, the MAPK cascade is involved in the regulation of CA9 gene expression under both hypoxia and high cell density.
