Regulation of renin enhancer activity by nuclear factor I and Sp1/Sp3.
Transcription of the mouse Ren-1(c) gene in kidney tumor-derived As4.1 cells, which express high levels of renin mRNA, is dependent on a proximal promoter element and a 242-bp enhancer region located 2.6 kb upstream of the transcription start site. We showed previously that the enhancer contains a cAMP responsive element (CRE) and an E-box. Mutation of either element resulted in almost complete loss of the Ren-1(c) expression. In this report we show that there are additional transcription factor-binding sites within the Ren-1(c) enhancer contributing to the enhancer activity. Electrophoretic mobility shift and supershift assays have identified four nuclear factor I (NFI)-binding sites, an Sp1/Sp3 site and an unidentified transcription factor-binding site (Ei) located upstream of the CRE and E-box. Mutation of the Sp1/Sp3 site or Ei reduced Ren-1(c) expression by 40% or 30%, respectively, while mutations of four NFI-binding sites resulted in an 89% decrease in expression. Thus, these protein-DNA interaction sites are essential for transcription of mouse renin genes. There are four homologous NFI genes ( NFI-A, -B, -C and -X) in vertebrates and multiple alternatively spliced isoforms from each gene. Real-time reverse transcriptase-polymerase chain reaction (RT-PCR) assays have demonstrated that NFI-X is the predominant NFI mRNA expressed in As4.1 cells. Direct study of involvement of NFI-X in regulation of renin genes is underway.[1]References
- Regulation of renin enhancer activity by nuclear factor I and Sp1/Sp3. Pan, L., Glenn, S.T., Jones, C.A., Gronostajski, R.M., Gross, K.W. Biochim. Biophys. Acta (2003) [Pubmed]
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