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Binding of Sp1 and Sp3 transcription factors to the Oct-4 gene promoter
M Pesce1, M Marin Gomez, S Philipsen
1Gene Expression Programme, Germ Cell Biology Group, European Molecular Biology Laboratory, Heidelberg, Germany. m.pesce@med.uniroma2.it
Abstract:
Oct-4 is expressed in embryonic stem cells and is one of the first transcription factors differentially regulated during mouse development. Recent ablation of Oct-4 function in vivo has demonstrated that its expression is essential for preventing embryonic cell differentiation. Several studies have indicated that activation of the Oct-4 TATA-less promoter is mediated by a GC-box representing a high affinity binding site for the transcription factor Sp1. In this study, we have analyzed Oct-4 expression and the activity of the Oct-4 promoter GC box in Sp1 deficient ES cells. We found that in these cells, Oct-4 RNA and protein levels were comparable to wt ES cells and the activity of the Oct-4 promoter GC-box was even increased. Furthermore, the pattern of Oct-4 down-regulation in Sp1 deficient ES cells was unchanged compared to wt cells. Analysis of GC-box binding proteins in extracts from Sp1-/- ES cells revealed that Sp3, another member of the Sp1 transcription factors family, efficiently bound to Sp1 site. These results show that in ES cells Sp1 is not essential for Oct-4 gene activity. Thus, Sp1 function in undifferentiated embryonic cells may be complemented by Sp3 and/or by other GC-box binding transcription factors.
Insights
Transcription factor Sp1 is not essential for Oct-4 gene activity in embryonic stem cells. Sp3 or other factors may compensate for Sp1 function, maintaining Oct-4 expression and preventing differentiation.
Area of Science:
- Developmental Biology
- Stem Cell Biology
- Molecular Genetics
Background:
- Oct-4 is crucial for maintaining embryonic stem cell pluripotency and preventing differentiation.
- The Oct-4 promoter's GC-box is a key regulatory element, often bound by transcription factor Sp1.
Purpose of the Study:
- To investigate the role of Sp1 in regulating Oct-4 expression and promoter activity in embryonic stem cells.
- To determine if Sp1 deficiency affects Oct-4 levels or its promoter's GC-box activity.
Main Methods:
- Analysis of Oct-4 RNA and protein levels in Sp1-deficient (Sp1-/-) and wild-type (wt) embryonic stem cells.
- Assay of Oct-4 promoter GC-box activity in Sp1-/- ES cells.
- Identification of GC-box binding proteins in Sp1-/- ES cell extracts.
Main Results:
- Oct-4 RNA and protein levels were comparable in Sp1-/- and wt ES cells.
- Oct-4 promoter GC-box activity was increased in Sp1-/- ES cells.
- Sp3, a related transcription factor, was found to bind the Sp1 site in Sp1-/- ES cells.
Conclusions:
- Sp1 is not essential for Oct-4 gene activity in embryonic stem cells.
- Sp3 or other GC-box binding factors can compensate for Sp1 function in maintaining Oct-4 expression in undifferentiated cells.