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The proliferation-associated early response gene p22/PRG1 is a novel p53 target gene
H Schäfer1, A Trauzold, T Sebens
11st Department of Medicine, Christian-Albrechts-University of Kiel, Germany.
Abstract:
The novel early response gene p22/PRG1 is linked to cell cycle entry and the induction of proliferation in various cell types although its exact function is still unknown. The p22/PRG1 promoter region contains a 20 bp sequence matching the consensus binding motif for the tumor suppressor protein p53. Gel shift assays demonstrated that p53 specifically binds to an oligonucleotide derived from the p53 binding site of the p22/PRG1 promoter. Chloramphenicol acetyltransferase (CAT) reporter gene assays confirmed that this site confers p53-dependent transcriptional activity to the p22/PRG1 promoter. In Hela cells, p22/PRG1 promoter constructs induced CAT expression only when cotransfected with an expression plasmid for wild-type, but not for mutant p53. Similarly, CAT expression was inducible at the permissive (31 degrees C) but not at the non-permissive temperature (39 degrees C) in the rat embryo fibroblast-derived cell line clone-6 that expresses a temperature-sensitive mutant p53. Conversion of this mutant p53 to a functional p53 at the permissive temperature was accompanied by a significant increase of endogenous p22/PRG1 mRNA level in this cell line. Gamma-irradiation of rat splenocytes or doxorubicin-treatment of Hela cells increased p53 levels followed by transcriptional activation of p22/PRG1 and p21/Waf1 in parallel. Our data demonstrate that p22/PRG1 transcription is induced by p53 during p53-dependent cell cycle arrest and apoptosis. Therefore, p22/PRG1 represents a novel target for transcriptional activation by p53.
Insights
The tumor suppressor protein p53 directly binds to the p22/PRG1 gene promoter, activating its transcription. This study identifies p22/PRG1 as a novel target gene regulated by p53 during cell cycle arrest and apoptosis.
Area of Science:
- Molecular Biology
- Cell Biology
- Cancer Research
Background:
- The early response gene p22/PRG1 is implicated in cell cycle regulation, but its precise function remains unclear.
- The promoter region of p22/PRG1 contains a potential binding site for the tumor suppressor protein p53.
Purpose of the Study:
- To investigate the functional interaction between p53 and the p22/PRG1 gene.
- To determine if p53 regulates p22/PRG1 transcription.
Main Methods:
- Gel shift assays to confirm p53 binding to the p22/PRG1 promoter.
- Chloramphenicol acetyltransferase (CAT) reporter gene assays to assess transcriptional activity.
- Experiments using cell lines with wild-type and temperature-sensitive mutant p53, including treatments with gamma-irradiation and doxorubicin.
Main Results:
- p53 specifically binds to the identified p22/PRG1 promoter sequence.
- The p22/PRG1 promoter confers p53-dependent transcriptional activity.
- p22/PRG1 expression is induced by functional p53 in a dose- and temperature-dependent manner.
- p22/PRG1 transcription is upregulated in parallel with p21/Waf1 following p53 activation by DNA damage.
Conclusions:
- p53 directly activates the transcription of the p22/PRG1 gene.
- p22/PRG1 is a novel target gene of p53-mediated transcriptional regulation.
- p22/PRG1 is involved in p53-dependent cell cycle arrest and apoptosis pathways.