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The human tumour suppressor gene p53 is alternatively spliced in normal cells
J M Flaman1, F Waridel, A Estreicher
1Laboratoire de Génétique Moléculaire, CHU de Rouen, France.
Abstract:
Alternative splicing affecting the p53 carboxy-terminus has previously been described in mouse but not in normal human cells. We report here the detection in normal human lymphocytes of an alternatively spliced form of human p53 mRNA containing an additional 133 bp exon derived from intron 9. This splice variant encodes a truncated protein of 341 amino-acids including 10 new amino-acids derived from the novel exon. The truncated protein, which lacks part of the p53 tetramerization domain, fails to bind DNA in vitro and has a transcriptional defect in vivo in both yeast and mammalian cells. Quantitative RT-PCR experiments suggest that the alternatively spliced form is only present in significant amounts in quiescent cells. Considering the numerous functions ascribed to the carboxy-terminus of the p53 protein, this splice variant may have important implications for the biological role of p53 in normal cells.
Insights
Researchers discovered a new human p53 splice variant in lymphocytes. This variant produces a truncated protein, impacting DNA binding and transcriptional activity, particularly in quiescent cells.
Area of Science:
- Molecular Biology
- Genetics
- Cell Biology
Background:
- Alternative splicing of p53 carboxy-terminus is known in mice.
- This phenomenon was not previously documented in normal human cells.
Purpose of the Study:
- To identify and characterize alternatively spliced forms of human p53 mRNA in normal human cells.
- To investigate the functional consequences of any novel splice variants found.
Main Methods:
- Detection of alternatively spliced p53 mRNA using RT-PCR in normal human lymphocytes.
- Analysis of the encoded protein's structure and function (DNA binding, transcriptional activity).
Main Results:
- A novel alternatively spliced human p53 mRNA variant was detected in normal lymphocytes, containing an extra exon from intron 9.
- This variant encodes a truncated p53 protein (341 amino acids) lacking part of the tetramerization domain.
- The truncated protein exhibits impaired in vitro DNA binding and in vivo transcriptional defects in yeast and mammalian cells.
- The splice variant is predominantly found in quiescent cells.
Conclusions:
- A novel p53 splice variant exists in normal human cells, specifically in lymphocytes.
- This variant produces a non-functional truncated protein, affecting p53's role in DNA binding and transcription.
- The variant's prevalence in quiescent cells suggests a potential role in regulating p53 activity in this cellular state.