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Inactivation of p53 gene expression by an insertion of Moloney murine leukemia virus-like DNA sequences
Abstract:
Analysis of Abelson murine leukemia virus-transformed L12 cells which lack the p53 cellular encoded tumor antigen revealed alterations in the p53-specific genomic DNA sequences. The active p53 gene, usually contained in a 16-kilobase EcoRI DNA fragment of p53 producer cells, went through major alterations leading to the appearance of a substantially larger 28.0-kilobase p53-specific EcoRI fragment. Detailed restriction enzyme analysis, with genomic probes spanning throughout the whole active p53 gene, indicated that the L12 p53 altered gene contains all the exons and principal introns of the normal p53 16.0-kilobase gene. However, its structure was interrupted by the integration of a novel DNA segment into the noncoding intervening sequences of the first p53 intron. Analysis of the inserted sequences revealed close homology to Moloney murine leukemia virus. This Moloney leukemia murine virus-like particle resides in a 5' to 3' transcriptional orientation, similar to the p53 gene, permitting the transcription of aberrant fused mRNA molecules detected in these cells.
Insights
Abelson murine leukemia virus transformed cells showed altered p53 gene sequences. A Moloney murine leukemia virus DNA segment integrated into the p53 gene, causing aberrant mRNA production.
Area of Science:
- Molecular Biology
- Virology
- Oncology
Background:
- The p53 tumor suppressor gene is crucial for cellular integrity and cancer prevention.
- Abelson murine leukemia virus (A-MuLV) transformation can disrupt normal cellular processes.
- L12 cells, transformed by A-MuLV, lack functional p53 protein.
Purpose of the Study:
- To investigate the genomic alterations of the p53 gene in A-MuLV-transformed L12 cells.
- To identify the molecular mechanisms underlying the loss of p53 function in these cells.
Main Methods:
- Restriction enzyme analysis of genomic DNA.
- Hybridization with genomic probes specific to the p53 gene.
- Analysis of inserted DNA sequences and their homology.
- Detection of aberrant mRNA transcripts.
Main Results:
- L12 cells exhibited a significantly larger 28.0-kilobase EcoRI DNA fragment containing the p53 gene, compared to the normal 16-kilobase fragment.
- The altered p53 gene structure in L12 cells included an insertion of a DNA segment homologous to Moloney murine leukemia virus (M-MuLV).
- This M-MuLV-like insertion occurred within the first intron of the p53 gene, in a 5' to 3' transcriptional orientation.
- Aberrant fused mRNA molecules transcribed from the disrupted p53 gene were detected in L12 cells.
Conclusions:
- The integration of an M-MuLV-like DNA sequence into the p53 gene is responsible for the observed genomic alterations in L12 cells.
- This viral DNA integration disrupts the normal structure and transcription of the p53 gene, leading to the production of non-functional mRNA.
- These findings elucidate a novel mechanism of p53 inactivation by viral integration in leukemia virus-transformed cells.