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Mouse p53 inhibits SV40 origin-dependent DNA replication
A W Braithwaite1, H W Sturzbecher, C Addison
1Marie Curie Research Institute, Surrey, UK.
Abstract:
p53 is a cellular phosphoprotein that is present at elevated concentrations in cells transformed by different agents. p53 complementary DNA expression-constructs immortalize primary cells in vitro and co-operate with an activated ras oncogene in malignant transformation. Several reports have implicated p53 in mammalian cell cycle control and specifically with events occurring at the G0-G1 boundary. p53 forms specific complexes with simian virus 40 (SV40) large-T antigen, and such complexes are found associated with both replicating and mature SV40 DNA in lytically infected cells. In an accompanying paper Gannon and Lane report that in in vitro plate-binding assays, mouse p53 can displace polymerase alpha from complex with T-antigen. We have examined the in vivo consequences of expressing wild-type and mutant p53 proteins from other species in SV40-transformed monkey cells. We report here that expression of mouse p53 results in a substantial and selective inhibition of SV40 origin-dependent DNA replication. In addition to any function in the G0-G1 transition, the data presented suggest that p53 may affect directly the initiation or maintenance of replicative DNA synthesis.
Insights
The tumor suppressor protein p53, when expressed in monkey cells, significantly inhibits simian virus 40 (SV40) DNA replication. This finding suggests p53 plays a direct role in regulating DNA synthesis initiation and maintenance.
Area of Science:
- Molecular Biology
- Virology
- Cell Biology
Background:
- p53 is a phosphoprotein elevated in transformed cells.
- p53 is implicated in cell cycle control, particularly at the G0-G1 phase.
- p53 forms complexes with SV40 large-T antigen.
Purpose of the Study:
- To investigate the in vivo effects of expressing wild-type and mutant p53 proteins from different species in SV40-transformed monkey cells.
- To determine if p53 influences SV40 DNA replication.
Main Methods:
- Expression of mouse p53 in SV40-transformed monkey cells.
- Assessing SV40 origin-dependent DNA replication.
- Analysis of p53 interactions with SV40 large-T antigen.
Main Results:
- Expression of mouse p53 substantially and selectively inhibited SV40 origin-dependent DNA replication.
- p53's inhibitory effect on DNA replication was observed in vivo.
- Data suggest p53 may directly impact the initiation or maintenance of replicative DNA synthesis.
Conclusions:
- p53 can directly inhibit SV40 DNA replication.
- Beyond its role in cell cycle control, p53 appears to regulate DNA synthesis.
- These findings contribute to understanding p53's function in viral DNA replication and cellular processes.