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p53-catalyzed annealing of complementary single-stranded nucleic acids
P Oberosler1, P Hloch, U Ramsperger
1Fakultät für Biologie, Universität Konstanz, Germany.
Abstract:
p53 has been reported to inhibit the DNA helicase intrinsic to simian virus 40 large tumor antigen (T antigen). We found that inhibition is not restricted to T antigen, but also affects several other DNA and RNA helicases. Complexing of the helicases by the p53 protein as a possible inactivation mechanism could be excluded. Instead, the anti-helicase activity can be explained by our finding that p53 binds with high affinity to single-stranded nucleic acids and has a strong DNA.DNA and RNA.RNA annealing activity. We could also show that p53 is able to alter the secondary structure of RNA and/or to influence dynamic RNA-RNA interactions. These results, and the fact that the affinity of p53 to RNA is about one order of magnitude higher than to single-stranded DNA, imply an RNA-specific function of p53 in vivo.
Insights
The tumor suppressor p53 protein inhibits DNA and RNA helicases by binding to single-stranded nucleic acids, not by complexing. This suggests a specific RNA-related function for p53 in vivo.
Area of Science:
- Molecular Biology
- Virology
- Biochemistry
Background:
- The p53 protein is known to inhibit the DNA helicase activity of simian virus 40 large tumor antigen (T antigen).
- The precise mechanism by which p53 interacts with and affects helicase function remains incompletely understood.
Purpose of the Study:
- To investigate the interaction of p53 with various DNA and RNA helicases beyond simian virus 40 T antigen.
- To elucidate the mechanism underlying p53's anti-helicase activity.
Main Methods:
- Assays to test the effect of p53 on multiple DNA and RNA helicases.
- Analysis of p53's binding affinity to single-stranded DNA and RNA.
- Investigation of p53's nucleic acid annealing and secondary structure alteration capabilities.
Main Results:
- p53 inhibits multiple DNA and RNA helicases, not exclusively simian virus 40 T antigen.
- p53's anti-helicase activity is mediated by high-affinity binding to single-stranded nucleic acids and potent DNA:DNA and RNA:RNA annealing activity.
- p53 alters RNA secondary structure and influences RNA-RNA interactions, with a significantly higher affinity for RNA than for single-stranded DNA.
Conclusions:
- The anti-helicase activity of p53 is not due to direct complexation and inactivation of the enzymes.
- p53's strong nucleic acid binding and annealing activities explain its inhibitory effects on helicases.
- The higher affinity of p53 for RNA suggests a specific, potentially RNA-centric, biological role in vivo.