P53-CATALYZED ANNEALING OF COMPLEMENTARY SINGLE-STRANDED NUCLEIC-ACIDS

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 RN A helicases. Complexing of the helicases by the p53 protein as a possi ble inactivation mechanism could be excluded. Instead, the anti-helica se activity can be explained by our finding that p53 binds with high a ffinity 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 alt er the secondary structure of RNA and/or to influence dynamic RNA - RN A interactions. These results, and the fact that the affinity of p53 t o RNA is about one order of magnitude higher than to single-stranded D NA, imply an RNA-specific function of p53 in vivo.