Biochemical properties of Xenopus laevis p53

The p53 gene has evolutionarily highly conserved boxes from rainbow trout to man whereas other regions are divergent in different species. In order to define conserved and species specific properties of p53 we analyzed frog p53. Since the commonly available monoclonal antibodies do not react with Xenopus p53 we expressed a recently cloned Xenopus laevis cDNA in bacteria and this protein was used to generate polyclonal antibodies. This antibody recognizes p53 from Xenopus laevis oocytes, baculovirus infected insect cells and p53 from an in vitro transcription/translation reaction but not from somatic Xenopus tissue cells. In contrast to p53 from other species Xenopus p53 is mainly found in the cytoplasm. Xenopus p53 forms mainly tetramers as p53 from other species. Like p53 from other species Xenopus p53 is tightly associated with a protein kinase activity and phosphorylated by this associated enzyme. Xenopus p53 binds strongly to its own RNA without any influence on the translation of p53 mRNA. Thus, Xenopus p53 seems to have some properties in common with p53 from other species and some additional species specific features.