XENOPUS P53 IS BIOCHEMICALLY SIMILAR TO THE HUMAN TUMOR-SUPPRESSOR PROTEIN P53 AND IS INDUCED UPON DNA-DAMAGE IN SOMATIC-CELLS

Xenopus p53 cDNA, homologous to the human tumour suppressor p53, has p reviously been cloned from oocyte and gastrula libraries. In this repo rt, we describe a polyclonal antibody 2674 raised against Xenopus p53 (Xp53) expressed in bacteria, that recognises proteins of approximatel y 52, 46 and 35 kDa present in Xenopus oocytes, parthenogenically acti vated eggs and in somatic tissue culture cells. We report here purific ation of Xp53 from insect cells infected with XpS3-baculovirus, and th is protein is shown to be phosphorylated by casein kinase II but has l ow sequence-specific DNA binding activity. Using similar purification conditions, we have isolated endogenous Xp53, shelving that Xenopus eg gs contain high levels of p53 protein. Xp53 from eggs binds to the p53 -specific DNA-binding consensus sequence. Two dimensional gel analysis indicates that Xp53 from eggs may exist in various states of phosphor ylation. u.v.-induced DNA damage of somatic Xenopus cells results in a ccumulation of Xp53. We suggest that the high levels of putative Xp53 detected in eggs may represent maternal stockpiles of a protein necess ary to protect rapidly dividing cells from the effects of DNA damage.