| Popis: |
Xenopus p53 cDNA, homologous to the human tumour suppressor p53, has previously been cloned from oocyte and gastrula libraries. In this report, we describe a polyclonal antibody 2674 raised against Xenopus p53 (Xp53) expressed in bacteria, that recognises proteins of approximately 52, 46 and 35 kDa present in Xenopus oocytes, parthenogenically activated eggs and in somatic tissue culture cells. We report here purification of Xp53 from insect cells infected with Xp53-baculovirus, and this protein is shown to be phosphorylated by casein kinase II but has low sequence-specific DNA binding activity. Using similar purification conditions, we have isolated endogenous Xp53, showing that Xenopus eggs 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 phosphorylation. u.v.-induced DNA damage of somatic Xenopus cells results in accumulation of Xp53. We suggest that the high levels of putative Xp53 detected in eggs may represent maternal stockpiles of a protein necessary to protect rapidly dividing cells from the effects of DNA damage. |
