A NOVEL PROTEIN WITH STRONG HOMOLOGY TO THE TUMOR-SUPPRESSOR P53

The p53 tumor important genes apoptosis. Mice deficient for p53 show a high incidence of cancer but are developmentally normal suggesting th at compensatory mechanisms exist in embryogenesis and differentiation. The new KET protein is the first mammalian protein with strong homolo gy to p53 in all evolutionary conserved regions. This conservation mak es a functional redundancy of the two proteins in cell-cycle control p ossible. KET is expressed during embryonic development and in certain adult tissues. Among all of the known p53 proteins of different specie s KET is most closely related to that found in squid. The relationship between KET and the invertebrate p53 protein sheds light on the evolu tionary origin of p53. KET appears to be an ancestral p53-related prot ein in vertebrates,vith a possible role in development and differentia tion while the ubiquitously expressed p53 protein attained its general role as 'guardian of the genome' during evolution.