Expression of the p53 homologue p630 alpha and Delta Np63 alpha in normal and neoplastic cells

A burgeoning family of p53-related genes have been described recently, incl uding p73 and p63, Both these genes encode proteins with many similarities to p53 but also with the potential for forming a range of related species b y alternative promoter usage and alternative splicing. In order to begin th e characterization of p63, we generated a polyclonal serum (designated SC1) that recognizes the C-terminus of p63 alpha. We have shown that this reage nt recognizes p63 alpha but not p53 nor p73, By western blot analysis both p63 alpha and the N-terminal truncated form of p63 alpha (Delta Np63 alpha) were found in a range of cell lines. Similar immunoblot analysis of tissue s reveals considerable complexity with at least four SC1-immunoreactive iso forms being identified. In immunohistological studies SC1 immunoreactivity is widely detectable, being predominantly associated with proliferative com partments in epithelia. However, non-proliferative populations can also sho w SC1 immunostaining, No simple relationship between the isoforms identifie d by immunoblotting of tissue lysates and the tissue immunostaining charact eristics was identified. A previously unrecognized species intermediate in mobility between p63 alpha and Delta Np63 alpha was found in several tissue s, including nerve and peripheral blood lymphocytes, Interestingly, there i s suppression of p63 alpha expression in HaCat cells in a time- and concent ration-dependent manner after UV and MMS treatment. Our data provide furthe r information about the complexity of p63 and the SC1 serum will prove to b e a useful tool in further studies of this p53 homologue.