Alterations in p53 and E2F-1 function common to immortalized chicken embryo fibroblasts

A number of non-virally and non-chemically immortalized chicken embryo fibr oblast (CEF) cells have been established recently in continuous cell cultur e. All immortal CEF cells tested showed common genetic alterations in the e xpression patterns of p53 and E2F-1 mRNA and protein which were down- and u p-regulated, respectively, The biological effects of differentially regulat ed p53 and E2F-1 were determined by reporter gene transcriptional activity assays, DNA binding assays, and Northern blot analysis of the expression pa tterns of down-stream genes, In addition, expression of most of the cyclin genes was up-regulated in immortal CEF cells, which may be associated with the rapid cell division rates and serum-independent growth patterns seen in immortal CEF cells. The telomeric lengths and chromosome integrity were ma intained in all immortal CEF cell lines without detectable telomerase activ ity. Although the functional inactivations of the p53 and Rb regulatory pat hways are known to be common events for cellular immortalization, the genet ic changes leading to alteration of p53 and E2F-1 function through transcri ptional and post-transcriptional regulation seem to be unique in immortal C EF cells.