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

The rapid destabilization of p53 mRNA in immortal chicken embryo fibroblast cells

“…The expression of p53 mRNA and p53 protein was downregulated in all immortal CEF cells tested compared to primary CEF cells (Figure 1a; Kim et al, 2001b). Loss of p53 transcriptional activity was also determined by reporter gene assays, DNA binding assays, and Northern blot analysis of the expression patterns of down-stream genes (Kim et al, 2001b).…”

Cellular characteristics of primary and immortal canine embryonic fibroblast cells

“…The three immortal CaEF cell lines grown in the presence of adriamycin did not display evident DNA damage responses such as cell cycle arrest or cell death, while primary cell growth was significantly decreased by the same treatment. The finding that forced overexpression of wild-type p53 did not induce cell cycle arrest or cell death in immortal CGFR-Ca-1 and -3 cell lines could be explained by the CGFR-Ca-1 and -3 cell lines having unidentified mechanisms to rapidly degrade exogenous p53 as suggested by our previous study (Kim et al, 2001). However, like primary CaEF cells, immortal CGFRCa-2 cells exogenously transduced with wild-type p53 displayed a significant decrease in viable cell numbers, indicating that the CGFR-Ca-2 cell line plausibly inactivated the p53 gene itself.…”

“…One CGFR-Ca-2 cell line was found to have a mutant p53 protein, while CGFR-Ca-1 and -3 cell lines did not express detectable levels of p53 mRNA and protein as determined by semi-quantitative RT-PCR and western blot analysis, respectively. Although the molecular mechanism leading to the downregulation of the p53 mRNA in the CGFR-Ca-1 and -3 cell lines is currently unclear, it is possible that p53 mRNA in the CGFR-Ca-1 and -3 cell lines might be rapidly degraded as shown in spontaneously immortalized avian cell lines observed in our previous data (Kim et al, 2001). The three immortal CaEF cell lines grown in the presence of adriamycin did not display evident DNA damage responses such as cell cycle arrest or cell death, while primary cell growth was significantly decreased by the same treatment.…”

“…Spontaneous immortalization in human and chicken cells is extremely rare (Harris, 1987;Kim et al, 2001), whereas this event in mouse cells is known to occur by the order of magnitudes greater than the rate observed in human and chicken cells. Currently, there exist just a few reporting on the spontaneous immortalization of canine cells.…”

Truncated N-terminal mutants of SV40 large T antigen as minimal immortalizing agents for CNS cells

“…The LXCXE motif (residues 103-107) binds the retinoblastoma protein (pRb) and family members p107 and p130 (DeCaprio et al, 1988;Stubdal et al, 1996). It is believed that the N-terminal DnaJ domain cooperates with the Rb-binding domain to dissociate Rb-E2F complexes, thereby promoting re-entry of non-dividing cells into the cell cycle (Kim et al, 2001a;Zalvide et al, 1998). In the carboxyl half of LT, two regions within residues 351-626 function as p53-binding and inactivating domains (Kim et al, 2001b;Lane and Crawford, 1979;Linzer and Levine, 1979;Sarnow et al, 1982).…”