Immortalization of human embryonic fibroblasts by overexpression of c-myc and simian virus 40 large T antigen.
SV40 large T antigen, a viral oncoprotein, is known to immortalize human diploid fibroblast by soaking up cellular RB and p53, but its frequency is extremely low. Additional genetic alteration is necessary for single-step immortalization. We attempted to find out what this alteration is by overexpressing cellular signal mediator genes; c-myc and cyclin D frequently amplified in many cancer cells. Overexpression of cyclin D did not affect the immortalization, but, overexpression of c-myc along with T antigen could immortalize normal human diploid fibroblast. Several cellular markers tested during immortalization process showed that p21, a cyclin-dependent kinase inhibitor and a marker of cellular senescence, disappeared in the life span-extended cells by T antigen and in the immortalized cells by c-myc. p21 was, however, elevated in the senescent cells and in the cells of crisis. Interestingly, p16 was upregulated whenever T antigen is overexpressed. Telomerase activity was also activated only in the immortalized cells. These results suggest that overexpression of c-myc contributes to immortalization of human diploid fibroblast by activating telomerase activity and suppressing p21 activity.
Kim
H S
HS
Department of Biochemistry, College of Medicine, Hallym University, Chunchon, Kangwon-do, Korea.
Shin
J Y
JY
Yun
J Y
JY
Ahn
D K
DK
Le
J Y
JY
D000952:Antigens, Polyomavirus Transforming / Q000235:genetics / Q000378:metabolism*; D015415:Biomarkers; D002472:Cell Transformation, Viral; D002478:Cells, Cultured; D016922:Cellular Senescence / Q000235:genetics*; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000378:metabolism; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000378:metabolism; D004171:Diploidy; D005347:Fibroblasts / Q000378:metabolism*; D016259:Genes, myc / Q000235:genetics*; D006801:Humans; D013539:Simian virus 40 / Q000235:genetics; D019098:Telomerase / Q000378:metabolism
D000952:Antigens, Polyomavirus Transforming; D015415:Biomarkers; C493956:CDKN1A protein, human; D019941:Cyclin-Dependent Kinase Inhibitor p16; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D019098:Telomerase