Role of c-myc in simian virus 40 large tumor antigen-induced DNA synthesis in quiescent 3T3-L1 mouse fibroblasts.
Stably transfected NIH 3T3-L1 mouse fibroblasts (L1 cells) expressing the simian virus 40 large tumor antigen (LTAg) maintain c-myc expression and proliferation in low serum, whereas cells expressing the mutant form LTAg-K1, defective in binding of the retinoblastoma suppressor gene product pRb, showed reduced levels of c-myc RNA and only background levels of DNA synthesis in low serum. The role of the c-Myc protein in LTAg-induced DNA synthesis was studied in microinjection experiments. Expression of LTAg induced cellular DNA synthesis in > 95% of microinjected serum-starved L1 cells, whereas the mutant LTAg-K1 could not induce DNA synthesis. Coexpression of dominant negative c-Myc or Max mutants with LTAg inhibited DNA synthesis, indicating that functional c-Myc is necessary for induction of DNA synthesis by LTAg. Expression of c-Myc induced programmed cell death (apoptosis) in serum-starved L1 cells. Coexpression of c-Myc with LTAg-K1 restored induction of DNA synthesis without apoptosis. Expression of a truncated LTAg, LTAg-(1-259), defective in binding of the tumor suppressor gene product p53, failed to prevent c-Myc-induced apoptosis. The data indicate that c-Myc can restore the ability of LTAg-K1 to induce DNA synthesis and that LTAg-K1 prevents c-Myc- induced apoptosis in serum-starved L1 cells by its interaction with p53.[1]References
- Role of c-myc in simian virus 40 large tumor antigen-induced DNA synthesis in quiescent 3T3-L1 mouse fibroblasts. Hermeking, H., Wolf, D.A., Kohlhuber, F., Dickmanns, A., Billaud, M., Fanning, E., Eick, D. Proc. Natl. Acad. Sci. U.S.A. (1994) [Pubmed]
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