Deregulated c—myc expression in quiescent CHO cells induces target gene transcription and subsequent apoptotic phenotype

Human c-myc cDNA was fused with the hormonebinding domain (HBD) cDNA of murine estrogen receptor gene and the chimeric gene was introduced into the CHO cells.The fusion protein,c-MycER,becomes activated when the synthetic steroid,4-hydroxy-tamoxifen (OHT),binds HBD.Activated c-MycER,likely c-Myc,can induce quiescent CHO cells reentry into S phase and subsequent cell death under serum-free condition.In addition,the expression of some proposed c-myc target genes such as ODC,MrDb,cad,rccl and rcl were found to increase upon OHT induction before S phase entry and apoptosis,indicating that these target genes are involved in cell cycle regulation and/or apoptosis control.However,the mutant D106-143c-MycER protein does not have above activities.

Deregulated c-myc expression in quiescent CHO cells induces target gene transcription and subsequent apoptotic phenotype

Human c-myc cDNA was fused with the hormonebinding domain (HBD) cDNA of murine estrogen receptorgene and the chimeric gene was introduced into the CHOcells. The fusion protein, c-MycER, becomes activatedwhen the synthetic steroid, 4-hydroxy-tamoxifen (OHT),binds HBD. Activated c-MycER, likely c-Myc, can inducequiescent CHO cells reentry into S phase and subsequentcell death under serum-free condition. In addition, theexpression of some proposed c-myc target genes such asODC, MrDb, cad, rcc1 and rc1 were found to increase uponOHT induction before S, phase entry and apoptosis, indicating that these target genes are involved in cell cycleregulation and/or apoptosis control. However, the mutantD106-143c-MycER protein does not have above activities.