Establishment Of Conditional Expression Of C-myc In Transgenic Mice And Tumor Model By The Tet-On System

Tet-Off/Tet-On system is that the Tet repressor protein (TetR) negatively regulates the genes of the tetracycline-resistance operon on the TnlO transposon. Conditional oncogene expression in transgenic mice is of interest for studying the oncoprotein requirements during tumorigenesis that can be induced to undergo growth arrest and enhance their differentiated functions. Both tetracycline-controlled transactivator(tTA) and reverse tTA(rtTA) of which tTA activates transcription in the absence of doxycycline(Dox) and rtTA in the presence of Dox , respectively, have allowed controlling gene expression of transgenic mice precisely in a spatiotemporal fashion, providing unique genetic models for the study of development process and high-order functions. The c-myc proto-oncogene encodes the transcription factor, and was originally identified as the cellular homologue to the viral oncogene (v-myc) of the avian myelocytomatosis retrovirus. That c-myc might promote cell proliferation have resulted from a number of important studies revealing c-myc ability to activate or repress target genes involved in cell cycle progression which is regarded as an essential event in c-myc-induced Gl-S progression, which leads to uncontrolled cellular proliferation and tumor formation. Oncoprotein such as c-myc?potent iriducer of cell proliferation --as shown to possess apoptosis activity. C-myc initially induced pancreatic b cell apoptosis.First of all, c-myc gene of human was amplified by reverse transcript polymerase chain reaction ( RT-PCR ) technique from Hela cell line and cloned into pTZ57R/T vector for sequence analysis, Recombinant plasmid pTZ57R/T-c-/wyc was constructed. The sequence analysis showed that the gene was consistent with that of GeneBank in predicted amino acid. The c-myc gene was subcloned into the expressing vector pTRE2 of Tet-On system. Then pTRE2-c-myc-Hyg was obtained, and was expressed in vitro after rtTA expressed by the transfection. Then double-stable cell lines were selected.