Conditional cell transformation by doxycycline-controlled expression of the MC29 v-myc allele.
Virology
; 253(2): 193-207, 1999 Jan 20.
Article
in En
| MEDLINE
| ID: mdl-9918878
ABSTRACT
To investigate the molecular basis of oncogenesis induced by the v-myc oncogene of avian myelocytomatosis virus MC29, we developed a conditional cell transformation system in which expression of the MC29 v-myc allele is dependent on a doxycycline-sensitive transactivator (tTA). Clonal lines of quail embryo fibroblasts transformed by doxycycline-controlled v-myc revert to the normal phenotype and lose their ability to grow in soft agar after the addition of doxycycline. Repression of v-myc causes the cells to withdraw from the cell cycle, and long-term survival in culture requires reexpression of v-myc. Although complete repression of v-myc mRNA and v-Myc protein in these cells occurs within 14 h after the addition of doxycycline, the first morphological alterations are observed after 24 h, and after 3 days, the morphology changed entirely from small rounded cells showing a typical myc-transformed phenotype to large flat cells resembling normal fibroblasts. Cells exposed to doxycycline for 3 days reexpressed v-myc within 24 h after withdrawal of the drug from the culture medium, partial retransformation occurred after 2 days, and complete morphological transformation was reestablished after 6 days. Analogous results were obtained with a cell line in which expression of the v-myc allele is dependent on a reverse transactivator (rtTA) that is activated by doxycycline. The striking differential expression of known transformation-sensitive genes and of new candidate v-myc target genes revealed the tightness of the doxycycline-controlled v-myc expression system. The data also indicate that expression of v-myc in these cells is indispensable for enhanced proliferation, transformation, and immortalization.
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Collection:
01-internacional
Database:
MEDLINE
Main subject:
Gene Expression Regulation, Viral
/
Cell Transformation, Viral
/
Oncogene Protein p55(v-myc)
/
Doxycycline
/
Alleles
Limits:
Animals
Language:
En
Journal:
Virology
Year:
1999
Document type:
Article
Affiliation country:
Austria