High frequency variation in mammary tumor virus expression in cell culture
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Summary
This summary is machine-generated.Murine mammary tumor virus (MMTV) expression in cell lines shows a high rate of conversion to a lower expression level. This MMTV(L) variant formation is much faster than typical mutation rates.
Area Of Science
- * Virology and Molecular Biology
- * Cancer Research
- * Genetics and Epigenetics
Background
- * Murine mammary tumor virus (MMTV) is a retrovirus associated with mammary tumors in mice.
- * Understanding MMTV expression regulation is crucial for cancer research.
Purpose Of The Study
- * To investigate the rate and nature of MMTV expression changes in cultured murine mammary cells.
- * To compare MMTV expression variant formation with known mutation rates.
Main Methods
- * Culturing clonal derivatives of C3HMT murine mammary cell lines.
- * Quantifying MMTV expression levels (MMTV(H) and MMTV(L)).
- * Generating somatic cell hybrids to study MMTV expression regulation.
Main Results
- * MMTV expression conversion occurs at a high rate (approx. 6/100 clones), primarily from MMTV(H) to MMTV(L).
- * This high rate contrasts sharply with the low rate of 6-thioguanine resistance development (approx. 3/million cells).
- * Somatic cell hybrids indicate that constitutive MMTV expression and dexamethasone inducibility are dominant traits.
Conclusions
- * MMTV expression is regulated by at least two positive control mechanisms: constitutive expression and glucocorticoid stimulation.
- * Constitutive MMTV expression is unstable and subject to frequent variant formation.
- * The high rate of MMTV(L) variant conversion suggests a non-mutational or highly efficient mutational mechanism.