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[Effects of pol beta on biological characteristics and DNA damage in mouse embryonic fibroblast].

OBJECTIVE
To explore the effect of DNA polymerase beta (pol beta) expression level on biological characteristics of mouse embryonic fibroblast (MEF) and the cellular response to DNA damage induced by potassium dichromate.


METHODS
pol beta wild-type cells (pol beta +/+), pol beta null cells (pol beta -/-) and pol beta overexpressed cells (pol beta oe) were applied as a model system. The growth curve of cells was plotted by MTT assay; the doubling time of cells was detected by double time experiment; the spontaneous mutation frequency was determined by HGPRT gene mutation method and single cell gel electrophoresis assay (SCGE) was employed to observe the DNA damage either happened spontaneously or induced by potassium dichromate.


RESULTS
Growth characteristic and doubling time of the three kinds of cells were similar and no obvious differences were found on spontaneous DNA damage and mutations frequency among them (P > 0.05). Potassium dichromate increased comet rate and tail length in the three kinds of cells in a concentration dependent way. DNA damage of pol beta -/- cells at the same dosage were more serious than the other cells both in comet rate and tail length (P < 0.05). pol beta oe cells demonstrated more resistant to DNA damage obviously than the others.


CONCLUSION
The expression level of pol beta has no significant effect on the biological characteristic and spontaneous mutation frequency of MEF. pol beta knock out cells is more sensitive to DNA damage induced by potassium dichromate, whereas, pol beta over expression can help cells response to DNA damage and protect cells from death in a certain degree.