Immortalized mouse cell lines that lack a functional Rev3 gene are hypersensitive to UV irradiation and cisplatin treatment

The catalytic subunit of polymerase zeta is encoded from the Rev3 gene. The enzyme is conserved through eukaryotic evolution and its main function appears to be translesion synthesis (TLS) over damaged bases that stall DNA replication. In non-vertebrate cells, inactivation of polymerase zeta results in a moderate hypersensitivity to DNA damage but no proliferative defect in the absence of exogenous damage. Mouse embryos that lack Rev3 however have a severe growth defect and are aborted at midgestation. This has suggested that polymerase zeta may be involved in vital processes in mammalian cells. Here we describe the establishment of immortalized mouse fibroblast cell lines that lack a functional Rev3 gene. These were established from homozygously Rev3-targeted mouse embryos that were also heterozygously targeted at the p53 locus, but the cell lines lost the wild type p53 allele during transformation. Cell lines in which the Rev3 gene is targeted on both alleles grow more slowly than control lines and the deficiency is also associated with an increased frequency of cells at the G2/M phase of the cell cycle and augmented apoptosis. Targeted cells are hypersensitive to UV irradiation and cisplatin treatment and arrest at the S or G2/M phase of the cell cycle if exposed to these treatments. Thus, although vital for murine embryonic development, polymerase zeta activity is not essential for continuous proliferation of transformed mammalian cells that lack p53. It does, however, appear to play an important role in allowing mammalian cells to tolerate DNA damage.