Chromosomal assignment of amplified genes in hydroxyurea-resistant hamster cells

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Abstract
We have shown previously that cDNAs for the Ml and M2 subunits of ribonucleotide reductase, ornithine decarboxylase (ODC), and p5–8, a 55,000-Dalton protein, hybridize to amplified genomic sequences in a highly hydroxyurea-resistant hamster cell line. We have extended these observations to include two additional, independently isolated, hydroxyurea-resistant cell lines: SC8, a single-step hamster ovary cell line, and KH450, a multistep human myeloid leukemic cell line, have also undergone genomic amplification for sequences homologous to ODC and p5–8 cDNAs. However, neither SC8 nor KH450 contains amplified genomic sequences homologous to an Ml cDNA probe. A panel of mouse-hamster somatic cell hybrids was used to map sequences homologous to Ml, M2, ODC, and 5–8 cDNAs in the hamster genome. The M2, ODC, and p5–8 cDNAs hybridized to DNA fragments that segregated with hamster chromosome 7. In contrast, Ml cDNA hybridized to DNA fragments that segregated with hamster chromosome 3. These data suggest that the genes RRM2, (M2), ODC, and p5–8, but not RRM1 (Ml), are linked and may have been co-amplified in the selection of the hydroxyurea-resistant hamster and human cell lines.

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