Gene amplification: the Chinese hamster glutamine synthetase gene

The glutamine analogue, methionine sulphoximine, has been used to develop Chinese hamster ovary cell lines which overproduce the enzyme glutamine synthetase. Southern and Northern blot hybridization studies showed that this overproduction is due to gene amplification of a region of DNA containing the glutamine synthesis gene coding sequences, with a corresponding increase in glutamine synthetase mRNA and protein. This amplification has increased the glutamine synthetase gene copy number to approximately 1000 copies per cell. Genomic DNA sequences from the amplified region have been cloned and the structure of the glutamine synthetase gene within this region is being analysed.