The Chinese hamster phosphoglycerate kinase gene family.

I. A phosphoglycerate kinase (PGK) deficient variant cell line, R1.1.7, derived from the Chinese hamster ovary cell line, CHO-K1, is used as a recipient in the development of a DNA-mediated transfection system designed for the study of in vivo expression of exogenous PGK gene sequences. II. Several PGK DNA sequences are detected in the Chinese hamster genome by hybridisation of genomic DNA digests with a human PGK cDNA probe. A number of these sequences are shown to be X-linked. Four of the PGK sequences observed in the blot hybridisations are isolated from a CHO-K1 DNA genomic library and analysed by probing with different regions of the PGK cDNA, heteroduplex mapping and DNA sequencing. One of these sequences is a 572 bp exon from the functional X-linked PGK gene (PGK-1) which is expressed in all somatic cells. The three remaining PGK sequences are intronless pseudogenes which were apparently derived independently, from an ancestral Chinese hamster PGK gene, within the last 50 million years. They exhibit features typical of 'processed' pseudogenes which are generated via an mRNA intermediate and integrated into breaks in the chromosomal DNA.