Restoration of Mitochondrial Gene Expression Using a Cloned Human Gene in Chinese Hamster Lung Cell Mutant
Background: Gal-32 is a Chinese hamster lung cell nuclear mutant that is unable to grow in galactose due to a defect in mitochondrial protein synthesis. Since the product of the Gal-32 gene was unknown, it was imperative to use phenotypic complementation to clone a human gene that corrected the Gal-32 mutation.
Results: Recessive Gal-32 cells were co-transformed with pSV2-neo plasmid DNA and recombinant DNA from a human genomic library containing the dominant human Gal+ gene and a chloramphenicol-resistance (camr) gene present in the pSV13 vector. Primary transformants were selected by growth in galactose and the neomycin analog G418. In order to rescue the human Gal+ gene, a genomic library was constructed with primary transformant DNA and the pCV108 cosmid vector. The camr gene was used to identify clones with the nearby human sequences. DNA from two camr, Alu-hybridizing clones was able to transform the recessive Gal-32 cells to the Gal+ phenotype and to restore mitochondrial protein synthesis.
Conclusion: These data demonstrate the isolation of two pCV108-transformant recombinant clones containing a human gene that complements the Chinese hamster Gal-32 mutation and restores galactose metabolism.