Molecular Nature of Spontaneous Mutations in Mouse Lactate Dehydrogenase-A Processed Pseudogenes

Kayoko M. Fukasawa ¹, Masako Tanimura ², Ikuya Sakai ¹, Farida S. Sharief ¹, Fu-Zon Chung ¹, and Steven S.-L. Li ¹

¹ Laboratory of Genetics, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, North Carolina 27709
² Center for Demographic and Population Genetics, University of Texas, Houston, Texas 77030

The presence of at least ten mouse LDH-A pseudogenes was demonstrated in the genomic blot analysis, and four different processed pseudogenes have thus far been isolated and characterized. In this report, the nucleotide sequences of two different mouse lactate dehydrogenase-A processed pseudogenes, M11 and M14, were determined and compared with the protein-coding sequences of the mouse and rat LDH-A functional genes. In the pseudogene M11, the sequence of 64 nucleotides from codon no. 257 to 278 was tandemly duplicated. In the pseudogene M14, the sequence of 22 nucleotides from codon no. 68 to 75 was replaced by an inserted repetitive sequence of 242 nucleotides homologous to a mouse truncated R element. The pattern of nucleotide substitutions accumulated in mouse LDH-A pseudogenes M11 and M14, as well as that of pseudogene M10 identified previously, was analyzed, and the substitution frequencies of the C or G at the CG dinucleotide were found to be high.