A human DNA segment encompassing leucine and methionine tRNA pseudogenes localized on chromosome 6

The human family of Deafness/Dystonia peptide (DDP) related mitochondrial import proteins

The gene responsible for the human genetic neurodegenerative disorder DFN-1/MTS encodes a small protein known as deafness/dystonia peptide (DDP). It bears a strong resemblance to a recently characterized set of zinc-binding yeast proteins (Tim8p, Tim9p, Tim10p, Tim12p, and Tim13p) that are implicated in the import of a class of transmembrane carrier proteins from the cytoplasm to the mitochondrial inner membrane. We describe here the human complement of DDP/Tim-like proteins and establish the likely orthologous relationships between sequences from human, yeast, and other organisms. We also describe the expression patterns and chromosomal locations of their genes, which are candidate loci for autosomal recessive neurodegenerative disorders.

Analysis of selenocysteine (Sec) tRNA([Ser]Sec) genes in Chinese hamsters

Several recent observations have indicated that the primary structure of the Chinese hamster selenocysteine tRNA([Ser]sec) is different than those of other mammalian species. These reports prompted us to investigate the gene sequence for this tRNA in Chinese hamsters. Southern blotting of Chinese hamster ovary (CHO) genomic DNA derived from cultured cells with a tRNA([Ser]sec) probe indicated several hybridizing bands, and each of the corresponding genetic loci was isolated from a recombinant CHO library by molecular cloning. Sequence analysis of these regions indicated three likely pseudogenes and a single functional gene whose sequence differed from those of other mammals. Of these, only one pseudogene and the putative functional gene are actively transcribed following their microinjection into Xenopus oocytes. The possibility that the functional CHO tRNA([Ser]sec) evolved from an edited transcript is discussed.