The First Human Genes for tRNAArgICG, tRNAGlyUCC, and tRNAThrIGUand More tRNAValPseudogenes: Expression and Pre-tRNA Maturation in HeLa Cell-Free Extracts

A functional tRNAVal gene, which codes for the major tRNAValIAC isoacceptor species, and three new tRNAVal pseudogenes have been isolated from human genomic DNA. Two tRNAVal pseudogenes and a tRNAVal variant gene were found to be associated with tRNA genes encoding tRNAArgICG, tRNAGlyUCC, and tRNAThrIGU, respectively, on distinct DNA fragments. All tRNA genes, including the pseudogenes, are actively transcribed in HeLa nuclear extract. Pre-tRNAs of tRNAVal, tRNAArg, tRNAThr, and tRNAGly genes are correctly processed to mature-sized tRNAs, whereas the three tRNAVal pseudogenes yield stable pre-tRNAs in vitro. These findings reveal that, together with the three known pseudogenes, half of the members of the human tRNAVal gene family are pseudogenes, all of which are active in homologous nuclear extracts in vitro and presumably also in vivo.