The First Human Genes for tRNA Arg ICG,tRNA Gly UCC,and tRNA Thr IGU and More tRNA Val Pseudogenes: Expression and Pre-tRNA Maturation in HeLa Cell-Free Extracts

Abstract

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