A HUMAN DNA SEGMENT ENCOMPASSING LEUCINE AND METHIONINE TRANSFER-RNA PSEUDOGENES LOCALIZED OS CHROMOSOME-6

A human genomic clone, designated LHtlm8, that strongly hybridized to a mammalian leucine tRNA(IAG) probe, was found to encompass a pair of tRNA pseudogenes that are transcribed in a homologous cell extract. A leucine tRNA(AAG) pseudogene (TRLP1) is 2.1-kb upstream and of opposit e polarity to a methionine elongator tRNA(CAU), pseudogene (TRMEP1). T RLP1 has three nucleotide variations (97% identity) from its cognate l eucine tRNA(IAG), while TRMEP1 has a 78% identity with its cognate tRN A. Similar to a number of other eukaryotic tRNA pseudogenes, presumpti ve precursor tRNA transcripts are generated from the two pseudogenes i n vitro, but possibly due to their aberrant and unstable secondary and tertiary structures, no detectable mature tRNA products are observed. The two tRNA pseudogenes are encompassed within a 9.6-kb EcoRI fragme nt that has been assigned to the chromosomal locus, 6pter-q13, by Sout hern blot hybridization of human-rodent somatic cell hybrid DNAs with probes derived from the cloned tRNA pseudogenes and flanking sequences . A 4.4-kb EcoRI fragment also harbored in clone LHtlm8 was mapped to human chromosome 11, suggesting that the two EcoRI fragments were inad vertantly ligated together during construction of the genomic library.