An intron-containing tRNAArg gene within a large cluster of human tRNA genes

The insert within lambda Ht363, a recombinant selected from a bank of human genomic DNA cloned in lambda Ch4A, is described. Southern blot hybridization with a mixed tRNA[32P]pCp probe revealed the presence of four tRNA genes, which were shown to represent further copies of genes previously identified as a solitary tRNAGly gene and as a three gene cluster on two different recombinants. In vitro transcription of a fragment containing the three gene cluster revealed the presence of a further pol III gene, which was shown to be that for a tRNAArgTCT. This gene contains a 15 bp intron, the presence of which presumably prevented its detection on Southern blots by tRNA hybridisation. The gene is present in the previously reported cluster and occurs in higher copy number (> 7) in other arrangements in the genome. Most of the copies of the gene have related intron sequences.