Nucleotide sequence and transcription of a gene encoding human tRNA CCCGly

Abstract

A phage λ clone containing a 13.1-kb human DNA fragment was isolated and found to contain a tRNA gene encoding a glycine tRNA. The nucleotide sequence of the gene and its flanking regions has been determined. The gene does not have an intervening sequence nor does it encode the 3' -terminal CCA sequence found in mature tRNAs. Although this tRNA gene has an anticodon sequence of CCC, it has a striking homology (96%) with a human glycine tRNA which has an anticodon of GCC. As in other eukaryotic tRNA genes, the coding region contains a characteristic internal split promoter sequence, and the 3'-flanking region has a typical RNA polymerase III termination site of five consecutive T residues. There is no apparent sequence in the 5' -flanking region which could serve as a regulatory element. This gene is accurately transcribed in vitro by RNA polymerase III using a HeLa cell-free system. During the course of in vitro transcription, larger precursor tRNA CCC Gly transcripts are processed to yield a mature-sized tRNA product. A precursor-product relationship was established by comparing the ribonuclease A fingerprints of the precursor and product tRNA transcripts.