Isolation of a mouse genomic clone containing four tRNACys-encoding genes.

A cluster of four tRNACys-encoding genes with the anticodon GCA was found on a murine genomic clone containing an 18-kb DNA insert. Three of the four genes encode the identical tRNA, whereas the fourth gene has an altered nucleotide (nt) sequence. Two of the genes within a 2-kb PvuII fragment have the same polarity and are separated by only 921 bp. These two tRNAs have a different primary sequence. The changes in the nt sequences occur within three stems of the tRNA cloverleaf structure and weaken the strength of the H-bonds within the stems. All four genes (designated i-iv) have the 3' structural element that has been proposed as the transcription termination signal [Bogenhagen and Brown, Cell 24 (1981) 261-270]. The remainder of the flanking regions of the three identical tRNAs are very similar to each other, whereas the flanking regions of the fourth tRNA are distinctly different.