CHARACTERIZATION AND TRANSCRIPTIONAL REGULATION OF RAT GLUTAMINE TRANSFER-RNA-ENCODING GENES - REPRESSION OF TRN(UUG)(GLN) SYNTHESIS

In rat liver, the amount of tRNA(UUG)(Gln) (RG-2) was found to be appr ox. 20% of that of tRNA(CUG)(Gln) (RG-1). The independent RG-1 and RG- 2 genes were isolated from a rat genomic library together with four RG -related genes containing two to five alterations in their coding regi ons. Sequence analysis demonstrated that there was no difference betwe en the internal promoter sequences of RG-1 and RG-2. However, interest ingly, the transcriptional activity of RG-1 was approximately four-tim es higher than that of RG-2 in an in vitro transcription reaction. Rep lacement of the 5'-flanking sequence of RG-2 by the corresponding sequ ence of RG-1 or by a plasmid DNA sequence caused activation of RG-2 tr anscription. Gel retardation assay demonstrated that the 5'-flanking r egion of RG-2 contained a unique sequence specifically recognized by a nuclear protein. Taken together, these results strongly suggest that the transcriptional activity of RG-2 might be negatively regulated by the binding of a nuclear protein at a specific site in the 5'-flanking region of the gene.