Characterization of a tyrosine tRNA from a suppressor mutant of drosophila melanogaster

Transfer RNA, in particular, tyrosine tRNA, has been implicated in the mechanism of suppression mediated by the sus locus. Drosophila melanogaster tRNA^tyr can be separated into two major isoacceptors by RPC-5 chromatography. The early eluting isoacceptor, tRNA^tyr_Q, has the anticodon QψA, while the late eluting isoacceptor, tRNA^tyr_G, has the anticodon GψA. Previous evidence has indicated that both isoacceptors of Drosophila melanogaster tRNA^tyr_G from v; bw and a suppressor strain, su(s)²v; bw, differ in their biological activities. The chemical basis for this difference is explored. A procedure for purifying tRNA^tyr from Drosophila melanogaster without exposing the tRNA to enzymes or chemicals that might cause alterations is developed, and this procedure is used to purify Drosophila melanogaster tRNA^tyr_G from v; bw and su(s)²v; bw. The nucleoside compositions of the two tRNAs are then determined and compared. The su(spv; bw tRNA^tyr_G appears to contain one more N₂, N₂-dimethylguanosine and pseudoruidine than the v; bw tRNA^tyr_G. Further confirmation that the two tRNAs are different is obtained by comparing the fingerprint patterns of the two tRNAs that were generated by digestion with T₁RNase. One fragment in the su(s)²v; bw is identified that migrates faster than the corresponding fragment in the v; bw strain, indicating that the base composition of the two fragments and thus the two tRNAs are different. It is suggested that the sus locus is responsible for the difference in base composition of the v; bw and su(s)²v; bw tyrosine tRNAs, and that tyrosine tRNA may be involved in the mechanism of suppression mediated by the sus locus.