INCORPORATION OF 5-FLUOROURACIL INTO TRANSFER RNA OF ESCHERICHIA COLI K12W6 AND ITS EFFECT ON METHYLATION OF URACIL

5-Fluorouracil was incorporated into the tRNA of Escherichia coli K12W6 met- RCrel under conditions of growth and starvation. The tRNA was isolated and, in the latter case, further methylated in vitro. It was shown that the tRNA isolated from growing cells as well as the tRNA methylated in vitro contained reduced levels of 5-methyluridylic acid. An analysis of the relationship between the amount of 5-fluorouracil incorporated into the tRNA and the percentage decrease in the methylation of uracil to 5-methyluracil under conditions in vivo and in vitro indicated that the incorporation of 5-fluorouracil into the uracil position which is subsequently modified to yield 5-methyluracil is nonrandom. © 1969.