Changes in the methylation of transfer RNA in vaccinia infected HeLa cells

Abstract

Uridine-labeled HeLa tRNA, when chromatographed on benzoylated diethylaminoethyl cellulose (BD-cellulose), eluted in two peaks, A and B, which contained 53% and 47% of the total labeled tRNA, respectively. The ratio of peak A to peak B was about 1.15. Experiments with methyl-labeled tRNA suggested that the source of this chromatographic separation depended on the methyl groups found in the bases of the tRNA species. The tRNA species that eluted as peak A were relatively methyl-rich and contained 70% of the total methyl-labeled tRNA while those molecules that eluted later at the higher salt concentration as peak B were relatively methyl-poor and contained 30% of the total methyl-labeled tRNA. Infection of HeLa cells with vaccinia for 8 hr resulted in a significant change in the elution pattern of uridine-labeled tRNA. About 70% of the uridine-labeled tRNA was found to elute in the methyl-rich peak A while 30% was found to elute in the methyl-poor peak B. The ratio of uridine counts in peak A to peak B was about 2.20 compared to the 1.15 found in uninfected cells. Since preexisting tRNA was shown to be unaffected by vaccinia infection, it was concluded that in vaccinia-infected cells there was a substantial relative increase in the synthesis of methylated tRNA compared to normal cells.