Small molecular weight RNA components in Ehrlich ascites tumor cells

Abstract

Ehrlich ascites tumor cells contain five small molecular weight nuclear RNA components (small nRNA) (L, A, C, D, and F) which migrate slower than 5-S RNA by electrophoresis in 10 % polyacrylamide gels and three components (H components) which migrate between 5-S RNA and tRNA. The small nRNA components are specifically localized in the nucleus and they account for 0.2 to 0.7 % of the total cellular RNA and 0.7 to 2.9 % of the nuclear RNA. Apart from one H component, which shows high rate of labeling with [ 3H]uridine, the other small nRNA components are labeled with rates which are similar or somewhat less than tRNA and 5-S RNA, but 2–3 times higher than rRNA. When Ehrlich cells which have been labeled in vivo with [ 3H]uridine were incubated in vitro the radioactivity remained in the small nRNA components in the nucleus whereas the labeling in 5-S RNA and rRNA disappeared from the nucleus. Inhibition experiments divide the small nRNA components into two groups: One group consisting of the H components which are inhibited like tRNA and one group consisting of A, C, and D which are inhibited differently. The H-components are inhibited less by actinomycin and more by 3′-deoxyadenosine than component A, C and D. [ 3H]Methyl groups from [ Me- 3H]methionine are incorporated more into component C than into A and D. The incorporation of [ 3H]methyl groups in small nRNA components is higher than in rRNA, but much less than in tRNA. The corresponding small nRNA components from Ehrlich, Yoshida and L 5178 Y ascites cells have identical mobilities on 10 % polyacrylamide gels. Differences in mobilities of small nRNA components from HeLa cells and Ehrlich cells were found for component A and the H components. Furthermore component L was present in relatively larger amounts in Ehrlich cells than in HeLa cells whereas HeLa cell components B and K are absent in Ehrlich cells.