Repression of rRNA synthesis during slug reconstruction in Dictyostelium discoideum.

When cells dissociated from "slugs" are allowed to reaggregate, they reconstruct slugs. During this process, the cells showed a marked decrease in the ratio of labeled RNA lacking poly(A) to labeled total RNA as compared with that of cells in normal slugs. Irrespective of the change in total labeled RNA, the ratio remained low even after 6 h of reconstruction. Sucrose density gradient analysis of RNA showed that the synthesis of high molecular weight rRNA (26S and 17S) was considerably repressed in reconstructed slugs as compared with normal slugs. Polyacrylamide gel electrophoresis of low molecular weight rRNA revealed that the synthesis of 5S rRNA, but not 4S tRNA, was repressed.