Ribonucleic acid synthesis in streptomyces antibioticus: Stable ribonucleic acid species synthesized by young and old cells

Abstract

In studies of RNA synthesis by intact cells and cell-free extracts of , it has been found that 48 hr cells (producing actinomycin) and cell-free extracts are less efficient than 12 hr cells (not producing actinomycin) and extracts in the synthesis of RNA. Analysis of the products of "in vivo" and "in vitro" RNA synthesis by sucrose gradient centrifugation reveals that both 12 and 48 hr cultures and cell-free extracts synthesize ribosomal RNA as well as RNA species of higher and lower molecular weights. However, 50-60% of the 3H-uridine labelled RNA synthesized by intact cells sediments as rRNA as compared with only 5-10% of the cell-free product. The addition of 2 x 10-5 M actinomycin D to incubation mixtures for cell-free RNA synthesis does not significantly alter the relative amounts of the various RNA species synthesized by 12 or 48 hr extracts.