A treatment of primary mouse kidney cell cultures with 5 microM Ethidium Bromide (Eth Br) reduces the transcription of nuclear-coded genes and especially of ribosomal RNA genes. This effect was consistently observed when comparing drug-treated and control cells for (i), the incorporation of 3H uridine into total nuclear and B RNA polymerases as determined in isolated nuclei. It became more pron...

The eukaryotic 25 S, 18 S, and 5.8 S rRNAs are synthesized as a single transcript with two internal transcribed spacers (ITS1 and ITS2), which are removed by endo- and exoribonucleolytic steps to produce mature rRNA. Genetic selection for suppressors of a polyadenylation defect yielded two cold-sensitive alleles of a gene that we named RRP6 (ribosomal RNA processing). Molecular cloning of RRP6 ...

The inhibition of ribosomal RNA (rRNA) maturation by 5-fluorouridine (FUrd) in Novikoff hepatoma cells appears to depend upon the incorporation of the analog into the 45 S rRNA precursor. Precursor synthesized in the presence of FUrd is not processed into mature rRNA, but precursor synthesized in the absence of the analog is processed normally after the addition of the drug. The effect of FUrd ...

The specificity of transcription of Euglena gracilis Z chloroplast DNA by chloroplast DNA-dependent RNA polymerase in a transcriptionally active chromosome (Hallick, R.B., Lipper, C., Richards, O.C., and Rutter, W.J. (1976) Biochemistry 15, 3039-3045) has been studied. RNA molecules are both initiated and elongated in vitro. The RNA transcripts have been characterized as to their size, nuclease...

Cadmium Modification of Nucleolar Function and Structure in Physurum polycephalum. SINA, J. F., AND CHIN, B. (1979). Toxicol. Appl. PharmacoI. SO, 253-259. Exposure of Physurum to CdSO,, 1.5 x lo-’ M for 2-3 hr in early S phase (the onset of DNA synthesis and nucleolar reconstruction) resulted in the appearance of ring-shaped nucleoli. We have investigated the effects of cadmium on nucleolar (r...