The effects of cycloheximide upon transcription of rRNA, 5 S RNA, and tRNA genes.
The effects of inhibitors of protein synthesis upon transcription have been re-examined. Cycloheximide (1 microgram/ml) inhibits incorporation of uridine into RNA of P1798.S20 lymphosarcoma cells. Filter hybridization studies indicate that labeling of pre-rRNA is inhibited 60-80% after 1 h and quantitative S1 nuclease mapping reveals a corresponding decrease in the amount of cellular pre-rRNA. Cycloheximide also inhibits labeling of 5 S RNA and tRNA, but incorporation of uridine into poly(A+) RNA is unaffected. Transcription experiments carried out in nuclei from cycloheximide-treated cells indicate that the inhibitor causes a selective decrease in the activity of RNA polymerases I and III. Cell-free extracts from P1798.S20 were used to transcribe the cloned mouse rRNA gene, Syrian hamster 5 S RNA gene, and the Drosophila tRNAArg gene. Extracts from cycloheximide-treated cells were inhibited in this respect. Transcription of rRNA and 5 S RNA genes was inhibited by 90% after 2 h and 50% inhibition occurred within 20-30 min. Transcription of the tRNA gene was inhibited 75% after 2 h with a half-time of approximately 1 h. Inhibition was due neither to a direct effect of cycloheximide nor to the presence of nucleases or diffusible inhibitors of transcription. Moreover, transcription of rDNA in extracts from cycloheximide-treated cells could be restored by the addition of a partially purified initiation factor preparation. The data indicate that inhibition of protein synthesis results in rapid depletion of transcription factors that are required for initiation by RNA polymerases I and III. Among these is the glucocorticoid-regulated rDNA initiation factor designated TFIC.
Gokal
P K
PK
Cavanaugh
A H
AH
Thompson
E A
EA
D000818:Animals; D006224:Cricetinae; D003513:Cycloheximide / Q000494:pharmacology*; D004275:DNA, Ribosomal / Q000378:metabolism; D004640:Emetine / Q000494:pharmacology; D008647:Mesocricetus; D051379:Mice; D010448:Peptide Initiation Factors / Q000378:metabolism; D012313:RNA / Q000235:genetics*; D012318:RNA Polymerase I / Q000037:antagonists & inhibitors; D012320:RNA Polymerase III / Q000037:antagonists & inhibitors; D012335:RNA, Ribosomal / Q000235:genetics*; D012343:RNA, Transfer / Q000235:genetics*; D013997:Time Factors; D014158:Transcription, Genetic / Q000187:drug effects*
D004275:DNA, Ribosomal; D010448:Peptide Initiation Factors; D012335:RNA, Ribosomal; D012313:RNA; D012343:RNA, Transfer; D003513:Cycloheximide; D012318:RNA Polymerase I; D012320:RNA Polymerase III; D004640:Emetine