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Altered subcellular distribution of U3 snRNA in response to serum in mouse fibroblasts.

Abstract
To extend our understanding of the mechanisms regulating ribosome biosynthesis during changes in cellular growth rate, the expression and subcellular distribution of U3 snRNA and one of its associated proteins, fibrillarin, were examined in mouse 3T6 fibroblasts. Altering serum concentrations produces changes in the ribosome content of the cell as reflected by total RNA levels. When exponentially growing 3T6 cells are induced to become quiescent by serum starvation, a significant downshift in U3 snRNA gene transcription occurs in parallel to a decrease in pre-rRNA synthesis. Serum stimulation results in an increase in the rate of synthesis of both U3 snRNA and pre-rRNA. However, U3 snRNA synthesis lags behind that of pre-rRNA. Furthermore, in serum-starved fibroblasts, a significant portion of the total cellular U3 snRNA appears in the cytoplasm. Following serum stimulation, a redistribution occurs and U3 snRNA is localized predominantly in the nucleolus at a level similar to that observed in exponentially growing cells. This redistribution is inhibited when RNA or protein synthesis is repressed in serum-stimulated fibroblasts by actinomycin D or cycloheximide. In contrast, the level and subcellular distribution of fibrillarin remain unchanged during serum starvation. These results suggest that during changes in ribosome production, distinct pools of U3 snRNPs exist within the cell.
AuthorsN Sienna, D E Larson, B H Sells
JournalExperimental cell research (Exp Cell Res) Vol. 227 Issue 1 Pg. 98-105 (Aug 25 1996) ISSN: 0014-4827 [Print] United States
PMID8806456 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
Chemical References
  • Chromosomal Proteins, Non-Histone
  • Protein Synthesis Inhibitors
  • Proteins
  • RNA Precursors
  • RNA, Small Nuclear
  • fibrillarin
  • Dactinomycin
  • RNA
  • Cycloheximide
Topics
  • Animals
  • Blood
  • Cell Division
  • Cell Line
  • Cell Nucleolus (chemistry)
  • Cell Nucleus (chemistry)
  • Chromosomal Proteins, Non-Histone (analysis)
  • Cycloheximide (pharmacology)
  • Cytoplasm (chemistry)
  • Dactinomycin (pharmacology)
  • Fibroblasts (chemistry, metabolism)
  • Mice
  • Protein Synthesis Inhibitors (pharmacology)
  • Proteins (analysis)
  • RNA (analysis, biosynthesis)
  • RNA Precursors (biosynthesis)
  • RNA, Small Nuclear (analysis, biosynthesis)
  • Ribosomes (chemistry)
  • Transcription, Genetic

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