ANALYSIS OF GENE-EXPRESSION IN REGENERATING RAT-LIVER BY HYBRIDIZATION OF NUCLEAR AND CYTOPLASMIC-RNA WITH DNA-CYTOPLASMIC

  • 1 January 1977
    • journal article
    • research article
    • Vol. 37  (1) , 118-127
Abstract
To determine whether massive gene activation occurs in rat liver following partial hepatectomy, DNA-RNA hybridization-saturation and RNA depletion experiments were performed. RNA was extracted from whole cells, nuclei, postmitochondrial extracts, and polysomes obtained from livers of normal, sham-operated and partially hepatectomized rats. The purified RNA was labeled with [3H]dimethyl sulfate in vitro and hybridized with nuclear DNA under conditions in which only repetitive sequence transcripts form hybrids with DNA. Nuclear RNA was also labeled with [32P]phosphoric acid in vivo. For whole-cell RNA, the saturation levels obtained in the hybridization reaction are the same regardless of the source of RNA used (normal, sham-operated, or partially hepatectomized rats). No differences in the saturation levels were found when liver nuclear RNA from these 3 groups of animals were used. The concentration of nuclear RNA from 6-h regenerating liver necessary to saturate the DNA is slightly higher than that of nuclear RNA obtained from normal rat liver. Cytoplasmic RNA from 6-h regenerating liver saturates the DNA at a much lower concentration than that required for RNA from normal or sham-operated rats. For repetitive sequence transcripts, massive derepression of the genome does not occur at the early stages of liver regeneration. The alterations detected primarily reflect changes in RNA concentrations rather than qualitative alterations in gene expression. Increased transport of repetitive sequence transcripts from nucleus to cytoplasm appears to take place in regenerating liver.

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