[HTML][HTML] Nuclear retention of the induced mRNA following amino acid-dependent transcriptional regulation of mammalian ribosomal proteins L17 and S25

RO Laine, NF Shay, MS Kilberg - Journal of Biological Chemistry, 1994 - Elsevier
RO Laine, NF Shay, MS Kilberg
Journal of Biological Chemistry, 1994Elsevier
An amino acid starvation-induced mRNA, increased up to 4-fold in the absence of amino
acids, was identified previously as rat 60 S subunit ribosomal protein L17. The data
presented here demonstrate that among ribosomal proteins, L17, as well as the smaller
subunit ribosomal protein S25, are uniquely regulated by amino acid deprivation of cells; the
increase in L17 and S25 mRNA content in response to substrate starvation is not shared by
the 11 other ribosomal proteins tested. When rat Fao hepatoma cells were incubated in the …
An amino acid starvation-induced mRNA, increased up to 4-fold in the absence of amino acids, was identified previously as rat 60 S subunit ribosomal protein L17. The data presented here demonstrate that among ribosomal proteins, L17, as well as the smaller subunit ribosomal protein S25, are uniquely regulated by amino acid deprivation of cells; the increase in L17 and S25 mRNA content in response to substrate starvation is not shared by the 11 other ribosomal proteins tested. When rat Fao hepatoma cells were incubated in the presence of actinomycin D, the L17 mRNA level decayed below the basal level, regardless of medium amino acid content, and nuclear run-off assays confirmed that nutrient starvation leads to enhanced transcription of the L17 ribosomal protein gene. Likewise, the induction of S25 mRNA also was prevented in the presence of actinomycin D. Furthermore, the induction of L17 and S25 mRNA content was blocked by cycloheximide, demonstrating the requirement for a newly synthesized protein in the signaling pathway. Northern analysis with RNA isolated from cytoplasmic, polysomal, and nuclear enriched fractions indicated that the starvation-dependent increase in the S25 and L17 mRNAs is retained within the nucleus and not is available for translation. Amino acid refeeding of the cells caused the translocation of the stored nuclear mRNAs to the polysomal fraction.
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