Inducers of erythroleukemic differentiation cause messenger RNAs that lack poly(A)-binding protein to accumulate in translationally inactive, salt-labile 80 S ribosomal complexes.
Translation has an established role in the regulation of cell growth. Posttranslational modification of translation initiation and elongation factors or regulation of mRNA polyadenylation represent common means of regulating translation in response to mitogenic or developmental signals. Induced differentiation of Friend virus-transformed erythroleukemia cells is accompanied by a rapid decrease in the translation rate of these cells. Although inducers do not alter initiation factor modifications, characterization of their effect on mRNA translation provides evidence that this is mediated by the poly(A)-binding protein (PABP). Inducer exposure results in an increase in the amount of mRNA that sediments at 80 S and a decrease in the amount in polysomes. Although these 80 S ribosomes have characteristics previously attributed to "vacant ribosomal couples," including lability in 500 mM KCl and an inability to incorporate amino acids into protein, we provide evidence that these 80 S complexes are not vacant but contain mRNA that is stably bound to the 40 S subunit, whereas the 60 S subunit is dissociated from the complex by high salt. The absence of eukaryotic initiation factor 2 from these complexes suggests that translation has proceeded through subunit joining. Immunoblotting demonstrates that the mRNAs in these 80 S ribosomal complexes do not contain bound PABP and that this protein is found to be almost exclusively associated with translating polysomes. These data suggest that the PABP plays a role in the accumulation of these 80 S ribosomal.mRNA complexes and may facilitate the formation of translationally active salt-stable ribosomes.
Hensold
J O
JO
The University/Ireland Cancer Center, Department of Medicine, Case Western Reserve University, Cleveland, Ohio 44106, USA.
Barth-Baus
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Stratton
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D000596:Amino Acids / Q000378:metabolism; D000818:Animals; D000001:Calcimycin / Q000494:pharmacology; D002454:Cell Differentiation; D004121:Dimethyl Sulfoxide / Q000494:pharmacology; D015852:Eukaryotic Initiation Factor-2 / Q000032:analysis; D015973:Gene Expression Regulation, Leukemic; D004915:Leukemia, Erythroblastic, Acute / Q000235:genetics*; D051379:Mice; D039102:Poly(A)-Binding Proteins; D011132:Polyribosomes / Q000187:drug effects / Q000378:metabolism; D011189:Potassium Chloride / Q000494:pharmacology; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000378:metabolism*; D012334:RNA, Neoplasm / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000378:metabolism*; D012270:Ribosomes / Q000187:drug effects / Q000378:metabolism*; D013347:Subcellular Fractions / Q000378:metabolism; D014407:Tumor Cells, Cultured
D000596:Amino Acids; D015852:Eukaryotic Initiation Factor-2; D039102:Poly(A)-Binding Proteins; D012333:RNA, Messenger; D012334:RNA, Neoplasm; D016601:RNA-Binding Proteins; D000001:Calcimycin; D011189:Potassium Chloride; D004121:Dimethyl Sulfoxide