Regulation of c-myc mRNA decay in vitro by a phorbol ester-inducible, ribosome-associated component in differentiating megakaryoblasts.
The K562 leukemia cell line is bipotential for erythroid and megakaryoblastic differentiation. The phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA) activates a genetic program of gene expression in these cells leading to their differentiation into megakaryoblasts, a platelet precursor. Thus, K562 cells offer a means to examine early changes in gene expression necessary for megakaryoblastic commitment and differentiation. An essential requirement for differentiation of many hematopoietic cell types is the down-regulation of c-myc expression, because its constitutive expression blocks differentiation. TPA-induced differentiation of K562 cells causes rapid down-regulation of c-myc expression, due in part to an mRNA decay rate that is 4-fold faster compared with dividing cells. A cell-free mRNA decay system reconstitutes TPA-induced destabilization of c-myc mRNA, but it requires at least two components for reconstitution. One component fractionates to the post-ribosomal supernatant from either untreated or treated cells. This component is sensitive to cycloheximide and micrococcal nuclease. The other component is polysome-associated and is induced or activated by TPA. Although in dividing cells c-myc mRNA decays via a sequential pathway involving removal of the poly(A) tract followed by degradation of the mRNA body, TPA activates a deadenylation-independent pathway. The cell-free mRNA decay system reconstitutes this alternate decay pathway as well.
Department of Molecular Genetics and Microbiology, University of Medicine & Dentistry of New Jersey, Robert Wood Johnson Medical School, Piscataway, New Jersey 08854, USA. brewerga@umdnj.edu
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D002352:Carrier Proteins / Q000032:analysis; D002454:Cell Differentiation / Q000187:drug effects; D003513:Cycloheximide / Q000494:pharmacology; D015536:Down-Regulation; D005786:Gene Expression Regulation; D016259:Genes, myc; D006801:Humans; D020014:K562 Cells; D008533:Megakaryocytes / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism*; D012270:Ribosomes / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*
D002352:Carrier Proteins; D012333:RNA, Messenger; D003513:Cycloheximide; D013755:Tetradecanoylphorbol Acetate