Phorbol ester-stimulated phosphorylation of PU.1: association with leukemic cell growth inhibition.
PU.1, a member of the ets transcription factor family, has been previously shown to be necessary for tetradecanoylphorbol-13 acetate (TPA)-induced U937 leukemic cell maturation. We examined the effects of TPA on PU.1 content and PU.1 DNA binding activity in U937 cells. Unstimulated cells expressed PU.1 mRNA transcripts and TPA did not increase these levels. However, TPA treatment induced phosphorylation of PU.1. Gel-shift analysis using a labeled PU.1 oligomer showed that TPA induced a unique PU.1 binding activity. This binding activity was phosphorylation-dependent, as indicated by the ability of phosphatase treatment to abolish its detection. The PU.1 binding activity was generated at TPA-13 concentrations stimulating growth arrest and was blocked by the PKC inhibitor GF109203X, which antagonized TPA-induced growth inhibition. Bryostatin 1, another protein kinase C activator, induced only a modest degree of U937 growth inhibition and antagonized TPA-stimulated growth arrest. Bryostatin 1 was unable to induce this TPA-generated PU.1 binding activity. High bryostatin 1 concentrations inhibited generation of this TPA-induced band shift. These data suggest that TPA-induced growth inhibition is associated with phosphorylation of PU.1 and generation of a unique PU.1 binding activity.
Carey
J O
JO
Department of Medicine, East Carolina University School of Medicine, Greenville, NC 27858, USA.
Posekany
K J
KJ
deVente
J E
JE
Pettit
G R
GR
Ways
D K
DK
D001483:Base Sequence; D054713:Bryostatins; D002454:Cell Differentiation / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D004273:DNA, Neoplasm / Q000378:metabolism; D004742:Enhancer Elements, Genetic; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015973:Gene Expression Regulation, Leukemic / Q000187:drug effects*; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D007783:Lactones / Q000494:pharmacology; D016403:Lymphoma, Large B-Cell, Diffuse / Q000473:pathology; D018942:Macrolides; D008301:Maleimides / Q000494:pharmacology; D008969:Molecular Sequence Data; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D011485:Protein Binding / Q000187:drug effects; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000502:physiology; D011499:Protein Processing, Post-Translational / Q000187:drug effects*; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D011519:Proto-Oncogenes; D012333:RNA, Messenger / Q000096:biosynthesis; D012334:RNA, Neoplasm / Q000096:biosynthesis; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D015534:Trans-Activators; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic / Q000187:drug effects; D014407:Tumor Cells, Cultured / Q000187:drug effects; D000099232:Proto-Oncogene Protein Spi-1
D054713:Bryostatins; D004273:DNA, Neoplasm; D004791:Enzyme Inhibitors; D007211:Indoles; D007783:Lactones; D018942:Macrolides; D008301:Maleimides; D009363:Neoplasm Proteins; D011493:Protein Kinase C; D011518:Proto-Oncogene Proteins; D012333:RNA, Messenger; D012334:RNA, Neoplasm; D013755:Tetradecanoylphorbol Acetate; D015534:Trans-Activators; D014157:Transcription Factors; D000099232:Proto-Oncogene Protein Spi-1; C046785:bryostatin 1; C070515:bisindolylmaleimide I