B-Myb-dependent regulation of c-Myc expression by cytosolic phospholipase A2.
Cytosolic phospholipase A(2) (cPLA(2)) cleaves membrane phospholipids to release arachidonic acid, initiating lipoxygenase and cyclooxygenase pathways. Mice lacking a gene for cPLA(2) suggested important roles of the protein in allergic responses, fertility, and neural cell death. Here we show that cPLA(2) negatively regulates c-Myc expression in a B-Myb-dependent manner. Overexpression ... of cPLA(2) protein but not a mutant cPLA(2) protein that lacks in vitro binding ability with B-Myb inhibits B-Myb-dependent c-myc gene expression. The inhibition was associated with physical interaction of B-Myb protein with cPLA(2) both in the cytoplasm and the nucleus. Binding site analysis demonstrated that both the N and C termini of cPLA(2) interact with B-Myb. Macrophage colony stimulating factor (MCSF) stimulated cPLA(2) redistribution into the nucleus and also association with B-Myb in human monocytes. Importantly, macrophages from mice with a disrupted cPLA(2) gene demonstrated significantly increased levels of c-Myc protein in the nucleus compared with cells from the wild-type mice, whereas B-Myb levels were similar in the cells from the cPLA(2)(+/+) and cPLA(2)(-/-) mice. Moreover, an introduction of cPLA(2) into cPLA(2)(-/-) mouse macrophages resulted in decreased c-Myc protein levels, and an inhibition of cPLA(2) expression by small interfering RNAs or antisense RNA increased the c-myc transcription in macrophage colony stimulating factor-activated human monocytes. These findings provide new insights into the function of cPLA(2) in B-Myb-dependent gene expression.
Mesh Terms:
Animals, Arachidonic Acid, Binding Sites, Blotting, Western, Cell Cycle Proteins, Cell Death, Cell Line, Cell Nucleus, Cytoplasm, DNA Damage, DNA-Binding Proteins, Gene Expression Regulation, Genes, Reporter, Humans, Hydrogen Peroxide, Macrophage Colony-Stimulating Factor, Macrophages, Mice, Mice, Transgenic, Microscopy, Confocal, Microscopy, Fluorescence, Monocytes, Phospholipases A, Phospholipases A2, Plasmids, Precipitin Tests, Protein Binding, Protein Structure, Tertiary, Proto-Oncogene Proteins c-myc, RNA, Antisense, RNA, Small Interfering, Reverse Transcriptase Polymerase Chain Reaction, Subcellular Fractions, Time Factors, Trans-Activators, Ultraviolet Rays, Up-Regulation
Animals, Arachidonic Acid, Binding Sites, Blotting, Western, Cell Cycle Proteins, Cell Death, Cell Line, Cell Nucleus, Cytoplasm, DNA Damage, DNA-Binding Proteins, Gene Expression Regulation, Genes, Reporter, Humans, Hydrogen Peroxide, Macrophage Colony-Stimulating Factor, Macrophages, Mice, Mice, Transgenic, Microscopy, Confocal, Microscopy, Fluorescence, Monocytes, Phospholipases A, Phospholipases A2, Plasmids, Precipitin Tests, Protein Binding, Protein Structure, Tertiary, Proto-Oncogene Proteins c-myc, RNA, Antisense, RNA, Small Interfering, Reverse Transcriptase Polymerase Chain Reaction, Subcellular Fractions, Time Factors, Trans-Activators, Ultraviolet Rays, Up-Regulation
J. Biol. Chem.
Date: Apr. 23, 2004
PubMed ID: 14769798
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