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.
Tashiro
Shigeki
S
Department of Radiology and Cancer Biology, Nagasaki University School of Dentistry, Nagasaki 852-8588, Japan.
Sumi
Tadateru
T
Uozumi
Naonori
N
Shimizu
Takao
T
Nakamura
Takashi
T
D000818:Animals; D016718:Arachidonic Acid / Q000378:metabolism; D001665:Binding Sites; D015153:Blotting, Western; D018797:Cell Cycle Proteins; D016923:Cell Death; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D004249:DNA Damage; D004268:DNA-Binding Proteins / Q000378:metabolism*; D005786:Gene Expression Regulation; D017930:Genes, Reporter; D006801:Humans; D006861:Hydrogen Peroxide / Q000737:chemistry; D016173:Macrophage Colony-Stimulating Factor / Q000378:metabolism; D008264:Macrophages / Q000378:metabolism; D051379:Mice; D008822:Mice, Transgenic; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D009000:Monocytes / Q000378:metabolism; D010741:Phospholipases A / Q000502:physiology*; D054467:Phospholipases A2; D010957:Plasmids / Q000378:metabolism; D011233:Precipitin Tests; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D016271:Proto-Oncogene Proteins c-myc / Q000096:biosynthesis*; D016372:RNA, Antisense / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013347:Subcellular Fractions; D013997:Time Factors; D015534:Trans-Activators / Q000378:metabolism*; D014466:Ultraviolet Rays; D015854:Up-Regulation
D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; C064352:MYBL2 protein, human; C499306:Mybl2 protein, mouse; D016271:Proto-Oncogene Proteins c-myc; D016372:RNA, Antisense; D034741:RNA, Small Interfering; D015534:Trans-Activators; D016718:Arachidonic Acid; D016173:Macrophage Colony-Stimulating Factor; D006861:Hydrogen Peroxide; D010741:Phospholipases A; D054467:Phospholipases A2