The antiapoptotic gene mcl-1 is up-regulated by the phosphatidylinositol 3-kinase/Akt signaling pathway through a transcription factor complex containing CREB.
mcl-1 is an immediate-early gene activated by the granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin 3 (IL-3) signaling pathways and plays an important role in the viability response of these cytokines. In this study, we demonstrated that cytokine stimulation of mcl-1 mRNA and protein expression were attenuated by pretreatment of cells with phosphatidylinositol 3-kinase (PI3-K) inhibitors. Reporter gene assays further showed that the PI3-K/Akt signaling pathway was involved in IL-3 activation of mcl-1 gene transcription. Analysis of the mcl-1 promoter revealed that both promoter elements, SIE at position -87 and CRE-2 at -70, contribute to IL-3 stimulation of mcl-1 gene expression. Although either the SIE site or the CRE-2 site alone was sufficient to confer IL-3 inducibility on a heterologous promoter, only IL-3 activation of the CRE-2 reporter was mediated via the PI3-K/Akt pathway. The SIE binding activity was constitutively high in cells deprived of or stimulated by IL-3. In contrast, the CRE-2 binding activity was low in cytokine-starved cells and was strongly induced within 1 h following cytokine treatment of cells. In addition, cytokine induction of the CRE-2 but not of the SIE binding activity was dependent on activation of the PI3-K/Akt signaling pathway. Lastly, we showed that CREB was one component of the CRE-2 binding complex and played a role in IL-3 activation of the mcl-1 reporter gene. Taken together, our results suggest that both PI3-K/Akt-dependent and -independent pathways contribute to the IL-3 activation of mcl-1 gene expression. Activation of mcl-1 by the PI3-K/Akt-dependent pathway is through a transcription factor complex containing CREB.
Wang
J M
JM
Graduate Institute of Life Science, National Defense Medical School, Taipei, Taiwan, Republic of China.
Chao
J R
JR
Chen
W
W
Kuo
M L
ML
Yen
J J
JJ
Yang-Yen
H F
HF
D017209:Apoptosis / Q000235:genetics*; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D002460:Cell Line; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism; D017931:DNA Primers / Q000235:genetics; D017781:Genes, Immediate-Early; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000494:pharmacology; D006801:Humans; D007377:Interleukin-3 / Q000494:pharmacology; D046911:Macromolecular Substances; D008969:Molecular Sequence Data; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D009363:Neoplasm Proteins / Q000235:genetics* / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D014157:Transcription Factors / Q000378:metabolism*; D015854:Up-Regulation
D017362:Cyclic AMP Response Element-Binding Protein; D017931:DNA Primers; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D007377:Interleukin-3; D046911:Macromolecular Substances; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D009363:Neoplasm Proteins; D019869:Phosphatidylinositol 3-Kinases; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger; D014157:Transcription Factors; C494918:AKT1 protein, human