Involvement of the transcription factor NF-IL6 in phorbol ester induction of P-glycoprotein in U937 cells.
Previously, we showed that the nuclear factor NF-IL6 binds and trans-activates the promoter of the human multidrug resistance gene (MDR1) encoding P-glycoprotein (N. J. Combates et al., J. Biol. Chem., 269: 29715-29719, 1994). In this study, we investigated the physiological relevance of MDR1 gene regulation by NF-IL6 in response to PMA (phorbol 12-myristate 13-acetate)-induced differentiation. Treatment of U937 cells, a human promonocytic cell line, with PMA induced their differentiation along the macrophage/monocytic cell lineage. The cellular changes were found to be accompanied by an increase in P-glycoprotein expression at the cell surface. PMA treatment of U937 cells also resulted in the synthesis of the three forms of NF-IL6 and an enhanced DNA binding activity of nuclear extracts to a probe derived from the MDR1 promoter. The majority of the DNA-protein complex could be supershifted by an NF-IL6 reactive antibody but not by antibodies for CAAT/enhancer binding protein alpha and delta, c-fos, or c-jun. Furthermore, transient transfection studies demonstrated that PMA enhanced the activity of a MDR1 promoter-driven luciferase gene construct to a greater extent as compared with the activity of a reporter construct containing mutations within the NF-IL6 responsive element. These results indicate a correlation between NF-IL6 gene expression and the regulation of the MDR1 gene. Furthermore, these observations also suggest that P-glycoprotein expression is part of the macrophage differentiation process.
Combates
N J
NJ
Oncology Research Program, Sandoz Research Institute, East Hanover, New Jersey 07936, USA.
Kwon
P O
PO
Rzepka
R W
RW
Cohen
D
D
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000096:biosynthesis* / Q000235:genetics* / Q000502:physiology; D022762:CCAAT-Enhancer-Binding Proteins; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000378:metabolism / Q000502:physiology*; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology; D019450:Genes, MDR / Q000187:drug effects / Q000502:physiology; D006801:Humans; D009687:Nuclear Proteins / Q000378:metabolism / Q000502:physiology*; D011401:Promoter Regions, Genetic / Q000187:drug effects / Q000235:genetics; D013755:Tetradecanoylphorbol Acetate / Q000378:metabolism / Q000494:pharmacology*; D014157:Transcription Factors / Q000502:physiology*; D014162:Transfection; D014407:Tumor Cells, Cultured
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D022762:CCAAT-Enhancer-Binding Proteins; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D014157:Transcription Factors; D013755:Tetradecanoylphorbol Acetate