Evaluation of the role of Ap1-like proteins in the enhanced apolipoprotein E gene transcription accompanying phorbol ester induced macrophage differentiation.
Differentiation of THP1 monocytes to a macrophage phenotype is accompanied by increased apolipoprotein E gene transcription. Using transfection analysis with 5' deletion mutations of the 5' control region of the apo E gene in THP1 cells, we show that the -651 to +86 chloramphenicol acetyltransferase (CAT) construct is efficiently expressed in the monocyte; as has been reported for other cell types. Further, we found that an 176 bp region between -623 to -447 was required for the induction of apolipoprotein E gene transcription during 12-O-tetradecanoylphorbol-13-acetate-induced differentiation of monocytes to macrophages. Gel-retardation patterns of the apolipoprotein E promoter region using nuclear extracts from differentiated or undifferentiated THP1 cells revealed altered binding of Ap1-like nuclear factor/s to the -620 to -583 bp region after macrophage differentiation. Mutation of an Ap1 element at position -602 abolished specific binding of Ap1-like proteins to the -620 to -583 bp fragment of the apo E gene and significantly reduced expression of a -623 to +86 apo E-CAT construct during differentiation. These data indicate that differentiation-related expression of the apolipoprotein E gene following phorbol ester stimulation is transduced by gene elements between -623 and -447. Furthermore, the data indicate that transcriptional activation of the apo E gene during macrophage differentiation is associated with induction of Ap1-like proteins which bind to the Ap1 response element present at -602 in the apolipoprotein E gene and importantly contribute to enhanced gene expression.
Department of Medicine and Biochemistry, Rush Medical College, Chicago, IL 60612.
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Basheeruddin
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Rechtoris
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Mazzone
D033961:Adaptor Protein Complex 1; D033965:Adaptor Protein Complex alpha Subunits; D033942:Adaptor Proteins, Vesicular Transport; D001057:Apolipoproteins E / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D002454:Cell Differentiation; D005786:Gene Expression Regulation; D006801:Humans; D008264:Macrophages / Q000187:drug effects* / Q000378:metabolism; D008969:Molecular Sequence Data; D010703:Phorbol Esters / Q000494:pharmacology; D011506:Proteins / Q000235:genetics*; D014158:Transcription, Genetic; D014162:Transfection; D014407:Tumor Cells, Cultured
D033961:Adaptor Protein Complex 1; D033965:Adaptor Protein Complex alpha Subunits; D033942:Adaptor Proteins, Vesicular Transport; D001057:Apolipoproteins E; D010703:Phorbol Esters; D011506:Proteins