CCAAT displacement protein as a repressor of the myelomonocytic-specific gp91-phox gene promoter.
The cytochrome b heavy chain (gp91-phox) is expressed exclusively in terminally differentiating myelomonocytic cells. The human gp91-phox gene spans approximately 30 kilobases, and is divided into 13 exons. A ubiquitous factor that is indistinguishable from the CCAAT-binding factor CP1 interacts in vitro with the distal gp91-phox promoter CCAAT box motif. CP1 binding is prevented, however, by a CCAAT displacement protein (CDP) that binds to the region surrounding the CCAAT box. CDP DNA-binding activity is found in nuclear extracts prepared from cells in which the endogenous gp91-phox gene is transcriptionally inactive, but is absent or reduced in expressing cells, consistent with CDP functioning as a repressor of gp91-phox transcription. Introduction of gp91-phox promoter/reporter constructs into nonexpressing cells yields significantly less expression than that produced by the parental reporter vector alone. The reduction in expression is relieved when the CDP/CP1-binding site is removed from the gp91-phox promoter, confirming that it is a target for repression. No derepression is observed if the CP1-binding site is selectively mutated. Derepression of expression exhibited upon deletion of the CDP/CP1-binding site suggests that, in addition to blocking the interaction of the CCAAT-binding factor with the gp91-phox promoter, CDP may also repress transcription mediated through a distinct cis-element(s). We propose that down-regulation of CDP DNA-binding activity is a necessary step in the induction of myelomonocytic-specific expression of the gp91-phox gene.
Skalnik
D G
DG
Division of Hematology and Oncology, Children's Hospital, Dana Farber Cancer Institute, Boston, Massachusetts.
Strauss
E C
EC
Orkin
S H
SH
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D022762:CCAAT-Enhancer-Binding Proteins; D003001:Cloning, Molecular; D003573:Cytochrome b Group / Q000235:genetics*; D004247:DNA; D004268:DNA-Binding Proteins / Q000378:metabolism*; D003850:Deoxyribonuclease I / Q000378:metabolism; D005786:Gene Expression Regulation; D006801:Humans; D015477:Leukemia, Myelomonocytic, Chronic; D008745:Methylation; D008969:Molecular Sequence Data; D010586:Phagocytes / Q000378:metabolism; D011401:Promoter Regions, Genetic; D012097:Repressor Proteins / Q000378:metabolism*; D012617:Sea Urchins; D014407:Tumor Cells, Cultured
D022762:CCAAT-Enhancer-Binding Proteins; D003573:Cytochrome b Group; D004268:DNA-Binding Proteins; D012097:Repressor Proteins; D004247:DNA; D003850:Deoxyribonuclease I