CCAAT displacement protein (CDP/cut) recognizes a silencer element within the lactoferrin gene promoter.
Expression of neutrophil secondary granule protein (SGP) genes is coordinately regulated at the transcriptional level, and is disrupted in specific granule deficiency and leukemia. We analyzed the regulation of SGP gene expression by luciferase reporter gene assays using the lactoferrin (LF) promoter. Reporter plasmids were transiently transfected into non-LF-expressing hematopoietic cell lines. Luciferase activity was detected from reporter plasmids containing base-pair (bp) -387 to bp -726 of the LF promoter, but not in a -916-bp plasmid. Transfection of a -916-bp plasmid into a LF-expressing cell line resulted in abrogation of the silencing effect. Sequence analysis of this region revealed three eight-bp repetitive elements, the deletion of which restored wild-type levels of luciferase activity to the -916-bp reporter plasmid. Electrophoretic mobility shift assay and UV cross-linking analysis identified a protein of approximately 180 kD that binds to this region in non-LF-expressing cells but not in LF-expressing cells. This protein was identified to be the CCAAT displacement protein (CDP/cut). CDP/cut has been shown to downregulate expression of gp91-phox, a gene expressed relatively early in the myeloid lineage. Our observations suggest that the binding of CDP/cut to the LF silencer element serves to suppress basal promoter activity of the LF gene in non-LF-expressing cells. Furthermore, overexpression of CDP/cut in cultured myeloid stem cells blocks LF expression upon granulocyte colony-stimulating factor-induced neutrophil maturation without blocking phenotypic maturation. This block in LF expression may be due, in part, to the persistence of CDP/cut binding to the LF silencer element.
Khanna-Gupta
A
A
Department of Internal Medicine, Yale University School of Medicine, New Haven, CT 06510, USA.
Zibello
T
T
Kolla
S
S
Neufeld
E J
EJ
Berliner
N
N
D001483:Base Sequence; D005786:Gene Expression Regulation; D015973:Gene Expression Regulation, Leukemic; D017930:Genes, Reporter; D016179:Granulocyte Colony-Stimulating Factor / Q000494:pharmacology; D018398:Homeodomain Proteins; D006801:Humans; D007781:Lactoferrin / Q000235:genetics*; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000494:pharmacology*; D011401:Promoter Regions, Genetic; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D012045:Regulatory Sequences, Nucleic Acid; D012097:Repressor Proteins / Q000494:pharmacology*; D017384:Sequence Deletion; D014157:Transcription Factors; D014162:Transfection; D014407:Tumor Cells, Cultured
C080632:CUX1 protein, human; D018398:Homeodomain Proteins; D009687:Nuclear Proteins; D011993:Recombinant Fusion Proteins; D012097:Repressor Proteins; D014157:Transcription Factors; D016179:Granulocyte Colony-Stimulating Factor; D007781:Lactoferrin