A highly conserved c-fms gene intronic element controls macrophage-specific and regulated expression.
The c-fms gene encodes the receptor for macrophage colony-stimulating factor-1. This gene is expressed selectively in the macrophage cell lineage. Previous studies have implicated sequences in intron 2 that control transcript elongation in tissue-specific and regulated expression of c-fms. Four macrophage-specific deoxyribonuclease I (DNase I)-hypersensitive sites (DHSs) were identified within mouse intron 2. Sequences of these DHSs were found to be highly conserved compared with those in the human gene. A 250-bp region we refer to as the fms intronic regulatory element (FIRE), which is even more highly conserved than the c-fms proximal promoter, contains many consensus binding sites for macrophage-expressed transcription factors including Sp1, PU.1, and C/EBP. FIRE was found to act as a macrophage-specific enhancer and as a promoter with an antisense orientation preference in transient transfections. In stable transfections of the macrophage line RAW264, as well as in clones selected for high- and low-level c-fms mRNA expression, the presence of intron 2 increased the frequency and level of expression of reporter genes compared with those attained using the promoter alone. Removal of FIRE abolished reporter gene expression, revealing a suppressive activity in the remaining intronic sequences. Hence, FIRE is shown to be a key regulatory element in the fms gene.
Himes
S R
SR
Institute for Molecular Bioscience, University of Queensland, Brisbane 4072, Australia.
Tagoh
H
H
Goonetilleke
N
N
Sasmono
T
T
Oceandy
D
D
Clark
R
R
Bonifer
C
C
Hume
D A
DA
D016475:3T3 Cells / Q000378:metabolism; D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D003850:Deoxyribonuclease I / Q000378:metabolism; D004742:Enhancer Elements, Genetic / Q000235:genetics*; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation / Q000235:genetics*; D017930:Genes, Reporter; D016236:Genes, fms / Q000235:genetics*; D006801:Humans; D007438:Introns / Q000235:genetics*; D008156:Luciferases / Q000096:biosynthesis / Q000235:genetics; D008264:Macrophages / Q000378:metabolism*; D051379:Mice; D008969:Molecular Sequence Data; D020319:Oligodeoxyribonucleotides, Antisense / Q000235:genetics; D020411:Oligonucleotide Array Sequence Analysis; D011401:Promoter Regions, Genetic / Q000235:genetics*; D012333:RNA, Messenger / Q000096:biosynthesis; D016186:Receptor, Macrophage Colony-Stimulating Factor / Q000096:biosynthesis*; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D012045:Regulatory Sequences, Nucleic Acid; D016415:Sequence Alignment; D012689:Sequence Homology, Nucleic Acid; D014157:Transcription Factors / Q000378:metabolism; D014162:Transfection
D020319:Oligodeoxyribonucleotides, Antisense; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; D008156:Luciferases; D016186:Receptor, Macrophage Colony-Stimulating Factor; D003850:Deoxyribonuclease I