The human low affinity immunoglobulin G Fc receptor III-A and III-B genes. Molecular characterization of the promoter regions.
The human Fc receptor with low affinity for IgG (Fc gamma RIII, CD16) is encoded by two nearly identical genes, Fc gamma RIII-A and Fc gamma RIII-B, resulting in tissue-specific expression of alternative membrane-anchored isoforms. The transmembrane CD16 receptor forms a heteromeric structure with the Fc epsilon RI (gamma) and/or CD3 (zeta) subunits on the surface of activated monocytes/macrophages, NK cells, and a subset of T cells. The expression of the glycosylphosphatidylinositol-anchored CD16 isoform encoded by the Fc gamma RIII-B gene is restricted to polymorphonuclear leukocytes and can be induced by Me2SO differentiation of HL60 cells. We have isolated and sequenced genomic clones of the human Fc gamma RIII-A and Fc gamma RIII-B genes, located their transcription initiation sites, identified a different organization of their 5' regions, and demonstrated four distinct classes of Fc gamma RIII-A transcripts (a1-a4) compared with a single class of Fc gamma RIII-Bb1 transcripts. Both CD16 promoters (positions -198 to -10) lack the classical "TATA" positioning consensus sequence but confer transcriptional activity when coupled to the human lysozyme enhancer. Both promoters also display different tissue-specific transcriptional activities reflecting the expected gene expression of Fc gamma RIII-A and Fc gamma RIII-B in NK cells versus polymorphonuclear leukocytes. Within the -198/-10 fragments, the sequences of the two CD16 genes have been identified to differ in 10 positions. It is suggested that these nucleotide differences might contribute to cell type-specific transcription of Fc gamma RIII genes.
Department of Immunology, Hannover Medical School, Federal Republic of Germany.
J E
JE
Gessner
T
T
Grussenmeyer
W
W
Kolanus
R E
RE
Schmidt
D000595:Amino Acid Sequence; D001483:Base Sequence; D002460:Cell Line; D003001:Cloning, Molecular; D004247:DNA; D005786:Gene Expression Regulation; D006801:Humans; D007074:Immunoglobulin G / Q000378:metabolism*; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D017452:Receptors, IgG / Q000235:genetics* / Q000378:metabolism; D012689:Sequence Homology, Nucleic Acid; D014158:Transcription, Genetic
D007074:Immunoglobulin G; D017452:Receptors, IgG; D004247:DNA