2 DISTINCT REGIONS OF THE MOUSE-BETA FC-GAMMA-R GENE-CONTROL ITS TRANSCRIPTION

The low-affinity receptors for the Fc portion of IgG (Fc-gamma-RII and Fc-gamma-RIII) are born by most of the immunocompetent cells and mediate a wide spectrum of biological activities. Macrophages, mast cells and lymphocytes express the type II Fc-gamma-R whereas the type Ill Fc-gamma-R is expressed on macrophages, mast cells and NK cells. In mice, the beta Fc-gamma-R gene codes for Fc-gamma-RII and the a Fc-gamma-R gene codes for the ligand-binding Fc-gamma-RIII alpha-chain. We have previously demonstrated that the methylation of the 5' region of these genes control their expression. In the present paper, we investigate the role of two unmethylated regions of the beta gene, the promoter and the third intron, in the control of its transcription. We show, by using two cell lines representative of B and mast cells, that different promoter fragments determine, in these two cell types, the transcription of the beta Fc-gamma-R gene. The third intron of the beta Fc-gamma-R gene contains sequences, which, introduced upstream to homologous or heterologous promoter, inhibit the transcriptional activity of these promoter. Thus, in B cells and in mast cells, the transcription of the beta Fc-gamma-R gene is controlled by two distinct regions of the gene.