Tissue-specific expression in mouse P815 mastocytoma cells of the cloned rat α-subunit gene of the high-affinity receptor for immunoglobulin E

The high-affinity multisubunit receptor for IgE, Fcε{lunate}RI, is expressed in vivo in a tissue-specific manner, being found only on mast cells, basophils and epidermal Langerhans cells. The expression of the rat Fcε{lunate}RI α-subunit transcript has been examined here in the mouse mastocytoma cell line, P815, which does not express the endogenous mouse Fcε{lunate}RI α- or β-subunit transcripts. These studies indicate that an exogenously introduced rat α-subunit gene can be faithfully expressed in P815 cells, while no transcripts are produced in the mouse or rat B-lymphoid cell lines, SP2/0 and IR162, respectively. Therefore, in contrast to both B-cell lines, factors necessary for the tissue-specific expression of the α-subunit mRNA are present in the P815 cell line, yielding a correctly processed mRNA transcript; nevertheless, this tissue-specific expression is not rigorously species specific. Although the mechanism responsible for these observations is unknown, these results do imply that a specific cis-trans element interaction occurs between this transcriptional unit and factors in the P815 cells that control fidelity of tissue-specific mRNA synthesis and processing from the Fcε{lunate}RI α-subunit gene. Consequently, this reconstructed rat Fcε{lunate}RI α-subunit gene contains minimally sufficient cis elements for tissue-specific expression of mRNA, and so, the P815 cell line should be useful to define these requisite DNA cis elements of the gene, as well as the trans factors from P815 necessary for this process.