ALTERNATIVE RNA OF EPSILON-TRANSCRIPTS PRODUCES MESSENGER-RNAS ENCODING 2 MEMBRANE AND 4 SECRETED IGE ISOFORMS

We elucidated a series of alternatively spliced human epsilon mRNAs by employing a human epsilon-specific RT-PCR strategy. Two mRNA isoforms provide for the expression of distinct membrane IgE proteins, the com mon form of which contains a novel 56-amino-acid sequence after the la st epsilon constant-region domain. Other mRNAs encode, in addition to the classic secreted epsilon chain, at least three novel epsilon secre ted proteins that lack a transmembrane domain and possess distinctive C-terminal features. Furthermore, the expression of these epsilon mRNA isoforms is differentially regulated by stimuli such as interleukin-1 0, Fc epsilon RII cross-linking and aromatic hydrocarbons found in die sel exhaust.