Alternative splicing generates two distinct Eip28/29 gene transcripts in Drosophila Kc cells.

The Drosophila Eip28/29 gene encodes two primary translation products, ecdysone-inducible polypeptide (EIP) 28III and EIP 29III. When cells of the Kc cell line are treated with the steroid hormone ecdysone, the number of Eip28/29 transcripts and the synthesis of the various forms of EIP 28 and 29 increase rapidly. We have reported the sequence of the Eip28/29 gene and of its major transcript. Here we describe a minor or short-form transcript that is about 25% of the total Eip28/29 gene transcripts in both untreated and hormone-treated cells. This transcript is formed by the use of an alternative splice donor sequence 12 nucleotides upstream from the major donor site at the end of the second exon. Evidently the relative abundance of the two products is not hormonally regulated. The short form translation product should lack only an internal dibasic tetrapeptide. The long and short forms probably represent distinct mRNAs for EIP 28III and EIP 29III, respectively.