Gene structure and promoter function of murine Munc18-2, a nonneuronal exocytic Sec1 homolog

Sec1 family proteins are regulators of diverse exocytic processes, from yea st to man. Three mammalian homologues, Munc18-1, -2, and -3 have been descr ibed. We have studied the structure and expression of the mouse Munc18-2 ge ne. The Munc18-2 gene comprises 19 exons whose sizes range from 50 to 158 b p, with a total gene size of approximately 11 kb. A single transcript of 2. 1 kb is expressed in multiple non-neuronal murine tissues. Munc18-2 has a s triking resemblance to Munc18-1 in structure despite only 60% sequence iden tity, suggesting a recent gene duplication event. Analysis of the region up stream of the transcription start site shows that Munc18-2 has a TATA-less promoter, with a consensus initiator (Inr) sequence at the start of transcr iption, several Spl binding sites, and strong promoter activity in RBL-2H3 mast cells. The region from +5 to -430 is more active than +5 to -800, sugg esting upstream repressor elements. (C) 2000 Academic Press.