Isolation, characterization, and transcriptional autonomy of theout at first gene of Drosophila melanogaster
The mechanisms that constrain enhancers to interact only with their own promoter, and not with the promoters of adjacent transcription units, are poorly understood. To test if, and how, a transcription unit 3$\sp\prime$ of the enhancer rich decapentaplegic (dpp) disk region might remain transcriptionally autonomous of disk region influence, I isolated and characterized the out at first gene (oaf, previously named l(2)ND1), the first transcription unit 3$\sp\prime$ of the disk region. I have found that oaf encodes at least three classes of transcripts (of around 3.3, 2.5, and 1.8 kb) initiating at a common TATA-less promoter and ending at one of three alternate sites of polyadenylation. Transcription products of oaf consist of a maternal component (primarily the 2.5 and 1.8 kb RNAs) uniformly distributed throughout the early embryo, and a zygotic component (primarily the 3.3 kb RNA) expressed in small clusters of cells in the segments of germ band extended embryos and in the brain and nerve cord of older embryos. oaf transcripts are also present in the developing gonads and within the nurse cells of adult female ovaries. With the possible exception of the segmental expression, oaf transcription is distinct from that of dpp. In particular, oaf is not observed in imaginal disks showing that the relatively near dpp disk region enhancers have no effect on oaf transcription.
University of Illinois - Urbana-Champaign
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University of Illinois at Urbana-Champaign