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|Title:||Isolation, characterization, and transcriptional autonomy of theout at first gene of Drosophila melanogaster|
|Author(s):||Bergstrom, David Eric|
|Doctoral Committee Chair(s):||Blackman, Ronald K.|
|Department / Program:||Biology|
|Degree Granting Institution:||University of Illinois at Urbana-Champaign|
|Abstract:||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.
Each oaf transcript contains two open reading frames separated by a single UGA termination codon. Conceptual translation of the coding region predicts a novel 37 kD protein (ORF 1) and a potential 54 kD readthrough protein (ORF 1 and ORF 2).
Remobilization of an enhancer trap transposon, E-32, inserted within the 5$\sp\prime$ untranslated region of oaf, has generated 6 recessive embryonic/first instar larval lethal alleles of oaf. Peripheral nervous system defects with reduced penetrance have been observed in two of the lines.
The lacZ gene within the E-32 transposon accurately reports a subset of the oaf transcription pattern. Surprisingly, lacZ expression is also detected in imaginal disks in patterns strikingly similar to the patterns of dpp transcription. Thus, it appears that the dpp disk region enhancers can activate lacZ, but not oaf, transcription in imaginal disks. A model of promoter specificity is presented to explain the distinct transcriptional patterns of oaf and dpp.
|Rights Information:||Copyright 1994 Bergstrom, David Eric|
|Date Available in IDEALS:||2011-05-07|
|Identifier in Online Catalog:||AAI9512300|