Splicing precedes polyadenylation during Drosophila E74A transcription.
The E74 gene is one of a small set of early genes induced by the steroid hormone ecdysone at the onset of metamorphosis in the fruit fly, Drosophila melanogaster. This complex gene directs the synthesis of a 60-kilobase (kb) primary transcript that is spliced to form the 6-kb E74A mRNA. In a previous study, we found that ecdysone directly activates the E74A promoter and determined that RNA polymerase II transcribes this gene at a rate of approximately 1.1 kb/min. This elongation rate accounts for most of the 1-hour delay seen between the addition of ecdysone and the appearance of cytoplasmic E74A mRNA (C. S. Thummel, K. C. Burtis, and D. S. Hogness, Cell 61:101-111, 1990). We show here that nascent E74A transcripts are spliced, and we propose a model for the order of that splicing. This study provides, for the first time, direct biochemical evidence for splicing of a low-abundance cellular RNA before transcription termination and polyadenylation.
LeMaire
M F
MF
Department of Human Genetics, Howard Hughes Medical Institute, University of Utah Medical Center, Salt Lake City 84132.
Thummel
C S
CS
D000818:Animals; D004331:Drosophila melanogaster / Q000235:genetics*; D007700:Kinetics; D011061:Poly A / Q000235:genetics*; D011401:Promoter Regions, Genetic; D012319:RNA Polymerase II / Q000378:metabolism*; D015347:RNA Probes; D012326:RNA Splicing; D012333:RNA, Messenger / Q000235:genetics*; D014158:Transcription, Genetic
D015347:RNA Probes; D012333:RNA, Messenger; D011061:Poly A; D012319:RNA Polymerase II