EM analysis of Drosophila chorion genes: Amplification, transcription termination and RNA splicing

We have used the electron microscope to examine ultrastructurally several events occuring during the biogenesis of two very abundant chorion (eggshell) mRNA molecules in the follicle cells of Drosophila melanogaster—namely, selective gene amplification, transcription initiation and termination, and...

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Bibliographic Details
Published in:Electron microscopy reviews 1991, Vol.4 (1), p.111-128
Main Authors: Osheim, Yvonne N., Beyer, Ann L.
Format: Article
Language:English
Subjects:
Animals
Biological and medical sciences
Chorion - metabolism
Chorion - ultrastructure
Drosophila melanogaster - genetics
Drosophila melanogaster - ultrastructure
Female
Fundamental and applied biological sciences. Psychology
Gene Amplification
Microscopy, Electron
Molecular and cellular biology
Molecular genetics
RNA Splicing
Transcription, Genetic
Transcription. Transcription factor. Splicing. Rna processing
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Summary:We have used the electron microscope to examine ultrastructurally several events occuring during the biogenesis of two very abundant chorion (eggshell) mRNA molecules in the follicle cells of Drosophila melanogaster—namely, selective gene amplification, transcription initiation and termination, and RNA rocessing. We find that the highly transcribed s36 and s38 genes are positioned in the central region of large, multi-forked amplified DNA structures. Transcript morphology is consistent with the known presence of a small intron at the 5' end of each gene. mature transcripts are associated with spliceosomes, demonstrating that splice site selection occurs co-transcriptionally but that splicing is completed after transcript release from the template. We have also mapped the termination sites for the genes. The two genes exhibit efficient termination very near their poly(A) sites—within a 210 bp region for s36 and a 360 bp region for s38.
ISSN:0892-0354
DOI:10.1016/0892-0354(91)90018-8