The ecdysone receptor (ScEcR-A) binds DNA puffs at the start of DNA amplification in Sciara coprophila
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The steroid hormone ecdysone induces DNA amplification and subsequent DNA puff formation in late fourth larval instar salivary gland polytene chromosomes of the fungus fly, Sciara coprophila. Previous in vitro studies on DNA puff II/9A in Sciara demonstrated that the ecdysone receptor (ScEcR-A) efficiently binds an ecdysone response element adjacent to the origin recognition complex binding site within the II/9A amplification origin, implying a role for ScEcR-A in amplification. Here, we extrapolate the molecular details from locus II/9A to the rest of the genome using immunofluorescence with a ScEcR-A-specific antibody. ScEcR-A binds all DNA puff sites just as amplification begins and persists throughout the processes of amplification, transcription, and puffing. Ecdysone injections into pre-amplification stage larvae prematurely induce both DNA amplification and ScEcR-A binding to DNA puff sites. These data are consistent with a direct role for ScEcR-A in DNA amplification.
Key Wordsecdysone ecdysone receptor Sciara coprophila DNA amplification immunofluorescence
Ecdysone response element
Origin recognition complex
Origin of replication
- Pol II
RNA polymerase II
G.M.L. was supported by a fellowship from the Agency for Science, Technology and Research (A*STAR), Singapore.
All experiments presented herein were performed in compliance with the current laws of the USA.
Conflict of Interest
Gerald M. Liew, Michael S. Foulk, and Susan A. Gerbi declare that they have no conflict of interest. This article does not contain any studies with human or vertebrate animal subjects performed by any of the authors.
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