Isolation and characterization of the ecdysone receptor and its heterodimeric partner ultraspiracle through development in Sciara coprophila
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Regulation of DNA replication is critical, and loss of control can lead to DNA amplification. Naturally occurring, developmentally regulated DNA amplification occurs in the DNA puffs of the late larval salivary gland giant polytene chromosomes in the fungus fly, Sciara coprophila. The steroid hormone ecdysone induces DNA amplification in Sciara, and the amplification origin of DNA puff II/9A contains a putative binding site for the ecdysone receptor (EcR). We report here the isolation, cloning, and characterizing of two ecdysone receptor isoforms in Sciara (ScEcR-A and ScEcR-B) and the heterodimeric partner, ultraspiracle (ScUSP). ScEcR-A is the predominant isoform in larval tissues and ScEcR-B in adult tissues, contrary to the pattern in Drosophila. Moreover, ScEcR-A is produced at amplification but is absent just prior. We discuss these results in relation to the model of ecdysone regulation of DNA amplification.
We thank Beth Ryder for her initial work on developmental expression of Sciara EcR. Grant funding from National Institutes of Health to SAG (GM35929) is gratefully acknowledged. GML was supported by a student fellowship from the Agency for Science, Technology and Research (A*STAR), Singapore.
The experiments in this manuscript comply with current laws in the USA.
Conflict of interest
The authors declare that they have no conflict of interest.
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