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DNA‐binding properties of the ecdysteroid receptor‐complex (EcR/USP) of the epithelial cell line from Chironomus tentans
Author(s) -
Elke Carsten,
Rauch Peter,
SpindlerBarth Margarethe,
Spindler KlausDieter
Publication year - 1999
Publication title -
archives of insect biochemistry and physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.576
H-Index - 66
eISSN - 1520-6327
pISSN - 0739-4462
DOI - 10.1002/(sici)1520-6327(1999)41:3<124::aid-arch3>3.0.co;2-c
Subject(s) - receptor , biology , ecdysteroid , hormone , dna , steroid hormone , microbiology and biotechnology , medicine , endocrinology , biochemistry
DNA‐binding features of EcR and USP were investigated using a 0.4 M NaCl extract of the epithelial cell line of Chironomus tentans by means of electrophoretic mobility shift assays (EMSAs). It is shown that the DNA‐binding is enhanced by hormone administration and that in the hormone dependent shift, both EcR and USP, are present. Furthermore, we demonstrate that under these conditions, EcR/USP form a unique complex on inverted repeat elements (PAL1 and hsp27‐EcRE), while on direct repeat elements (DR1‐5), a second complex with higher mobility is formed. In this second complex, neither EcR nor USP are present. Thus, an additional difference between PAL1 and DR‐elements is the competition of other factors for DR‐elements, modulating its function as an EcRE. A competition EMSA, using PAL1 as radiolabeled probe, reveals the following order of binding strength: PAL1>DR4/5>DR1>DR2/3/hsp27. Surprisingly, using DR1 as radiolabeled probe, shows a different order of binding strength: DR1>DR2>DR3/4/5/PAL1>hsp27. This indicates that the complexes formed on PAL1 are not identical to the ones formed on DR1 and that both are not easily convertible. Furthermore, the affinity of the EcR/USP complex may be altered under various conditions or by interaction with cofactors. Upon hormone administration, DNA binding of the receptor complex is enhanced, but the difference to hormone‐free binding reactions decreases in course of time, indicating an additional hormone independent activation. Arch. Insect Biochem. Physiol. 41:124–133, 1999. © 1999 Wiley‐Liss, Inc.