Human estrogen receptor introduced into the Xenopus oocyte represses expression from an artificial frog estrogen response element

C. S. Watson

    Research output: Contribution to journalArticle

    4 Citations (Scopus)

    Abstract

    Although the estrogen responsiveness and estrogen receptors of Xenopus hepatocytes have been well described, oocytes of this species have not previously been shown to contain estrogen receptors (ER). Recombinant human ER (HER) was expressed in oocytes in a dose dependent fashion as measured by [35S]methionine incorporation into newly synthesized proteins. Chloramphenicol acetyl transferase (CAT) reporter plasmids, driven by a herpes simplex thymidine kinase promotor with or without a 17 base pair estrogen response element (ERE) from the vitellogenin A2 gene, were also injected into oocytes. When injected without the accompanying HER sequences, the construct containing the ERE expressed 10-fold more CAT activity, and this response was saturable as demonstrated by injecting increasing amounts of reporter plasmid. These results suggest either the activity of small amounts of a Xenopus ER (measured here by LH-20 assay), or the presence of some endogenous oocyte protein other than the ER that can interact with this ERE. When HER was co-expressed with ERECAT, CAT expression was suppressed over a wide range of HER concentrations. This unexpected repression may be due to displacement of an estrogen receptor or other endogenous oocyte regulatory protein on the ERE. HER's positive regulatory activity may require transcription factors that are lacking or insufficient in the oocyte. Alternatively the simple 17 base pair ERE may not provide DNA binding sites for such transcription factors.

    Original languageEnglish (US)
    Pages (from-to)423-431
    Number of pages9
    JournalJournal of Steroid Biochemistry and Molecular Biology
    Volume38
    Issue number4
    DOIs
    StatePublished - 1991

    Fingerprint

    Response Elements
    Xenopus
    Estrogen Receptors
    Anura
    Oocytes
    Estrogens
    Chloramphenicol
    Transferases
    Base Pairing
    Plasmids
    Transcription Factors
    Vitellogenins
    Herpes Simplex
    Proteins
    Thymidine Kinase
    varespladib methyl
    Methionine
    Hepatocytes
    Assays
    Genes

    ASJC Scopus subject areas

    • Biochemistry
    • Endocrinology

    Cite this

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    title = "Human estrogen receptor introduced into the Xenopus oocyte represses expression from an artificial frog estrogen response element",
    abstract = "Although the estrogen responsiveness and estrogen receptors of Xenopus hepatocytes have been well described, oocytes of this species have not previously been shown to contain estrogen receptors (ER). Recombinant human ER (HER) was expressed in oocytes in a dose dependent fashion as measured by [35S]methionine incorporation into newly synthesized proteins. Chloramphenicol acetyl transferase (CAT) reporter plasmids, driven by a herpes simplex thymidine kinase promotor with or without a 17 base pair estrogen response element (ERE) from the vitellogenin A2 gene, were also injected into oocytes. When injected without the accompanying HER sequences, the construct containing the ERE expressed 10-fold more CAT activity, and this response was saturable as demonstrated by injecting increasing amounts of reporter plasmid. These results suggest either the activity of small amounts of a Xenopus ER (measured here by LH-20 assay), or the presence of some endogenous oocyte protein other than the ER that can interact with this ERE. When HER was co-expressed with ERECAT, CAT expression was suppressed over a wide range of HER concentrations. This unexpected repression may be due to displacement of an estrogen receptor or other endogenous oocyte regulatory protein on the ERE. HER's positive regulatory activity may require transcription factors that are lacking or insufficient in the oocyte. Alternatively the simple 17 base pair ERE may not provide DNA binding sites for such transcription factors.",
    author = "Watson, {C. S.}",
    year = "1991",
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    AB - Although the estrogen responsiveness and estrogen receptors of Xenopus hepatocytes have been well described, oocytes of this species have not previously been shown to contain estrogen receptors (ER). Recombinant human ER (HER) was expressed in oocytes in a dose dependent fashion as measured by [35S]methionine incorporation into newly synthesized proteins. Chloramphenicol acetyl transferase (CAT) reporter plasmids, driven by a herpes simplex thymidine kinase promotor with or without a 17 base pair estrogen response element (ERE) from the vitellogenin A2 gene, were also injected into oocytes. When injected without the accompanying HER sequences, the construct containing the ERE expressed 10-fold more CAT activity, and this response was saturable as demonstrated by injecting increasing amounts of reporter plasmid. These results suggest either the activity of small amounts of a Xenopus ER (measured here by LH-20 assay), or the presence of some endogenous oocyte protein other than the ER that can interact with this ERE. When HER was co-expressed with ERECAT, CAT expression was suppressed over a wide range of HER concentrations. This unexpected repression may be due to displacement of an estrogen receptor or other endogenous oocyte regulatory protein on the ERE. HER's positive regulatory activity may require transcription factors that are lacking or insufficient in the oocyte. Alternatively the simple 17 base pair ERE may not provide DNA binding sites for such transcription factors.

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