{
  "abstract": "Humans and other vertebrates contain two estrogen receptors (ERs), ER-alpha and ER-beta, which mediate the physiological actions of three estrogens: estrone (E1), estradiol (E2) and estriol (E3). Of these three estrogens, in vivo, E2 is the strongest transcriptional activator of ER-alpha and ER-beta, E1 is next most active, followed by E3. We studied transcriptional activation of human ER-alpha and ER-beta by E2, E1 and E3 in African green monkey kidney (COS-7) cells, which we compared with studies of estrogen stimulation of ER transcription in human em-bryonic kidney (HEK-293) cells. To our surprise, in COS-7 cells, E3 had the lowest half-maximal response (EC50) for human ER-alpha and ER-beta than either E2, which was second most active estrogen, or E1. In contrast, for human ER-alpha and ER-beta transfected into HEK-293 cells, E2 was the most active estrogen, followed by E1 and E3. Similar results were found in COS-7 cells and HEK-293 cells transfected with elephant shark ER-alpha and ER-beta. Thus, under some conditions, E3 is a more active estrogen than either E2 or E1. This suggests that E3 may be a novel physiological ligand for the ER in some mammalian cells, including the placenta, where E3 levels increase substantially during pregnancy.",
  "abstract_shown": true,
  "affiliations": [
    "Hokkaido University"
  ],
  "article_type": "New results",
  "arxiv": null,
  "author_total": 4,
  "authors": [
    {
      "name": "Y. Ao"
    },
    {
      "name": "R. M. d. R. Cabizares"
    },
    {
      "name": "M. E. Baker"
    },
    {
      "affs": [
        0
      ],
      "name": "Y. Katsu"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/1gn786wxksbdh.bib",
  "cited_by": 0,
  "doi": "10.64898/2026.07.03.736429",
  "fulltext_url": "https://www.biorxiv.org/content/10.64898/2026.07.03.736429v2.full",
  "id": "1gn786wxksbdh",
  "issns": [],
  "landing_url": "https://www.biorxiv.org/content/10.64898/2026.07.03.736429v2",
  "language": null,
  "licence": "CC-BY-ND",
  "licence_label": "CC BY-ND",
  "licence_source": "article",
  "licence_url": "https://creativecommons.org/licenses/by-nd/4.0/",
  "metadata_licence": null,
  "native_subjects": [
    [
      "biorxiv",
      "evolutionary biology"
    ]
  ],
  "openalex": null,
  "pdf_url": "https://www.biorxiv.org/content/10.64898/2026.07.03.736429v2.full.pdf",
  "pmcid": null,
  "pmid": null,
  "published": "2026-07-03",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/1gn786wxksbdh.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:20:56Z",
      "native_id": "10.64898/2026.07.03.736429",
      "source": "biorxiv",
      "url": "https://www.biorxiv.org/content/10.64898/2026.07.03.736429v2"
    }
  ],
  "subjects": [
    {
      "field": "biology",
      "origin": "biorxiv:evolutionary biology",
      "subfield": "evolutionary-biology"
    }
  ],
  "title": "Estriol is a Stronger Transcriptional Activator than is either 17beta-Estradiol or Estrone of Hu-man and Elephant Shark Estrogen Receptor-alpha and Estrogen Receptor-beta transfected into COS-7 Cells",
  "title_text": "Estriol is a Stronger Transcriptional Activator than is either 17beta-Estradiol or Estrone of Hu-man and Elephant Shark Estrogen Receptor-alpha and Estrogen Receptor-beta transfected into COS-7 Cells",
  "type": "preprint",
  "updated_at": "2026-10-30T12:20:56Z",
  "url": "https://research.draconitic.com/paper/1gn786wxksbdh",
  "venue": "bioRxiv",
  "versions": [
    {
      "doi": "10.1016/j.jsbmb.2026.107122",
      "pid": null,
      "relation": "published-as",
      "title": null,
      "venue": null
    }
  ]
}