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Mol Endocrinol. 2003 Jul;17(7):1315-31. Epub 2003 Mar 27.

Specific ubiquitin-conjugating enzymes promote degradation of specific nuclear receptor coactivators.

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Department of Surgery, Medical Microbiology & Immunology and Cancer Center Criss II, Creighton University, Omaha, Nebraska 68178, USA.


Nuclear receptor coactivators (NRCoAs) are nuclear hormone receptor-associated regulatory proteins that interact with members of the nuclear receptor superfamily in the presence of their cognate ligand, enhancing their transcriptional activity. The identification of ubiquitin-proteasome pathway proteins as coactivators provides evidence that ubiquitin-proteasome-mediated protein degradation plays an integral role in eukaryotic gene transcription. It has also been observed that nuclear receptors themselves are ubiquitinated and degraded in a hormone-dependent manner and that ubiquitin-proteasome function is essential for most nuclear receptors to function as transactivators. Here, we show that specific ubiquitin-proteasome pathway enzymes target specific NRCoA proteins in vivo and in vitro. First, using a temperature-sensitive cell line that contains a thermolabile ubiquitin-activating E1 enzyme, we confirmed that NRCoA proteins are targets of the ubiquitin-proteasome pathway. Then using coimmunoprecipitation studies, we also demonstrate that in vivo, NRCoA proteins are ubiquitinated. Finally, we illustrate that in vitro, NRCoA ubiquitination and degradation depend on the ubiquitin-activating enzyme (E1) and on specific ubiquitin-conjugating enzymes (E2) for each of the coactivators.

[Indexed for MEDLINE]

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