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Published December 12, 2003 | Published + Supplemental Material
Journal Article Open

A Mammalian Homolog of Drosophila melanogaster Transcriptional Coactivator Intersex Is a Subunit of the Mammalian Mediator Complex

Abstract

The multiprotein Mediator complex is a coactivator required for transcriptional activation of RNA polymerase II transcribed genes by DNA binding transcription factors. We previously partially purified a Med8-containing Mediator complex from rat liver nuclei (Brower, C. S., Sato, S., Tomomori-Sato, C., Kamura, T., Pause, A., Stearman, R., Klausner, R. D., Malik, S., Lane, W. S., Sorokina, I., Roeder, R. G., Conaway, J. W., and Conaway, R. C. (2002) Proc. Natl. Acad. Sci. U. S. A. 99, 10353–10358). Analysis of proteins present in the most highly enriched Mediator fractions by tandem mass spectrometry led to the identification of several new mammalian Mediator subunits, as well as several potential Mediator subunits. Here we identify one of these proteins, encoded by the previously uncharacterized AK000411 open reading frame, as a new subunit of the mammalian Mediator complex. The AK000411 protein, which we designate hIntersex (human Intersex), shares significant sequence similarity with the Drosophila melanogaster intersex protein, which has functional properties expected of a transcriptional coactivator specific for the Drosophila doublesex transactivator. In addition, we show that hIntersex assembles into a subcomplex with Mediator subunits p28b and TRFP. Taken together, our findings identify a new subunit of the mammalian Mediator and shed new light on the architecture of the mammalian Mediator complex.

Additional Information

© 2003 the American Society for Biochemistry and Molecular Biology. Received for publication, October 9, 2003. Originally published In Press as doi:10.1074/jbc.C300444200 on October 22, 2003. Accelerated Publication. We thank W. S. Lane, M. Washburn, and L. Florens for advice on mass spectrometry. We also thank R. G. Roeder and S. Malik for the HeLa cell line stably expressing FLAG-Nut2, M. Carey for the GST-TR construct, and J. Workman for the GST-VP16 construct. This work was supported by National Institutes of Health Grant R37 GM41628. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

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August 22, 2023
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