Oncogenic exon 2 mutations in Mediator subunit MED12 disrupt allosteric activation of cyclin C-CDK8/19

Min Ju Park, Hailian Shen, Jason M. Spaeth, Jaana H. Tolvanen, Courtney Failor, Jennifer F. Knudtson, Jessica McLaughlin, Sunil Krishna Halder, Qiwei Yang, Serdar E. Bulun, Ayman Al-Hendy, Robert S. Schenken, Lauri A. Aaltonen, Thomas G. Boyer

Research output: Contribution to journalArticle

12 Scopus citations

Abstract

Somatic mutations in exon 2 of the RNA polymerase II transcriptional Mediator subunit MED12 occur at high frequency in uterine fibroids (UFs) and breast fibroepithelial tumors as well as recurrently, albeit less frequently, in malignant uterine leimyosarcomas, chronic lymphocytic leukemias, and colorectal cancers. Previously, we reported that UF-linked mutations in MED12 disrupt its ability to activate cyclin C (CycC)- dependent kinase 8 (CDK8) in Mediator, implicating impaired Mediator-associated CDK8 activity in the molecular pathogenesis of these clinically significant lesions. Notably, the CDK8 paralog CDK19 is also expressed in myometrium, and both CDK8 and CDK19 assemble into Mediator in a mutually exclusive manner, suggesting that CDK19 activity may also be germane to the pathogenesis of MED12 mutation-induced UFs. However, whether and how UF-linked mutations in MED12 affect CDK19 activation is unknown. Herein, we show that MED12 allosteri-cally activates CDK19 and that UF-linked exon 2 mutations in MED12 disrupt its CDK19 stimulatory activity. Furthermore, we find that within the Mediator kinase module, MED13 directly binds to the MED12 C terminus, thereby suppressing an apparent UF mutation-induced conformational change in MED12 that otherwise disrupts its association with CycC-CDK8/19. Thus, in the presence of MED13, mutant MED12 can bind, but cannot activate, CycC-CDK8/19. These findings indicate that MED12 binding is necessary but not sufficient for CycC-CDK8/19 activation and reveal an additional step in the MED12-dependent activation process, one critically dependent on MED12 residues altered by UF-linked exon 2 mutations. These findings confirm that UF-linked mutations in MED12 disrupt composite Mediator-associated kinase activity and identify CDK8/19 as prospective therapeutic targets in UFs.

Original languageEnglish (US)
Pages (from-to)4870-4882
Number of pages13
JournalJournal of Biological Chemistry
Volume293
Issue number13
DOIs
Publication statusPublished - Jan 1 2018

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ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

Cite this

Park, M. J., Shen, H., Spaeth, J. M., Tolvanen, J. H., Failor, C., Knudtson, J. F., ... Boyer, T. G. (2018). Oncogenic exon 2 mutations in Mediator subunit MED12 disrupt allosteric activation of cyclin C-CDK8/19. Journal of Biological Chemistry, 293(13), 4870-4882. https://doi.org/10.1074/jbc.RA118.001725