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Nucleic Acids Res. 2015 Mar 11;43(5):2575-89. doi: 10.1093/nar/gkv101. Epub 2015 Feb 20.

Ovarian carcinoma CDK12 mutations misregulate expression of DNA repair genes via deficient formation and function of the Cdk12/CycK complex.

Author information

1
Institute of Biomedicine, Biochemistry and Developmental Biology, University of Helsinki, Helsinki FIN-00014, Finland.
2
Central European Institute of Technology (CEITEC), Masaryk University, 62500 Brno, Czech Republic.
3
Institute of Experimental Biology, Faculty of Science, Masaryk University, 61137 Brno, Czech Republic.
4
Center of Advanced European Studies and Research, Group Physical Biochemistry, 53175 Bonn, Germany.
5
Institute of Experimental Biology, Faculty of Science, Masaryk University, 61137 Brno, Czech Republic Institute of Biophysics, Academy of Sciences of the Czech Republic, 61265 Brno, Czech Republic.
6
Central European Institute of Technology (CEITEC), Masaryk University, 62500 Brno, Czech Republic dalibor.blazek@ceitec.muni.cz.
7
Institute of Biomedicine, Biochemistry and Developmental Biology, University of Helsinki, Helsinki FIN-00014, Finland matjaz.barboric@helsinki.fi.

Abstract

The Cdk12/CycK complex promotes expression of a subset of RNA polymerase II genes, including those of the DNA damage response. CDK12 is among only nine genes with recurrent somatic mutations in high-grade serous ovarian carcinoma. However, the influence of these mutations on the Cdk12/CycK complex and their link to cancerogenesis remain ill-defined. Here, we show that most mutations prevent formation of the Cdk12/CycK complex, rendering the kinase inactive. By examining the mutations within the Cdk12/CycK structure, we find that they likely provoke structural rearrangements detrimental to Cdk12 activation. Our mRNA expression analysis of the patient samples containing the CDK12 mutations reveals coordinated downregulation of genes critical to the homologous recombination DNA repair pathway. Moreover, we establish that the Cdk12/CycK complex occupies these genes and promotes phosphorylation of RNA polymerase II at Ser2. Accordingly, we demonstrate that the mutant Cdk12 proteins fail to stimulate the faithful DNA double strand break repair via homologous recombination. Together, we provide the molecular basis of how mutated CDK12 ceases to function in ovarian carcinoma. We propose that CDK12 is a tumor suppressor of which the loss-of-function mutations may elicit defects in multiple DNA repair pathways, leading to genomic instability underlying the genesis of the cancer.

PMID:
25712099
PMCID:
PMC4357706
DOI:
10.1093/nar/gkv101
[Indexed for MEDLINE]
Free PMC Article

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