Abstract 1740: Characterization of CDK9 role in the DNA damage response

Abstract

Abstract Introduction: The DNA damage response (DDR) is a well-coordinated pathway capable of sensing and repairing different types of DNA damage. Double-strand break (DSB) lesions activate the ATM-CHK2 axis, which is responsible for the cell cycle arrest, prompting cells for DNA repair. DSBs are primarily repaired through two distinct pathways: homology-directed recombination (HR) and non-homologous end-joining (NHEJ). BRCA1 and 53BP1 play an important role in DDR by orchestrating the decision between HR and NHEJ, but the precise mechanisms regarding both pathways are not entirely understood. Previously, our group identified the putative interaction of the cyclin-dependent kinase 9 (CDK9) with BRCA1 and BARD1 (BRCA1-associated RING domain 1). CDK9 is a component of the positive transcription elongation complex and has been implicated in genome integrity maintenance associated with the replication stress response. More recently, we characterized CDK9 as a DDR player by modulating BRCA1 recruitment to DNA damaged sites and consequently the HR pathway. We also showed that cells lacking CDK9 failure to form RAD51, but not 53BP1, ionizing radiation-induced foci (IRIF) and are characterized by an increased sensitivity to DSBs Methods and Results: Here we show that the CDK9-BRCA1 interaction occurs through BRCA1 N-terminal region in a BRCA1-BARD1 heterodimer formation-dependent manner. We also identified a CDK9 mutant (E369A) that abrogates the CDK9-BRCA1 interaction (through BRCA1 C-terminal region). Moreover, we characterized CHK2 as a novel CDK9-interaction partner, through ectopic GST-pulldown and constitutive co-immunoprecipitation assays. Further, cells lacking CDK9 are deficient in promoting G2/M arrest after IR-induced DNA damage. We also identified new CDK9 interactions in a DDR-related context using a TAP-MS approach. Conclusion: Collectively, our data suggest a role for CDK9 in the DDR through DNA damage repair and cell cycle checkpoint regulation Citation Format: Thales C. Nepomuceno, Guilherme Suarez-Kurtz, Alvaro N. Monteiro, Marcelo A. Carvalho. Characterization of CDK9 role in the DNA damage response [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1740.