Cullin3-KLHL15 ubiquitin ligase mediates CtIP protein turnover to fine-tune DNA-end resection

  • Nat Commun. 2016 Aug 26;7:12628. doi: 10.1038/ncomms12628.
Lorenza P Ferretti  1 ,  Sarah-Felicitas Himmels  1 ,  Anika Trenner  1 ,  Christina Walker  1 ,  Christine von Aesch  1 ,  Aline Eggenschwiler  1 ,  Olga Murina  1 ,  Radoslav I Enchev  2 ,  Matthias Peter  2 ,  Raimundo Freire  3 ,  Antonio Porro  1 ,  Alessandro A Sartori  1
Affiliations
  • 1. University of Zurich, Institute of Molecular Cancer Research, Winterthurerstrasse 190, 8057 Zurich, Switzerland.
  • 2. ETH Zurich, Institute of Biochemistry, Department of Biology, Otto-Stern-Weg 3, 8093 Zurich, Switzerland.
  • 3. Unidad de Investigación, Hospital Universitario de Canarias, Instituto de Tecnologías Biomédicas, Ofra s/n, La Cuesta, La Laguna, Tenerife, Spain.
PMID: 27561354 DOI: 10.1038/ncomms12628
Abstract

Human CtIP is a decisive factor in DNA double-strand break repair pathway choice by enabling DNA-end resection, the first step that differentiates homologous recombination (HR) from non-homologous end-joining (NHEJ). To coordinate appropriate and timely execution of DNA-end resection, CtIP function is tightly controlled by multiple protein-protein interactions and post-translational modifications. Here, we identify the Cullin3 E3 Ligase substrate adaptor Kelch-like protein 15 (KLHL15) as a new interaction partner of CtIP and show that KLHL15 promotes CtIP protein turnover via the ubiquitin-proteasome pathway. A tripeptide motif (FRY) conserved across vertebrate CtIP proteins is essential for KLHL15-binding; its mutation blocks KLHL15-dependent CtIP ubiquitination and degradation. Consequently, DNA-end resection is strongly attenuated in cells overexpressing KLHL15 but amplified in cells either expressing a CtIP-FRY mutant or lacking KLHL15, thus impacting the balance between HR and NHEJ. Collectively, our findings underline the key importance and high complexity of CtIP modulation for genome integrity.