During my PhD project, I studied the role of several chromatin remodelers in the DNA double strand break (DSB) response. We discovered that both CHD4 and SMARCA5 are required for ubiquitin signaling through the E3 ubiquitin ligases RNF8 and RNF168, which is a central signaling event in the response to DSBs. Furthermore, we found that SMARCA5 actually interacts with RNF168. Both CHD4 and SMARCA5 act at the break site itself and modulate DSB repair. Additionally we found that the DSB repair protein Rad51 is essential for mouse development since Rad51C knock out mice were embryonic lethal. ; Promotor: Leon H.F. Mullenders, Co-promotores: Haico van Attikum, Albert Pastink ; With summary in Dutch ; J.E. Jurriaanse Stichting Sectra.