CUL4A also knonw as Cullin 4A is the ubiquitin ligase component of a multimeric complex involved in the degradation of DNA damage-response proteins. CUL4A plays a crucial role in the ubiquitin-proteasome system, specifically in the selective degradation of proteins, which is vital for maintaining cellular homeostasis and regulating various biological processes, including cell cycle and DNA repair. CUL4A functions as part of an E3 ubiquitin ligase complex, where CUL4A associates with Nedd-8, a ubiquitin-like protein, to facilitate ubiquitination of target substrates. This post-translational modification is essential for controlling protein levels and activity within cells, thereby influencing processes such as cell proliferation and response to stress.