CUL4B also known as Cullin 4B is a member of the cullin family. CUL4 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. CUL4 functions as part of an E3 ubiquitin ligase complex, where CUL4 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. CUL4′s regulation of protein degradation underscores its importance in cellular signaling pathways and potential implications in cancer and other diseases where these pathways are disrupted.