WDR21A, also known as DCAF4 (DDB1 and CUL4 associated factor 4), is a WD repeat-containing protein that functions as a substrate receptor for the CUL4-DDB1 E3 ubiquitin-protein ligase complex, playing a crucial role in the ubiquitination and subsequent regulation of specific target proteins within the cell. Characterized by its WD40 repeat domain which facilitates protein-protein interactions, WDR21A is involved in critical biological processes such as cell population proliferation and post-translational protein modification. Structural studies have revealed that WDR21A interacts with the DDB1 adaptor protein via a distinct H-box motif, and multiple alternatively spliced transcript variants have been identified for this gene, underscoring its regulatory complexity.