USP21 (Ubiquitin Specific Peptidase 21) is a Protein Coding gene. Diseases associated with USP21 include Neurodevelopmental Disorder With Spasticity And Poor Growth. Among its related pathways are TNF signaling (REACTOME) and Integrated Breast Cancer Pathway. Gene Ontology (GO) annotations related to this gene include transcription coactivator activity and cysteine-type peptidase activity. An important paralog of this gene is USP2. Deubiquitinates histone H2A, a specific tag for epigenetic transcriptional repression, thereby acting as a coactivator. Deubiquitination of histone H2A releaves the repression of di- and trimethylation of histone H3 at 'Lys-4', resulting in regulation of transcriptional initiation. Regulates gene expression via histone H2A deubiquitination. Also capable of removing NEDD8 from NEDD8 conjugates but has no effect on Sentrin-1 conjugates. Deubiquitinates BAZ2A/TIP5 leading to its stabilization.