USP21(redirected from USP23)
USP21A gene on chromosome 1q22 that encodes an enzyme which specifically deubiquitinates histone H2A (but not H2B), a specific tag for epigenetic transcriptional repression, thereby acting as a coactivator. Deubiquitination of histone H2A relieves the repression of di- and trimethylation of histone H3 at Lys-4, is a prerequisite for subsequent phosphorylation of histone H3 and upregulation of transcription, and is required for chromosome segregation when cells enter into mitosis. USP21 also removes NEDD8 from NEDD8 conjugates. It is highly expressed in the heart, pancreas and in skeletal muscle. USP21 is also a less preferred gene symbol for what is now designated as USP25, see there.
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