USP16 is a deubiquitinase that removes monoubiquitin from histone H2A at lysine 120, reversing a repressive epigenetic mark and acting as a transcriptional coactivator 1. This deubiquitination is essential for histone H3 phosphorylation and chromosome 21 during mitosis. USP16 also deubiquitinates non-histone substrates, including ribosomal protein RPS27A to promote 40S ribosomal maturation, and tektin proteins to enhance their stability. Beyond nucleosomal substrates, recent structural studies reveal USP16 recognizes H2AK119Ub nucleosomes through a mechanism distinct from the multi-subunit PR-DUB complex 1, and translocates to mitochondria where it influences mitochondrial integrity and respiratory function alongside PRC1 2. In disease contexts, USP16 dysregulation contributes to hepatocellular carcinoma through ZEB2 deubiquitination and TGF-β signaling 3, and genetic reduction of USP16 rescues neural precursor cell dysfunction and cognitive defects in Alzheimer's disease models by regulating senescence genes and BMP signaling 4. USP16 expression is transcriptionally regulated by NFκB signaling 5. Recent evidence indicates USP16 may be a therapeutic target, though cancer cells can develop compensatory mechanisms to escape USP16 inhibition 6.