Otubain 1, also known as OTUB1, is a member of the OUT (ovarian tumor) superfamily of predicted cysteine proteases and inhibits cytokine gene transcription in the immune system via its interaction with a ubiquitin protease and E3 ubiquitin ligase. This protein is a highly specific ubiquitin iso-peptidase, and cleaves ubiquitin from branched poly-ubiquitin chains but not from ubiquitinated substrate