Involved in both DNA replication and cell cycle control. Unprocessed SDE2 interacts with PCNA via its PIP-box. The interaction with PCNA prevents monoubiquitination of the latter thereby inhibiting translesion DNA synthesis. The binding of SDE2 to PCNA also leads to processing of SDE2 by an unidentified deubiquitinating enzyme, cleaving off the N-terminal ubiquitin-like domain. The resulting mature SDE2 is degraded by the DCX(DTL) complex in a cell cycle- and DNA damage dependent manner. Binding of SDE2 to PCNA is necessary to counteract damage due to ultraviolet light induced replication stress. The complete degradation of SDE2 is necessary to allow S-phase progression. The PIP-box (PCNA interacting peptide) motif mediates both the interaction with PCNA and cleavage of the SDE2 precursor by a deubiquitinating enzyme. The SAP domain is necessary for specific binding to DNA. The propeptide displays a ubiquitin-like fold. The protein is cleaved at Gly-71 by a deubiquitinating enzyme to form the active SDE2. Belongs to the SDE2 family. Extended N-terminus.