Mediates ubiquitination and susbsequent desumoylation/degradation of sumoylated proteins and proteins containing SUMO-like domains. Promotes UBC4-dependent ubiquitination that mediates the proteolytic down-regulation of sumoylated proteins. Involved in the stimulation of ubiquitin conjugating enzymes, including UBC1, UBC4, UBC5 and UBC13-MMS2. Acts as a critical suppressor of gross chromosomal rearrangements (GCRs) during normal cell cycle progression. Has a role in localizing the DNA damage protein DCD2. Involved in stabilizing, restarting or resolving transiently stalled replication forks. Prevents accumulation of DNA damage during cell cycle progression. Along with SIR2, promotes silencing of genes at telomeric or ribosomal DNA (rDNA) loci.