Probable ubiquitin ligase protein involved in many cellular processes, such as transcription regulation, maintenance of nuclear structure, cell cycle, mRNA export and rRNA maturation. E3 ubiquitin ligase proteins mediate ubiquitination and subsequent proteasomal degradation of target proteins. Involved in transcription regulation by interacting, and probably mediating, ubiquitination of some subunit of the SAGA complex. Required for SPT7 ubiquitination. Participates in mRNA export from the nucleus by regulating the transport of hnRNP proteins. Required for the shuttling of hnRNP protein NAB2, probably by mediating ubiquitination of a protein associated with NAB2. Also required for full induction of the general stress and heat-shock responses. Involved in 18S rRNA maturation by affecting several early steps in the rRNA processing pathway. S-ubiquitinyl-[E2 ubiquitin-conjugating enzyme]-L-cysteine + [acceptor protein]-L-lysine = [E2 ubiquitin-conjugating enzyme]-L-cysteine + N(6)-ubiquitinyl-[acceptor protein]-L-lysine. Protein modification; protein ubiquitination. Interacts with the ADA3/NGG1 subunit of the SAGA complex. Interacts with KRR1. Present with 350 molecules/cell in log phase SD medium. Belongs to the UPL family. TOM1/PTR1 subfamily.