Polyubiquitin genes UBC and UBB mainly contribute to Ub content in basal conditions.
UBC is the most responsive gene to differently induced proteotoxic stress.
Ub ribosomal fusion genes are not involved in the proteotoxic stress response.
UV-induced genotoxic stress acts post-transcriptionally by stabilizing Ub mRNAs.
Multiple transcription start sites were identified within the UBC promoter.