Ubiquitin Signals Proteolysis-Independent Stripping of Transcription Factors

Ubiquitination of transcription activators has been reported to regulate transcription via both proteolytic and nonproteolytic routes, yet the function of the ubiquitin (Ub) signal in the nonproteolytic process is poorly understood. By use of the heterologous transcription activator LexA-VP16 in Saccharomyces cerevisiae, we show that monoubiquitin fusion of the activator prevents stable interactions between the activator and DNA, leading to transcription inhibition without activator degradation. We identify the AAA+ ATPase Cdc48 and its cofactors as the Ub receptor responsible for extracting the monoubiquitinated activator from DNA. Our results suggest that deubiquitination of the activator is critical for transcription activation. These findings with LexA-VP16 extend in both yeast and mammalian cells to native transcription activators Met4 and R-Smads, respectively, that are known to be oligo-ubiquitinated. The results illustrate a role for Ub and Cdc48 in transcriptional regulation and gene expression that is independent of proteolysis. [Display omitted] •Cdc48 extracts Ub-LexA-VP16 from DNA independently of proteasomal degradation•Ub-LexA-VP16 deubiquitination efficiency correlates with transcriptional activity•Monoubiquitin fused to LexA-VP16 is sufficient to recruit Cdc48•Cdc48/p97 regulates promoter occupancy by Met4 in yeast and R-Smads in mammals Regulation of eukaryotic transcription often entails ubiquitin modification of transcription activators. Ndoja et al. show that attachment of a single ubiquitin to an activator can inhibit transcription nonproteolytically by recruiting Cdc48/p97 to remove activators from DNA, thereby maintaining a repressed state until transcription is triggered by deubiquitination of the activator.