TOM1p, a yeast hect-domain protein which mediates transcriptional regulation through the ADA/SAGA coactivator complexes.

The hect-domain has been characterized as a conserved feature of a group of E3 ubiquitin ligases. Here we show that the yeast hect-domain protein TOM1p regulates transcriptional activation through effects on the ADA transcriptional coactivator proteins. Null mutations of tom1 result in similar defects in transcription from ADH2 and HIS3 ...
promoters, and enhanced transcription from the GAL10 promoter as do null mutations in ngg1/ada3. Strains with disruptions of both ngg1 and tom1 have the same phenotype as strains with a disruption of only ngg1 implying that these genes are acting through the same pathway. In the absence of TOM1p, the normal associations of the ADA proteins with SPT3p and the TATA-binding protein are reduced. The action of TOM1p is most likely mediated through ubiquitination since mutation of Cys3235 to Ala, corresponding residues of which are required for thioester bond formation with ubiquitin in other hect-domain proteins, results in similar changes in transcription as the null mutation. A direct role for TOM1p in regulation of ADA-associated proteins is further supported by the finding that SPT7p is ubiquitinated in a TOM1p-dependent fashion and that TOM1p coimmunoprecipitates with the ADA proteins.
Mesh Terms:
Acetyltransferases, Alcohol Dehydrogenase, Cysteine, DNA-Binding Proteins, Endopeptidases, Fungal Proteins, Gene Expression Regulation, Fungal, Histone Acetyltransferases, Homeodomain Proteins, Hydro-Lyases, Mutation, Precipitin Tests, Promoter Regions, Genetic, Recombinant Proteins, Repressor Proteins, Saccharomyces cerevisiae Proteins, TATA-Box Binding Protein, Transcription Factors, Transcriptional Activation, Ubiquitin-Protein Ligases, Yeasts
J. Mol. Biol.
Date: Oct. 09, 1998
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