Proteasome-mediated degradation of transcriptional activators correlates with activation domain potency in vivo.
We show that the intracellular concentration of transcriptional activator proteins is regulated by the proteasome-mediated protein degradation pathway. The rate of degradation of activators by proteasomes correlates with activation domain potency in vivo. Mutations either in the activation domain residues involved in target protein interaction or in the DNA-binding domain residues essential for DNA binding abolish the transcriptional activation function in vivo and render the activator resistant to degradation by proteasomes. Finally, using a rapamycin-regulated gene expression system, we show that recruiting activation domains to DNA-bound receptor proteins greatly enhanced the rate of degradation of reconstituted activators. These observations suggest that in mammalian cells efficient recruitment of activator-target protein complexes to the promoter means that they are subjected to rapid degradation by proteasomes. We propose that proteasome-mediated control of the intracellular levels of transcriptional activators could play an important role in the regulation of gene expression.
Molinari
E
E
ARIAD Gene Therapeutics Inc., 26 Landsdowne Street, Cambridge, MA 02139, USA.
Gilman
M
M
Natesan
S
S
D000952:Antigens, Polyomavirus Transforming / Q000235:genetics; D001665:Binding Sites; D003546:Cysteine Endopeptidases / Q000378:metabolism*; D004268:DNA-Binding Proteins; D005354:Fibrosarcoma; D005656:Fungal Proteins / Q000235:genetics; D005786:Gene Expression Regulation; D019267:Hemagglutinin Glycoproteins, Influenza Virus / Q000235:genetics; D006801:Humans; D007700:Kinetics; D009097:Multienzyme Complexes / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics; D015533:Transcriptional Activation; D014162:Transfection; D014407:Tumor Cells, Cultured
D000952:Antigens, Polyomavirus Transforming; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; C052130:GAL4 protein, S cerevisiae; D019267:Hemagglutinin Glycoproteins, Influenza Virus; D009097:Multienzyme Complexes; D011993:Recombinant Fusion Proteins; D029701:Saccharomyces cerevisiae Proteins; D015534:Trans-Activators; D014157:Transcription Factors; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex