A Gal4-sigma 54 hybrid protein that functions as a potent activator of RNA polymerase II transcription in yeast.
The bacterial final sigma(54) protein associates with core RNA polymerase to form a holoenzyme complex that renders cognate promoters enhancer-dependent. Although unusual in bacteria, enhancer-dependent transcription is the paradigm in eukaryotes. Here we report that a fragment of Escherichia coli final sigma(54) encompassing amino acid residues 29-177 functions as a potent transcriptional activator in yeast when fused to a Gal4 DNA binding domain. Activation by Gal4-final sigma(54) is TATA-dependent and requires the SAGA coactivator complex, suggesting that Gal4-final sigma(54) functions by a normal mechanism of transcriptional activation. Surprisingly, deletion of the AHC1 gene, which encodes a polypeptide unique to the ADA coactivator complex, stimulates Gal4-final sigma(54)-mediated activation and enhances the toxicity of Gal4-final sigma(54). Accordingly, the SAGA and ADA complexes, both of which include Gcn5 as their histone acetyltransferase subunit, exert opposite effects on transcriptional activation by Gal4-final sigma(54). Gal4-final sigma(54) activation and toxicity are also dependent upon specific final sigma(54) residues that are required for activator-responsive promoter melting by final sigma(54) in bacteria, implying that activation is a consequence of final sigma(54)-specific features rather than a structurally fortuitous polypeptide fragment. As such, Gal4-final sigma(54) represents a novel tool with the potential to provide insight into the mechanism by which natural activators function in eukaryotic cells.
Chen
B S
BS
Department of Biochemistry, Division of Nucleic Acids Enzymology, Robert Wood Johnson Medical School, Piscataway, New Jersey 08854-5635, USA.
Sun
Z W
ZW
Hampsey
M
M
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics / Q000502:physiology; D002868:Chromosomal Proteins, Non-Histone; D004268:DNA-Binding Proteins; D012321:DNA-Directed RNA Polymerases / Q000235:genetics / Q000502:physiology*; D029968:Escherichia coli Proteins; D005656:Fungal Proteins / Q000235:genetics / Q000502:physiology*; D017353:Gene Deletion; D051548:Histone Acetyltransferases; D046911:Macromolecular Substances; D008969:Molecular Sequence Data; D009154:Mutation; D011494:Protein Kinases / Q000235:genetics; D012319:RNA Polymerase II / Q000378:metabolism*; D051877:RNA Polymerase Sigma 54; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins; D012808:Sigma Factor / Q000235:genetics / Q000502:physiology*; D015534:Trans-Activators / Q000502:physiology; D014157:Transcription Factors / Q000235:genetics / Q000502:physiology*; D015533:Transcriptional Activation; D000099224:p300-CBP-Associated Factor
D001426:Bacterial Proteins; D002868:Chromosomal Proteins, Non-Histone; D004268:DNA-Binding Proteins; D012321:DNA-Directed RNA Polymerases; D029968:Escherichia coli Proteins; D005656:Fungal Proteins; D051548:Histone Acetyltransferases; D046911:Macromolecular Substances; D011494:Protein Kinases; D012319:RNA Polymerase II; D051877:RNA Polymerase Sigma 54; D011993:Recombinant Fusion Proteins; D029701:Saccharomyces cerevisiae Proteins; D012808:Sigma Factor; D015534:Trans-Activators; D014157:Transcription Factors; C090575:ADA2 protein, S cerevisiae; C403402:AHC1 protein, S cerevisiae; C052130:GAL4 protein, S cerevisiae; C070633:Gal-VP16; C083323:NGG1 protein, S cerevisiae; C497751:rpoN protein, E coli; C501392:GCN5 protein, S cerevisiae; D000099224:p300-CBP-Associated Factor