The yeast SWI-SNF complex facilitates binding of a transcriptional activator to nucleosomal sites in vivo.
The Saccharomyces cerevisiae SWI-SNF complex is a 2-MDa protein assembly that is required for the function of many transcriptional activators. Here we describe experiments on the role of the SWI-SNF complex in activation of transcription by the yeast activator GAL4. We find that while SWI-SNF activity is not required for the GAL4 activator to bind to and activate transcription from nucleosome-free binding sites, the complex is required for GAL4 to bind to and function at low-affinity, nucleosomal binding sites in vivo. This SWI-SNF dependence can be overcome by (i) replacing the low-affinity sites with higher-affinity, consensus GAL4 binding sequences or (ii) placing the low-affinity sites into a nucleosome-free region. These results define the criteria for the SWI-SNF dependence of gene expression and provide the first in vivo evidence that the SWI-SNF complex can regulate gene expression by modulating the DNA binding of an upstream activator protein.
Burns
L G
LG
Department of Biochemistry and Molecular Biology, University of Massachusetts Medical Center, Worcester 01605, USA.
Peterson
C L
CL
D000251:Adenosine Triphosphatases; D001665:Binding Sites; D002868:Chromosomal Proteins, Non-Histone; D018983:DNA Footprinting; D004271:DNA, Fungal / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D005656:Fungal Proteins / Q000378:metabolism*; D005690:Galactose / Q000378:metabolism; D015966:Gene Expression Regulation, Fungal / Q000502:physiology; D005800:Genes, Fungal / Q000235:genetics; D009687:Nuclear Proteins; D009707:Nucleosomes / Q000378:metabolism*; D011401:Promoter Regions, Genetic / Q000235:genetics; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins; D015534:Trans-Activators / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D015533:Transcriptional Activation / Q000502:physiology
D002868:Chromosomal Proteins, Non-Histone; D004271:DNA, Fungal; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; C052130:GAL4 protein, S cerevisiae; D009687:Nuclear Proteins; D009707:Nucleosomes; C078562:SWI1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D015534:Trans-Activators; D014157:Transcription Factors; D000251:Adenosine Triphosphatases; C499333:SNF2 protein, S cerevisiae; D005690:Galactose