Poly(dA:dT), a ubiquitous promoter element that stimulates transcription via its intrinsic DNA structure.
Many yeast promoters contain homopolymeric dA:dT sequences that affect nucleosome formation in vitro and are required for wild-type levels of transcription in vivo. Here, we show that poly(dA:dT) is a novel promoter element whose function depends on its intrinsic structure, not its interaction with sequence-specific, DNA-binding proteins. First, poly(dA:dT) stimulates Gcn4-activated transcription in a manner that is length dependent and inversely related to intracellular Gcn4 levels. Second, Datin, the only known poly(dA:dT)-binding protein, behaves as a repressor through poly(dA:dT) sequences. Third, poly(dG:dC), a structurally dissimilar homopolymer that also affects nucleosomes, has transcriptional properties virtually identical to those of poly(dA:dT). Three probes of chromatin structure including HinfI endonuclease cleavage in vivo indicate that poly(dA:dT) increases accessibility of the Gcn4 binding site and adjacent sequences in physiological chromatin. These observations suggest that, by virtue of its intrinsic structure, poly(dA:dT) locally affects nucleosomes and increases the accessibility of transcription factors bound to nearby sequences.
Iyer
V
V
Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA.
Struhl
K
K
D001483:Base Sequence; D001665:Binding Sites; D004271:DNA, Fungal / Q000737:chemistry / Q000235:genetics; D004268:DNA-Binding Proteins / Q000378:metabolism; D050483:Dopamine Plasma Membrane Transport Proteins; D005656:Fungal Proteins / Q000378:metabolism; D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins; D008969:Molecular Sequence Data; D015394:Molecular Structure; D009419:Nerve Tissue Proteins; D009707:Nucleosomes / Q000378:metabolism; D011067:Poly dA-dT / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D011089:Polydeoxyribonucleotides / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011401:Promoter Regions, Genetic; D011494:Protein Kinases / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins; D014158:Transcription, Genetic
C060858:DAT1 protein, S cerevisiae; D004271:DNA, Fungal; D004268:DNA-Binding Proteins; D050483:Dopamine Plasma Membrane Transport Proteins; D005656:Fungal Proteins; D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins; D009419:Nerve Tissue Proteins; D009707:Nucleosomes; D011089:Polydeoxyribonucleotides; D029701:Saccharomyces cerevisiae Proteins; D011067:Poly dA-dT; C019530:poly(dC-dG); D011494:Protein Kinases