DNA looping induced by a transcriptional enhancer in vivo.
Enhancers are DNA sequences that can activate gene transcription from remote positions. In yeast, regulatory sequences that are functionally equivalent to the metazoan enhancers are called upstream activating sequences (UASs). UASs show a lower degree of flexibility than their metazoan counterparts, but can nevertheless activate transcription from a distance of >1000 bp from the promoter. One of several models for the mechanism of action of transcriptional enhancers proposes that enhancer-bound activating proteins contact promoter-bound transcription factors and thereby get in close proximity to the promoter region with concomitant looping of the intervening DNA. We tested the mode of enhancer activity in yeast. A polymerase II-transcribed gene was paired with a remote, inducible enhancer. An independent reporter system was inserted next to the promoter to monitor the potential modes of enhancer activity. Our results show that the enhancer activated the reporter system only in the presence of a functional promoter. We also demonstrate that the heterologous expression of GAGA, a factor known to facilitate DNA loop formation, allows enhancer action in yeast over a distance of 3000 bp.
Petrascheck
Michael
M
Institute of Molecular Biology, University of Zurich Winterthurerstrasse 190, CH-8057 Zurich, Switzerland. mpetrasc@fhcrc.org
Escher
Dominik
D
Mahmoudi
Tokameh
T
Verrijzer
C Peter
CP
Schaffner
Walter
W
Barberis
Alcide
A
D000818:Animals; D004247:DNA / Q000737:chemistry*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D029721:Drosophila Proteins / Q000378:metabolism*; D004742:Enhancer Elements, Genetic; D017930:Genes, Reporter; D009690:Nucleic Acid Conformation; D011401:Promoter Regions, Genetic; D012319:RNA Polymerase II / Q000235:genetics / Q000378:metabolism; D012320:RNA Polymerase III / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics; D015534:Trans-Activators / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism*; D015533:Transcriptional Activation
D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D015534:Trans-Activators; D014157:Transcription Factors; C063460:Trl protein, Drosophila; D004247:DNA; D012319:RNA Polymerase II; D012320:RNA Polymerase III