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A Single GAL4 Dimer Can Maximally Activate Transcription Under Physiological Conditions
H. Eric Xu, Thomas Kodadek and Stephen Albert Johnston
Proceedings of the National Academy of Sciences of the United States of America
Vol. 92, No. 17 (Aug. 15, 1995), pp. 7677-7680
Published by: National Academy of Sciences
Stable URL: http://www.jstor.org/stable/2368111
Page Count: 4
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Most eukaryotic promoters contain multiple binding sites for one or more transcriptional activators that interact in a synergistic manner. A common view is that synergism is a manifestation of the need for many contacts between activators and the general transcription machinery that a single activator presumably cannot fulfill. In this model, various combinations of protein-protein interactions control the level of gene expression. However, we show here that under physiological conditions, a single binding site and presumably binding of a single dimer of the prototypical yeast activator GAL4 can activate transcription to the maximum possible level in vivo. Synergistic effects in this natural system are shown to be consistent with cooperative DNA binding. These results point to DNA occupancy as the major element in fine tuning gene expression in the galactose regulon.
Proceedings of the National Academy of Sciences of the United States of America © 1995 National Academy of Sciences