Interaction between transcriptional activator protein LAC9 and negative regulatory protein GAL80.

Journal Article

In Saccharomyces cerevisiae, transcriptional activation mediated by the GAL4 regulatory protein is repressed in the absence of galactose by the binding of the GAL80 protein, an interaction that requires the carboxy-terminal 28 amino acids of GAL4. The homolog of GAL4 from Kluyveromyces lactis, LAC9, activates transcription in S. cerevisiae and is highly similar to GAL4 in its carboxyl terminus but is not repressed by wild-type levels of GAL80 protein. Here we show that GAL80 does repress LAC9-activated transcription in S. cerevisiae if overproduced. We sought to determine the molecular basis for the difference in the responses of the LAC9 and GAL4 proteins to GAL80. Our results indicate that this difference is due primarily to the fact that under wild-type conditions, the level of LAC9 protein in S. cerevisiae is much higher than that of GAL4, which suggests that LAC9 escapes GAL80-mediated repression by titration of GAL80 protein in vivo. The difference in response to GAL80 is not due to amino acid sequence differences between the LAC9 and GAL4 carboxyl termini. We discuss the implications of these results for the mechanism of galactose metabolism regulation in S. cerevisiae and K. lactis.

Full Text

Duke Authors

Cited Authors

  • Salmeron, JM; Langdon, SD; Johnston, SA

Published Date

  • July 1, 1989

Published In

Volume / Issue

  • 9 / 7

Start / End Page

  • 2950 - 2956

PubMed ID

  • 2550790

International Standard Serial Number (ISSN)

  • 0270-7306

Language

  • eng

Conference Location

  • United States