Ubp8 and SAGA Regulate Snf1 AMP Kinase Activity

Abstract

Posttranslational modifications of histone proteins play important roles in the modulation of gene expression. The Saccharomyces cerevisiae (yeast) 2-MDa SAGA (Spt-Ada-Gcn5) complex, a well-studied multisubunit histone modifier, regulates gene expression through Gcn5-mediated histone acetylation and Ubp8-mediated histone deubiquitination. Using a proteomics approach, we determined that the SAGA complex also deubiquitinates nonhistone proteins, including Snf1, an AMP-activated kinase. Ubp8-mediated deubiquitination of Snf1 affects the stability and phosphorylation state of Snf1, thereby affecting Snf1 kinase activity. Others have reported that Gal83 is phosphorylated by Snf1, and we found that deletion of UBP8 causes decreased phosphorylation of Gal83, which is consistent with the effects of Ubp8 loss on Snf1 kinase functions. Overall, our data indicate that SAGA modulates the posttranslational modifications of Snf1 in order to fine-tune gene expression levels.

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ACKNOWLEDGMENTS

We thank William Dubinsky (The University of Texas Dental Branch) for performing the mass spectrometry experiments. We thank Ambro van Hoof, Daneen Grossman, Kevin Morano, and Hugo Tapia (The University of Texas Health Science Center at Houston), Hugo Bellen and Nikos Giagtzoglou (Baylor College of Medicine), and Jerry Workman and Kenneth Lee (Stowers Institute) for yeast strains, reagents, and equipment that were used to conduct this work. We also thank Daniel Finley (Harvard Medical School) and Richard Gardner (University of Washington) for generously sharing plasmids. We thank Ambro van Hoof, John Latham, Yi Chun Chen, Jill Butler, Boyko Atanassov, and Marek Napierela (The University of Texas M. D. Anderson Cancer Center) for fruitful discussions.

This work was supported by the National Institute of Child Health and Human Development Training Grant in “Differentiation and Development” to M.A.W. (2 T32 HD07325) and grants from the NIH (R01GM51189) and the MDACC Senior Research Trust to S.Y.R.D.