New ubiquitin-dependent mechanisms regulating the Aurora B–protein phosphatase 1 balance in Saccharomyces cerevisiae

Abstract

Protein ubiquitylation regulates many cellular processes, including cell division. We report here a novel mutation altering the E1 ubiquitin-activating enzyme () that suppresses the temperature sensitivity and chromosome loss phenotype of a well-characterized Aurora B mutant (). The mutation increases histone H3-S10 phosphorylation in the strain, indicating that acts by increasing Ipl1 activity and/or reducing the opposing protein phosphatase 1 (PP1; Glc7 in) phosphatase activity. Consistent with this hypothesis, Ipl1 protein levels and stability are elevated in the mutant, likely mediated via the E2 enzymes Ubc4 and Cdc34. In contrast, the mutation does not affect Glc7 stability, but exhibits synthetic lethality with several mutations. Moreover, cells have an altered subcellular distribution of Glc7 and form nuclear Glc7 foci. These effects are likely mediated via the E2 enzymes Rad6 and Cdc34. Our new allele reveals new roles for ubiquitylation in regulating the Ipl1-Glc7 balance in budding yeast. While ubiquitylation likely regulates Ipl1 protein stability via the canonical proteasomal degradation pathway, a non-canonical ubiquitin-dependent pathway maintains normal Glc7 localization and activity.This article has an associated First Person interview with the first author of the paper.

SDS22 selectively recognizes and traps metal-deficient inactive PP1

“…All buffers, proteins, DNA, and yeast strains (SI Appendix, Tables S4 and S5) are described in the SI Appendix (36,(45)(46)(47). SPR experiments performed using a 4-channel Reichert 4SPR instrument fitted with autosampler and degassing pump (SI Appendix).…”