Aurora B kinase (Ipl1 in S. cerevisiae) is part of the chromosomal passenger complex that is central for chromosomal attachment to the spindle during mitosis and for cytokinesis. An important counterforce is protein phosphatase 1 (PP1, Glc7 in S.cerevisiae), which dephosphorylates Aurora B target substrates, in addition to having many other roles. PP1, as well as Aurora B, needs to be tightly controlled during mitosis for accurate chromosome segregation. Protein ubiquitylation is an abundant protein modification that regulates protein stability and degradation. Ubiquitylation of Aurora B is known to control its localization, but components of the ubiquitin pathway that modify Aurora B activity await characterization. In their Research Article, Kelly Tatchell and colleagues (Ravindran et al., 2018) report a missense mutation in the E1 ubiquitin-activating enzyme UBA1 that suppresses an Ipl1 mutation in yeast. Chromosome loss is reversed, and the phosphorylation of histone H3 at residue S10 is increased in the ipl1 uba1 double mutant. Furthermore, the authors find elevated Ipl1 levels and increased stability of the protein in the uba1 mutant. The stability of Glc7 is not affected in these conditions, but the authors show an altered subcellular distribution and nuclear foci of Glc7. In summary, this new Uba1 allele highlights an ubiquitin-dependent regulation of the Ipl1–Glc7 balance in yeast.