The SDS22:PP1:I3 complex: SDS22 binding to PP1 loosens the active site metal to prime metal exchange.

SDS22 and Inhibitor-3 (I3) are two ancient regulators of protein phosphatase 1 (PP1) that regulate multiple essential biological processes. Both SDS22 and I3 form stable dimeric complexes with PP1; however, and atypically for PP1 regulators, they also form a triple complex, where both proteins bind to PP1 simultaneously (SPI complex). Here we report the crystal structure of the SPI complex.

Reg1 and Snf1 regulate stress-induced relocalization of protein phosphatase-1 to cytoplasmic granules.

The compartmentalization of cellular function is achieved largely through the existence of membrane-bound organelles. However, recent work suggests a novel mechanism of compartmentalization mediated by membraneless structures that have liquid droplet-like properties and arise through phase separation. Cytoplasmic stress granules (SGs) are the best characterized and are induced by various stressors including arsenite, heat shock, and glucose deprivation.

SDS22 selectively recognizes and traps metal-deficient inactive PP1.

The metalloenzyme protein phosphatase 1 (PP1), which is responsible for ≥50% of all dephosphorylation reactions, is regulated by scores of regulatory proteins, including the highly conserved SDS22 protein. SDS22 has numerous diverse functions, surprisingly acting as both a PP1 inhibitor and as an activator. Here, we integrate cellular, biophysical, and crystallographic studies to address this conundrum.

New ubiquitin-dependent mechanisms regulating the Aurora B-protein phosphatase 1 balance in .

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.

Saccharomyces cerevisiae Mhr1 can bind Xho I-induced mitochondrial DNA double-strand breaks in vivo.

Mitochondrial DNA (mtDNA) double-strand break (DSB) repair is essential for maintaining mtDNA integrity, but little is known about the proteins involved in mtDNA DSB repair. Here, we utilize Saccharomyces cerevisiae as a eukaryotic model to identify proteins involved in mtDNA DSB repair. We show that Mhr1, a protein known to possess homologous DNA pairing activity in vitro, binds to mtDNA DSBs in vivo, indicating its involvement in mtDNA DSB repair.