Direct Interaction of Arabidopsis SGO1 with PP2A B′ Subunits Revealed by Microscale Thermophoresis

Accurate chromosome segregation during meiosis requires protection of centromeric cohesion mediated by shugoshin (SGO) proteins and Protein Phosphatase 2A (PP2A). In Arabidopsis thaliana, genetic and cytological studies have demonstrated that PP2A B′ regulatory subunits are essential for maintaining centromeric cohesion; however, direct biochemical evidence for their interaction with SGO1 in plants is lacking. Here, we used microscale thermophoresis (MST) to investigate and quantify the binding between fluorescently labeled GST-SGO1 and the PP2A B′α and B′β subunits. SGO1 exhibited concentration-dependent binding to both subunits, with dissociation constants (Kd) of 5.49 ± 0.88 µM for B′α and 1.89 ± 0.38 µM for B′β, indicating an approximately threefold higher affinity for B′β. These results provide direct quantitative biochemical evidence for a specific interaction between Arabidopsis SGO1 and PP2A B′ subunits.