a, Yeast two-hybrid assays in which PP1dis2+ and PP1sds21+ sequences were fused to the activating domain of Gal4 and the indicated version of the core homology domains of the PP2A regulatory subunits B56par1+ (encoding amino acids 112–424) and B56par2+ (encoding amino acids 213–525) were fused to the Gal4 DNA-binding domain according to the procedures of the matchmaker gold yeast two-hybrid system. b, Blotting the cell extracts with 12CA5 and 9E10 monoclonal antibodies that recognized HA and Myc epitopes within the cassettes harbouring the activation (HA) and DNA-binding domains (Myc) indicated that equivalent protein expression levels were achieved for each version of the protein. Probing for the DNA replication factor Ctf4 was used as a loading control41. Thus, the failure of the PP1-docking-site mutants to interact with PP1dis2+ suggests that the change in the PP1-docking site abolished the affinity between the two molecules. Biological replicates: for a, n = 3; for b, n = 1.