Repo-Man (white) brings PP1γ onto chromatin at anaphase.
By countering kinase activities, protein phosphatase 1 (PP1) regulates many different cellular signaling pathways. PP1 comes in three flavors whose specificities rely mainly on their precise targeting. Trinkle-Mulcahy and colleagues sought to identify the proteins responsible for this targeting.
The authors began by looking for different localization patterns for the α and γ PP1 isoforms. PP1γ, they found, jumped onto chromosomes at anaphase. PP1α, on the other hand, was mainly excluded from mitotic chromatin.
This sharp difference allowed the group to find the protein that recruited PP1 to chromatin. Proteins that associated with PP1γ, but not PP1α, were identified by feeding cell lines that expressed either GFP, PP1α-GFP, or PP1γ-GFP with three different isotopes of arginine. They then isolated all...
