Determinants of the nucleolar targeting of protein phosphatase-1

AbstractThe ubiquitously expressed protein Ser/Thr phosphatase-1 isoforms PP1α, PP1β and PP1γ1 are dynamically targeted to distinct, but overlapping cellular compartments by associated proteins. Within the nucleus of HeLa cells, EGFP-tagged PP1γ1 and PP1β were predominantly targeted to the nucleoli, while PP1α showed a more diffuse distribution. Using PP1 chimaeras and point mutants we show here that a single N-terminal residue, i.e., Gln20 for PP1α, Arg19 for PP1β and Arg20 for PP1γ1 accounts for their distinct subnuclear distribution. Our data also suggest that the N-terminus of PP1β and PP1γ1 harbours an interaction site for one or more nucleolar interactors