Nuclear and subnuclear targeting sequences of the protein phosphatase-1 regulator NIPP1.
NIPP1 is a nuclear subunit of protein phosphatase-1 (PP1) that colocalizes with pre-mRNA splicing factors in speckles. We report here that the nuclear and subnuclear targeting of NIPP1, when expressed in HeLa cells or COS-1 cells as a fusion protein with the enhanced-green-fluorescent protein (EGFP), are mediated by distinct sequences. While NIPP1-EGFP can cross the nuclear membrane passively, the active transport to the nucleus is mediated by two independent nuclear localization signals in the central domain of NIPP1, which partially overlap with binding site(s) for PP1. Furthermore, the concentration of NIPP1-EGFP in the nuclear speckles requires the 'ForkHead-Associated' domain in the N terminus. This domain is also required for the nuclear retention of NIPP1 when active transport is blocked. Our data imply that the nuclear and subnuclear targeting of NIPP1 are controlled independently.
Jagiello
I
I
Afdeling Biochemie, Faculteit Geneeskunde, Katholieke Universiteit Leuven, B-3000 Leuven, Belgium.
Van Eynde
A
A
Vulsteke
V
V
Beullens
M
M
Boudrez
A
A
Keppens
S
S
Stalmans
W
W
Bollen
M
M
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002352:Carrier Proteins; D002460:Cell Line; D004722:Endoribonucleases; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D008969:Molecular Sequence Data; D019913:Nuclear Localization Signals; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1; D021381:Protein Transport; D016601:RNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D013347:Subcellular Fractions / Q000378:metabolism*
D002352:Carrier Proteins; D047908:Intracellular Signaling Peptides and Proteins; D019913:Nuclear Localization Signals; D016601:RNA-Binding Proteins; C021042:protein phosphatase inhibitor-1; D004722:Endoribonucleases; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1; C097081:PPP1R8 protein, human