title: Quantitative phosphoproteomics reveals new roles for the protein phosphatase PP6 in mitotic cells.
abstract: Protein phosphorylation is an important regulatory mechanism controlling mitotic progression. Protein phosphatase 6 (PP6) is an essential enzyme with conserved roles in chromosome segregation and spindle assembly from yeast to humans. We applied a baculovirus-mediated gene silencing approach to deplete HeLa cells of the catalytic subunit of PP6 (PP6c) and analyzed changes in the phosphoproteome and proteome in mitotic cells by quantitative mass spectrometry-based proteomics. We identified 408 phosphopeptides on 272 proteins that increased and 298 phosphopeptides on 220 proteins that decreased in phosphorylation upon PP6c depletion in mitotic cells. Motif analysis of the phosphorylated sites combined with bioinformatics pathway analysis revealed previously unknown PP6c-dependent regulatory pathways. Biochemical assays demonstrated that PP6c opposed casein kinase 2-dependent phosphorylation of the condensin I subunit NCAP-G, and cellular analysis showed that depletion of PP6c resulted in defects in chromosome condensation and segregation in anaphase, consistent with dysregulation of condensin I function in the absence of PP6 activity.
authors.affiliation: Department of Biochemistry, Geisel School of Medicine at Dartmouth, Hanover, NH 03755, USA.
authors.forename: Scott F
authors.initials: SF
authors.lastname: Rusin
authors.affiliation: Norris Cotton Cancer Center, Geisel School of Medicine at Dartmouth, Lebanon, NH 03756, USA.
authors.forename: Kate A
authors.initials: KA
authors.lastname: Schlosser
authors.affiliation: Norris Cotton Cancer Center, Geisel School of Medicine at Dartmouth, Lebanon, NH 03756, USA.
authors.forename: Mark E
authors.initials: ME
authors.lastname: Adamo
authors.affiliation: Department of Biochemistry, Geisel School of Medicine at Dartmouth, Hanover, NH 03755, USA. Norris Cotton Cancer Center, Geisel School of Medicine at Dartmouth, Lebanon, NH 03756, USA. arminja.n.kettenbach@dartmouth.edu.
authors.forename: Arminja N
authors.initials: AN
authors.lastname: Kettenbach
mesh_terms: D000595:Amino Acid Sequence; D064096:Aurora Kinase A / Q000378:metabolism; D001665:Binding Sites / Q000235:genetics; D015153:Blotting, Western; D047390:Casein Kinase II / Q000378:metabolism; D059447:Cell Cycle Checkpoints / Q000235:genetics; D018797:Cell Cycle Proteins / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D013058:Mass Spectrometry / Q000379:methods; D008938:Mitosis / Q000235:genetics; D010748:Phosphopeptides / Q000378:metabolism; D010749:Phosphoprotein Phosphatases / Q000235:genetics / Q000378:metabolism*; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation; D020543:Proteome / Q000378:metabolism*; D040901:Proteomics / Q000379:methods*; D034622:RNA Interference; D015398:Signal Transduction
chemical_list: D018797:Cell Cycle Proteins; C533611:NCAPG protein, human; D010748:Phosphopeptides; D010750:Phosphoproteins; D020543:Proteome; D064096:Aurora Kinase A; D047390:Casein Kinase II; D010749:Phosphoprotein Phosphatases; C106079:protein phosphatase 6