title: Polo-like kinase interacts with proteasomes and regulates their activity.
abstract: The polo-like kinase (Plk) has been shown to be associated with the anaphase-promoting complex at the transition from metaphase to anaphase and to regulate ubiquitination, the process that targets proteins for degradation by proteasomes. In this study, we have identified proteasomal proteins interacting with Plk by mass spectrometry and found that Plk and 20S proteasome subunits could be reversibly immunoprecipitated from both human CA46 cells and HEK 293 cells transfected with HA-Plk. Furthermore, both coprecipitated Plk and baculovirus-expressed Plk were able to phosphorylate proteasome subunits, and metabolic labeling studies indicate that Plk is partially responsible for the phosphorylation of 20S proteasome subunits C9 and C8 in vivo. In addition, phosphorylation of proteasomes by Plk enhanced proteolytic activity toward an artificial substrate Suc-L-L-V-Y-AMC in vitro and in vivo. Finally, we were also able to detect Plk associated with 26S proteasomes under certain conditions. Together our results suggest that Plk is an important mitotic regulator of proteasome activity.
authors.affiliation: Biological Mechanisms Section, Laboratory of Leukocyte Biology, National Cancer Institute-Frederick Cancer Research and Development Center, Maryland 21702, USA.
authors.forename: Y
authors.initials: Y
authors.lastname: Feng
authors.forename: D L
authors.initials: DL
authors.lastname: Longo
authors.forename: D K
authors.initials: DK
authors.lastname: Ferris
mesh_terms: D000705:Anaphase; D000818:Animals; D016367:Baculoviridae / Q000378:metabolism; D002460:Cell Line; D003546:Cysteine Endopeptidases / Q000378:metabolism*; D029721:Drosophila Proteins; D015180:Electrophoresis, Gel, Two-Dimensional; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D007074:Immunoglobulin G / Q000378:metabolism; D007313:Insecta; D013058:Mass Spectrometry; D008677:Metaphase; D008938:Mitosis; D009097:Multienzyme Complexes / Q000378:metabolism*; D019319:Okadaic Acid / Q000494:pharmacology; D010766:Phosphorylation; D011233:Precipitin Tests; D046988:Proteasome Endopeptidase Complex; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D014162:Transfection; D014407:Tumor Cells, Cultured
chemical_list: D029721:Drosophila Proteins; D007074:Immunoglobulin G; D009097:Multienzyme Complexes; D011994:Recombinant Proteins; D019319:Okadaic Acid; D017346:Protein Serine-Threonine Kinases; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex