The pRb-related protein p130 is regulated by phosphorylation-dependent proteolysis via the protein-ubiquitin ligase SCF(Skp2).
p130 is a tumor suppressor of the pocket protein family whose expression is posttranscriptionally regulated and largely G0 restricted. The mechanism of down-regulation of p130 expression in proliferating cells was investigated. Our results indicate that the decline of p130 expression as G0 cells reenter the cell cycle is due to a decrease in protein stability. The enhancement of p130 turnover in late G1 and S phase compared with G0 and early G1 phase was dependent on Cdk4/6-specific phosphorylation of p130 on Serine 672, and independent of Cdk2 activity. The activity of the ubiquitin ligase complex Skp1-Cul1/Cdc53-F-box protein Skp2 (SCF(Skp2)) and the proteasome were necessary for p130 degradation. In vitro, recombinant Skp2 was able to bind hyperphosphorylated but not dephosphorylated p130. Furthermore, in vitro polyubiquitination of p130 by SCF(Skp2) was specifically dependent on phosphorylation of p130 on Serine 672. Thus, like the Cdk inhibitor p27(Kip1), p130 turnover is regulated by Cdk-dependent G1 phosphorylation leading to ubiquitin-dependent proteolysis.
Tedesco
Donato
D
Department of Molecular Biology, MB-7, The Scripps Research Institute, La Jolla, California 92037, USA.
Lukas
Jiri
J
Reed
Steven I
SI
D048868:Adaptor Proteins, Signal Transducing; D042846:CDC2-CDC28 Kinases; D002453:Cell Cycle / Q000502:physiology; D018797:Cell Cycle Proteins; D002478:Cells, Cultured; D051357:Cyclin-Dependent Kinase 2; D051358:Cyclin-Dependent Kinase 4; D051361:Cyclin-Dependent Kinase 6; D018844:Cyclin-Dependent Kinases / Q000378:metabolism; D003546:Cysteine Endopeptidases / Q000378:metabolism; D005656:Fungal Proteins / Q000378:metabolism; D006801:Humans; D008025:Ligases / Q000235:genetics / Q000378:metabolism*; D009097:Multienzyme Complexes / Q000378:metabolism; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D046988:Proteasome Endopeptidase Complex; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011506:Proteins; D011518:Proto-Oncogene Proteins; D050717:Retinoblastoma-Like Protein p130; D029701:Saccharomyces cerevisiae Proteins; D012694:Serine / Q000378:metabolism; D025801:Ubiquitin / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases
D048868:Adaptor Proteins, Signal Transducing; C081185:CKS1 protein, S cerevisiae; D018797:Cell Cycle Proteins; D005656:Fungal Proteins; D009097:Multienzyme Complexes; D010750:Phosphoproteins; D011506:Proteins; D011518:Proto-Oncogene Proteins; C493837:RBL2 protein, human; D050717:Retinoblastoma-Like Protein p130; D029701:Saccharomyces cerevisiae Proteins; D025801:Ubiquitin; D012694:Serine; D044767:Ubiquitin-Protein Ligases; D017346:Protein Serine-Threonine Kinases; D042846:CDC2-CDC28 Kinases; C495894:CDK2 protein, human; C495900:CDK4 protein, human; C495911:CDK6 protein, human; D051357:Cyclin-Dependent Kinase 2; D051358:Cyclin-Dependent Kinase 4; D051361:Cyclin-Dependent Kinase 6; D018844:Cyclin-Dependent Kinases; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex; D008025:Ligases