Assembly of the 26S proteasome is regulated by phosphorylation of the p45/Rpt6 ATPase subunit.
We investigated whether the assembly/disassembly of the 26S proteasome is regulated by phosphorylation/dephosphorylation. The regulatory complex disassembled from the 26S proteasome was capable of phosphorylating the p45/Sug1/Rpt6 subunit, suggesting that the protein kinase is activated upon dissociation of the 26S proteasome or that the phosphorylation site of p45 becomes susceptible to the protein kinase. In addition, the p45-phosphorylated regulatory complex was found to be incorporated into the 26S proteasome. When the 26S proteasome was treated with alkaline phosphatase, it was dissociated into the 20S proteasome and the regulatory complex. Furthermore, the p45 subunit and the C3/alpha2 subunit were cross-linked with DTBP, whereas these subunits were not cross-linked by dephosphorylating the 26S proteasome. These results indicate that the 26S proteasome is disassembled into the constituent subcomplexes by dephosphorylation and that it is assembled by phosphorylation of p45 by a protein kinase, which is tightly associated with the regulatory complex. It was also revealed that the p45 subunit is directly associated with the 20S proteasome alpha-subunit C3 in a phosphorylation-dependent manner.
Satoh
K
K
Department of Biochemistry, Graduate School of Pharmaceutical Sciences, Hokkaido University, Sapporo 060-0812, Japan.
Sasajima
H
H
Nyoumura
K I
KI
Yokosawa
H
H
Sawada
H
H
D000074183:ATPases Associated with Diverse Cellular Activities; D048868:Adaptor Proteins, Signal Transducing; D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000378:metabolism; D000345:Affinity Labels / Q000378:metabolism; D000818:Animals; D015153:Blotting, Western; D002352:Carrier Proteins / Q000378:metabolism*; D003432:Cross-Linking Reagents / Q000378:metabolism; D003546:Cysteine Endopeptidases / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D007096:Imidoesters / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins; D060588:LIM Domain Proteins; D009097:Multienzyme Complexes / Q000378:metabolism; D010447:Peptide Hydrolases / Q000378:metabolism*; D010766:Phosphorylation; D046988:Proteasome Endopeptidase Complex; D011494:Protein Kinases / Q000378:metabolism*; D013552:Swine; D014157:Transcription Factors
D048868:Adaptor Proteins, Signal Transducing; D000345:Affinity Labels; D002352:Carrier Proteins; D003432:Cross-Linking Reagents; D007096:Imidoesters; D047908:Intracellular Signaling Peptides and Proteins; D060588:LIM Domain Proteins; D009097:Multienzyme Complexes; C092282:PSMC5 protein, human; C106843:SUG1 protein, mammalian; D014157:Transcription Factors; C007471:dimethyl dithiobispropionimidate; D000255:Adenosine Triphosphate; D011494:Protein Kinases; D010447:Peptide Hydrolases; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex; C061553:ATP dependent 26S protease; D000251:Adenosine Triphosphatases; D000074183:ATPases Associated with Diverse Cellular Activities