Clastosome: a subtype of nuclear body enriched in 19S and 20S proteasomes, ubiquitin, and protein substrates of proteasome.
Nuclear bodies represent a heterogeneous class of nuclear structures. Herein, we describe that a subset of nuclear bodies is highly enriched in components of the ubiquitin-proteasome pathway of proteolysis. We coined the term clastosome (from the Greek klastos, broken and soma, body) to refer to this type of nuclear body. Clastosomes contain a high concentration of 1) ubiquitin conjugates, 2) the proteolytically active 20S core and the 19S regulatory complexes of the 26S proteasome, and 3) protein substrates of the proteasome. Although detected in a variety of cell types, clastosomes are scarce under normal conditions; however, they become more abundant when proteasomal activity is stimulated. In contrast, clastosomes disappear when cells are treated with proteasome inhibitors. Protein substrates of the proteasome that are found concentrated in clastosomes include the short-lived transcription factors c-Fos and c-Jun, adenovirus E1A proteins, and the PML protein. We propose that clastosomes are sites where proteolysis of a variety of protein substrates is taking place.
Department of Anatomy and Cell Biology, Faculty of Medicine, University of Cantabria, 39011 Santander, Spain.
Miguel
M
Lafarga
Maria Teresa
MT
Berciano
Emma
E
Pena
Isabel
I
Mayo
Jose G
JG
Castaño
Dirk
D
Bohmann
João Pedro
JP
Rodrigues
João Paulo
JP
Tavanez
Maria
M
Carmo-Fonseca
D000818:Animals; D000831:Animals, Newborn; D022003:Cell Nucleus Structures / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D002478:Cells, Cultured; D003546:Cysteine Endopeptidases / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000378:metabolism; D005260:Female; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D009097:Multienzyme Complexes / Q000037:antagonists & inhibitors / Q000378:metabolism*; D009363:Neoplasm Proteins / Q000378:metabolism; D009687:Nuclear Proteins / Q000378:metabolism*; D000071156:Promyelocytic Leukemia Protein; D046988:Proteasome Endopeptidase Complex; D021122:Protein Subunits / Q000378:metabolism*; D016760:Proto-Oncogene Proteins c-fos / Q000235:genetics / Q000378:metabolism; D016755:Proto-Oncogene Proteins c-jun / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D012583:Schwann Cells / Q000166:cytology / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism; D025521:Tumor Suppressor Proteins; D025801:Ubiquitin / Q000378:metabolism*
D004791:Enzyme Inhibitors; D009097:Multienzyme Complexes; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D000071156:Promyelocytic Leukemia Protein; D021122:Protein Subunits; D016760:Proto-Oncogene Proteins c-fos; D016755:Proto-Oncogene Proteins c-jun; D014157:Transcription Factors; D025521:Tumor Suppressor Proteins; D025801:Ubiquitin; C070576:PML protein, human; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex