The Oncogenic Fusion Proteins SET-Nup214 and Sequestosome-1 (SQSTM1)-Nup214 Form Dynamic Nuclear Bodies and Differentially Affect Nuclear Protein and Poly(A)+ RNA Export.
Genetic rearrangements are a hallmark of several forms of leukemia and can lead to oncogenic fusion proteins. One example of an affected chromosomal region is the gene coding for Nup214, a nucleoporin that localizes to the cytoplasmic side of the nuclear pore complex (NPC). We investigated two such fusion proteins, SET-Nup214 and SQSTM1 (sequestosome)-Nup214, both containing C-terminal portions of Nup214. SET-Nup214 nuclear bodies containing the nuclear export receptor CRM1 were observed in the leukemia cell lines LOUCY and MEGAL. Overexpression of SET-Nup214 in HeLa cells leads to the formation of similar nuclear bodies that recruit CRM1, export cargo proteins, and certain nucleoporins and concomitantly affect nuclear protein and poly(A)+RNA export. SQSTM1-Nup214, although mostly cytoplasmic, also forms nuclear bodies and inhibits nuclear protein but not poly(A)+RNA export. The interaction of the fusion proteins with CRM1 is RanGTP-dependent, as shown in co-immunoprecipitation experiments and binding assays. Further analysis revealed that the Nup214 parts mediate the inhibition of nuclear export, whereas the SET or SQSTM1 part determines the localization of the fusion protein and therefore the extent of the effect. SET-Nup214 nuclear bodies are highly mobile structures, which are in equilibrium with the nucleoplasm in interphase and disassemble during mitosis or upon treatment of cells with the CRM1-inhibitor leptomycin B. Strikingly, we found that nucleoporins can be released from nuclear bodies and reintegrated into existing NPC. Our results point to nuclear bodies as a means of preventing the formation of potentially insoluble and harmful protein aggregates that also may serve as storage compartments for nuclear transport factors.
From the Department of Molecular Biology, Faculty of Medicine and the Göttingen Center for Molecular Biosciences (GZMB), Georg August University, Göttingen, Humboldtallee 23, 37073 Göttingen, Germany.
Sarah A
SA
Port
the Institute of Molecular Biology and Medicine, Université Libre de Bruxelles, 6041 Charleroi, Belgium, and.
Adélia
A
Mendes
the Leibniz Institute on Aging,Fritz Lipmann Institute, Beutenbergstrasse 11, 07745 Jena, Germany.
Christina
C
Valkova
From the Department of Molecular Biology, Faculty of Medicine and the Göttingen Center for Molecular Biosciences (GZMB), Georg August University, Göttingen, Humboldtallee 23, 37073 Göttingen, Germany.
Christiane
C
Spillner
the Institute of Molecular Biology and Medicine, Université Libre de Bruxelles, 6041 Charleroi, Belgium, and.
Birthe
B
Fahrenkrog
the Leibniz Institute on Aging,Fritz Lipmann Institute, Beutenbergstrasse 11, 07745 Jena, Germany.
Christoph
C
Kaether
From the Department of Molecular Biology, Faculty of Medicine and the Göttingen Center for Molecular Biosciences (GZMB), Georg August University, Göttingen, Humboldtallee 23, 37073 Göttingen, Germany, rkehlen@gwdg.de.
Ralph H
RH
Kehlenbach
D021581:Active Transport, Cell Nucleus; D004268:DNA-Binding Proteins; D056488:Histone Chaperones / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D045586:Intranuclear Inclusion Bodies / Q000235:genetics / Q000378:metabolism*; D028884:Karyopherins / Q000235:genetics / Q000378:metabolism; D028861:Nuclear Pore Complex Proteins / Q000235:genetics / Q000378:metabolism*; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D011061:Poly A / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism*; D018160:Receptors, Cytoplasmic and Nuclear / Q000235:genetics / Q000378:metabolism; D000071456:Sequestosome-1 Protein / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D000097606:Exportin 1 Protein
D004268:DNA-Binding Proteins; D056488:Histone Chaperones; D028884:Karyopherins; D028861:Nuclear Pore Complex Proteins; D009687:Nuclear Proteins; D011061:Poly A; D012333:RNA, Messenger; D018160:Receptors, Cytoplasmic and Nuclear; D000071456:Sequestosome-1 Protein; D014157:Transcription Factors; D000097606:Exportin 1 Protein; C085914:NUP214 protein, human; C513473:SET protein, human; C099718:SQSTM1 protein, human
CRM1; Nup214; SET; leukemia; mRNA; nuclear pore; nuclear transport; nucleus; p62 (sequestosome-1 (SQSTM1))