Sequence Elements in Both Subunits of the DNA Fragmentation Factor Are Essential for Its Nuclear Transport

DNA cleavage is a biochemical hallmark of apoptosis. In humans, apoptotic DNA cleavage is executed by DNA fragmentation factor (DFF) 40. In proliferating cells DFF40 is expressed in the presence of its chaperone and inhibitor DFF45, which results in the formation of the DFF complex. Here, we present...

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Bibliographic Details
Published in:The Journal of biological chemistry 2007-12, Vol.282 (49), p.35821-35830
Main Authors: Neimanis, Sonja, Albig, Werner, Doenecke, Detlef, Kahle, Joerg
Format: Article
Language:English
Subjects:
Active Transport, Cell Nucleus - physiology
alpha Karyopherins - metabolism
Apoptosis - physiology
Apoptosis Regulatory Proteins - metabolism
beta Karyopherins - metabolism
Cell Nucleus - metabolism
Cytoplasm - metabolism
Deoxyribonucleases - metabolism
HeLa Cells
Humans
Models, Biological
Multiprotein Complexes - metabolism
Nuclear Localization Signals - metabolism
Poly-ADP-Ribose Binding Proteins
Protein Binding - physiology
Protein Structure, Tertiary - physiology
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Summary:DNA cleavage is a biochemical hallmark of apoptosis. In humans, apoptotic DNA cleavage is executed by DNA fragmentation factor (DFF) 40. In proliferating cells DFF40 is expressed in the presence of its chaperone and inhibitor DFF45, which results in the formation of the DFF complex. Here, we present a systematic analysis of the nuclear import of the DFF complex. Our in vitro experiments demonstrate that the importin α/β-heterodimer mediates the translocation of the DFF complex from the cytoplasm to the nucleus. Both DFF subunits interact directly with the importin α/β-heterodimer. However, importin α/β binds more tightly to the DFF complex compared with the individual subunits. Additionally, the isolated C-terminal regions of both DFF subunits together bind importin α/β more strongly than the individual C termini. Our results from in vivo studies reveal that the C-terminal regions of both DFF subunits harbor nuclear localization signals. Furthermore, nuclear import of the DFF complex requires the C-terminal regions of both subunits. In more detail, one basic cluster in the C-terminal region of each subunit, DFF40 (RLKRK) and DFF45 (KRAR), is essential for nuclear accumulation of the DFF complex. Based on these findings two alternative models for the interaction of importin α/β with the DFF complex are presented.
ISSN:0021-9258
1083-351X
DOI:10.1074/jbc.M703110200