RelB is the key component of the alternative NF-κB (nuclear factor κB) signalling pathway. However, RelB exerts also a negative effect via the recruitment of a DNMT1 (DNA methyltransferase 1)–Daxx (death domain-associated protein) complex to NF-κB target genes. Importantly, the molecular mechanisms which determine the functions of RelB are still largely unknown. In the present study, we aimed to analyse whether ubiquitination of RelB might be involved in the regulation of RelB. Indeed, RelB is constitutively polyubiquitinated in the B-cell lines Namalwa and 70Z/3. Although a PMA+ionomycin-induced augmentation of RelB polyubiquitination was linked to its proteasomal degradation in B-cells, the constitutive RelB polyubiquitination seems to affect non-proteasomal functions. Consistently, a significant RelB polyubiquitination in HEK (human embryonic kidney)-293 cells correlated with an augmentation of the transcriptional activity of RelB. Yet, neither nuclear localization nor DNA binding was enhanced by RelB polyubiquitination. Interestingly, basal RelB polyubiquitination depends neither on Lys48 nor on Lys63 conjugates, but might involve unconventional ubiquitin conjugates. Mapping of the ubiquitination target sites in RelB revealed the existence of various lysine residues, which serve as ubiquitination acceptors. However, only the substitution of Lys273/274 and Lys305/308 significantly decreased the basal RelB activity and the ubiquitin-induced augmentation of the RelB activity. Collectively, these results imply a dual role of RelB polyubiquitination for the stability and activity of this transcription factor.
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Research Article|
October 28 2008
Identification of lysine residues critical for the transcriptional activity and polyubiquitination of the NF-κB family member RelB
Julia Leidner;
Julia Leidner
*Institute of Physiological Chemistry, Ulm University, Albert-Einstein-Allee 11, 89081 Ulm, Germany
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Lysann Palkowitsch;
Lysann Palkowitsch
*Institute of Physiological Chemistry, Ulm University, Albert-Einstein-Allee 11, 89081 Ulm, Germany
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Uta Marienfeld;
Uta Marienfeld
*Institute of Physiological Chemistry, Ulm University, Albert-Einstein-Allee 11, 89081 Ulm, Germany
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Dietmar Fischer;
Dietmar Fischer
†Institute of Experimental Neurology, Ulm University, Albert-Einstein-Allee 11, 89081 Ulm, Germany
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Ralf Marienfeld
Ralf Marienfeld
1
*Institute of Physiological Chemistry, Ulm University, Albert-Einstein-Allee 11, 89081 Ulm, Germany
1To whom correspondence should be addressed (email ralf.marienfeld@uni-ulm.de).
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Publisher: Portland Press Ltd
Received:
February 22 2008
Revision Received:
July 07 2008
Accepted:
July 11 2008
Accepted Manuscript online:
July 11 2008
Online ISSN: 1470-8728
Print ISSN: 0264-6021
© The Authors Journal compilation © 2008 Biochemical Society
2008
Biochem J (2008) 416 (1): 117–127.
Article history
Received:
February 22 2008
Revision Received:
July 07 2008
Accepted:
July 11 2008
Accepted Manuscript online:
July 11 2008
Citation
Julia Leidner, Lysann Palkowitsch, Uta Marienfeld, Dietmar Fischer, Ralf Marienfeld; Identification of lysine residues critical for the transcriptional activity and polyubiquitination of the NF-κB family member RelB. Biochem J 15 November 2008; 416 (1): 117–127. doi: https://doi.org/10.1042/BJ20080432
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