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Biochim Biophys Acta. 2014 Dec;1844(12):2222-8. doi: 10.1016/j.bbapap.2014.08.013. Epub 2014 Sep 2.

Nuclear proteasomes carry a constitutive posttranslational modification which derails SDS-PAGE (but not CTAB-PAGE).

Author information

1
Centre for Haematology, Division of Experimental Medicine, Faculty of Medicine, Imperial College London, Hammersmith Campus, Commonwealth Building 4th Floor, Du Cane Road, London W12 0NN, United Kingdom.
2
London Research Institute, Clare Hall Laboratories, Blanche Lane, South Mimms, Potters Bar EN6 3LD, United Kingdom.
3
Centre for Haematology, Division of Experimental Medicine, Faculty of Medicine, Imperial College London, Hammersmith Campus, Commonwealth Building 4th Floor, Du Cane Road, London W12 0NN, United Kingdom. Electronic address: m.kleijnen@imperial.ac.uk.

Abstract

We report that subunits of human nuclear proteasomes carry a previously unrecognised, constitutive posttranslational modification. Subunits with this modification are not visualised by SDS-PAGE, which is used in almost all denaturing protein gel electrophoresis. In contrast, CTAB-PAGE readily visualises such modified subunits. Thus, under most experimental conditions, with identical samples, SDS-PAGE yielded gel electrophoresis patterns for subunits of nuclear proteasomes which were misleading and strikingly different from those obtained with CTAB-PAGE. Initial analysis indicates a novel modification of a high negative charge with some similarity to polyADP-ribose, possibly explaining compatibility with (positively-charged) CTAB-PAGE but not (negatively-charged) SDS-PAGE and providing a mechanism for how nuclear proteasomes may interact with chromatin, DNA and other nuclear components.

KEYWORDS:

ADP-ribose; Apoptosis; CTAB-PAGE; Nuclear biology; Proteasome; Ubiquitin

PMID:
25192768
DOI:
10.1016/j.bbapap.2014.08.013
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