title: Nuclear proteasomes carry a constitutive posttranslational modification which derails SDS-PAGE (but not CTAB-PAGE).
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.
authors.affiliation: 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.
authors.forename: David S
authors.initials: DS
authors.lastname: Pitcher
authors.affiliation: 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.
authors.forename: Kate
authors.initials: K
authors.lastname: de Mattos-Shipley
authors.affiliation: 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.
authors.forename: Ziming
authors.initials: Z
authors.lastname: Wang
authors.affiliation: 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.
authors.forename: Konstantinos
authors.initials: K
authors.lastname: Tzortzis
authors.affiliation: 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.
authors.forename: Katerina
authors.initials: K
authors.lastname: Goudevenou
authors.affiliation: London Research Institute, Clare Hall Laboratories, Blanche Lane, South Mimms, Potters Bar EN6 3LD, United Kingdom.
authors.forename: Helen
authors.initials: H
authors.lastname: Flynn
authors.affiliation: 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.
authors.forename: Georg
authors.initials: G
authors.lastname: Bohn
authors.affiliation: 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.
authors.forename: Amin
authors.initials: A
authors.lastname: Rahemtulla
authors.affiliation: 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.
authors.forename: Irene
authors.initials: I
authors.lastname: Roberts
authors.affiliation: London Research Institute, Clare Hall Laboratories, Blanche Lane, South Mimms, Potters Bar EN6 3LD, United Kingdom.
authors.forename: Ambrosius P
authors.initials: AP
authors.lastname: Snijders
authors.affiliation: 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.
authors.forename: Anastasios
authors.initials: A
authors.lastname: Karadimitris
authors.affiliation: 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.
authors.forename: Maurits F
authors.initials: MF
authors.lastname: Kleijnen
keywords: ADP-ribose; Apoptosis; CTAB-PAGE; Nuclear biology; Proteasome; Ubiquitin