Commentaries

Ubiquitin crosstalk connecting cellular processes

Tom AM Groothuis² , Nico P Dantuma¹ , Jacques Neefjes² and Florian A Salomons¹

¹  Department of Cell and Molecular Biology, The Medical Nobel Institute, Karolinska Institutet, Von Eulers väg 3, S-17177, Stockholm, Sweden

²  Division of Tumor Biology, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX, Amsterdam, The Netherlands

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Cell Division 2006, 1:21doi:10.1186/1747-1028-1-21

Published:	28 September 2006

Abstract

The polypeptide ubiquitin is used in many processes as different as endocytosis, multivesicular body formation, and regulation of gene transcription. Conjugation of a single ubiquitin moiety is typically used in these processes. A polymer of ubiquitin moieties is required for tagging proteins for proteasomal degradation. Besides its role in protein degradation, ubiquitin is also engaged as mono- or polymer in intracellular signalling and DNA repair. Since free ubiquitin is present in limiting amounts in cells, changes in the demands for ubiquitin in any of these processes is likely to indirectly affect other ubiquitin modifications. For example, proteotoxic stress strongly increases poly-ubiquitylated proteins at the cost of mono-ubiquitylated histones resulting in chromatin remodelling and altered transcription. Here we discuss the interconnection between ubiquitin-dependent processes and speculate on the functional significance of the ubiquitin equilibrium as a signalling route translating cellular stress into molecular responses.