Ubiquitination histone

Multiubiquitination of intracellular proteins is a prerequisite for the selective degradation of intracellular proteins by the ubiquitin-dependent proteolytic pathway [236,237]. Monoubiquitinated histones are not degraded by the protea-some [238,239]. Proteasome, a multisubunit complex that catalyzes both ubiquitin-dependent and ubiquitin-independent protein degradation, is found in the cytoplasm and nucleus [240-242]. Thus, it is possible that multiubiquitination of the histones may tag these proteins for degradation. 

Ubiquitinated H2A and H2B disappear at metaphase and reappear in anaphase [251-253]. Histone ubiquitination may also be involved in cell cycle progression through S phase [254]. In dividing and non-dividing cells, the ubiquitin moiety of the ubiquitinated histones is in rapid equilibrium with a pool of free ubiquitin [238,239]. The turnover of the ubiquitinated histones is presumably catalyzed by ubiquitin-C-terminal hydrolases. Uni- and multi-cellular eukaryotes contain 

Thermal and chemical cellular stresses result in the rapid disappearance of ubiquitinated histones [258,259]. The levels of ubiquitinated histones drops precipitously after human tumor cells are treated with proteasome inhibitors [260,261]. Deubiquitination of uH2A also occurs during apoptosis, with its lose coinciding with nuclear pyknosis and chromatin condensation [262,263]. 

Chromatin fractionation approaches including ChIP assays have provided evidence for and against uH2A and uH2B being associated with transcriptionally active chromatin [270,281-285]. Most evidence supports uH2A being associated 

Histone ubiquitination and histone methylation-regulatory pathway 

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J. D., Lindsey, G., and Ausio, J. Histone ubiquitination a tagging tail unfolds Bioessays 2002, 24, 166-74. 

Zhang, Y. Transcriptional regulation by histone ubiquitination and deubiquitination. Genes Dev 2003, 17, 2733-40. 

Janknecht R, Nordheim A (1996) MAP kinase-dependent transcriptional coactivation by Elk-1 and its cofactor CBP. Biochem Biophys Res Commun 228 831-837 Jason LJ, Moore SC, Lewis JD, Lindsey G, Ausio J (2002) Histone ubiquitination a tagging tail unfolds Bioessays 24, 166-174... 

The Still limited struetural information on this intriguing post-translational modilieation seems to suggest that at least in the case of uH2A its most important role may be merely informational. Indeed, it has been suggested that histone ubiquitination could label specific chromatin domains [409 11] and as such could be a component of the histone code [121,123,165]. The structural results obtained so far with uH2A nucleosomes and nucleosome arrays clearly support this notion. 

In particular, histones, ubiquitin, myosin, actin, a- and jS-globins, and so on, are systematically recovered on most biological tissue sections. Some of these proteins (human) are listed in the paper by Skold et al. ... 

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