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Abstract: Polyglutamine diseases are a group of pathologies affecting different parts of the brain and causing dysfunction and atrophy of certain neural cell populations. These diseases stem from mutations in various cellular genes that result in the synthesis of proteins with extended polyglutamine tracts. In particular, this concerns huntingtin, ataxins, and androgen receptor. These mutant proteins can form oligomers, aggregates, and, finally, aggresomes with distinct functions and different degrees of cytotoxicity. In this review, we analyze the effects of different forms of polyQ proteins on other proteins and their functions, which are considered as targets for therapeutic intervention. [Copyright &y& Elsevier]

Abstract: As predicted by systems biology, a paradigm shift will emerge through the integration of information about different layers of cellular processes. The cell cycle network is at the heart of the cellular computing system, and orchestrates versatile cellular functions. The NIRF/UHRF2 ubiquitin ligase is an “intermodular hub” that occupies a central position in the network, and facilitates coordination among the cell cycle machinery, the ubiquitin–proteasome system, and the epigenetic system. NIRF interacts with cyclins, CDKs, p53, pRB, PCNA, HDAC1, DNMTs, G9a, methylated histone H3 lysine 9, and methylated DNA. NIRF ubiquitinates cyclins D1 and E1, and induces G1 arrest. The NIRF gene is frequently lost in tumors and is a candidate tumor suppressor, while its paralog, the UHRF1 gene, is hardly altered. Thus, investigations of NIRF are essential to understand the entire biological systems. Through integration of the enormous information flows, NIRF may contribute to the coupling between the cell cycle network and the epigenetic landscape. We propose the new paradigm that NIRF produces the extreme diversity in the network wiring that helps the diversity of Waddington’s canals. [Copyright &y& Elsevier]

Anomalous expansion of a polyglutamine (polyQ) tract in the protein ataxin-3 causes spinocerebellar ataxia type 3, an autosomal dominant neurodegenerative disease. Very little is known about the structure and the function of ataxin-3, although this information would undoubtedly help to understand why the expanded protein forms insoluble nuclear aggregates and causes neuronal cell death. With the aim of establishing the domain architecture of ataxin-3 and the role of the polyQ tract within the protein context, we have studied the human and murine orthologues using a combination of techniques, which range from limited proteolysis to circular dichroism (CD) and nuclear magnetic resonance (NMR) spectroscopies. The two protein sequences share a highly conserved N-terminus and differ only in the length of the glutamine repeats and in the C-terminus. Our data conclusively indicate that ataxin-3 is composed by a structured N-terminal domain, followed by a flexible tail. Moreover, [15N]glutamine selectively labelled samples allowed us to have a direct insight by NMR into the structure of the polyQ region. [Copyright &y& Elsevier]