Florence Béranger

Scrapie-like prion protein is translocated to the nuclei of infected cells independently of proteasome inhibition and interacts with chromatin

Prion diseases are fatal transmissible neurodegenerative disorders characterized by the accumulation of an abnormally folded isoform of the cellular prion protein (PrPC) denoted PrPSc. Recently, wild-type and pathogenic PrP mutants have been shown to be degraded by the endoplasmic reticulum-associated degradation proteasome pathway after translocation into the cytosol. We show here that a protease resistant form of PrP accumulated in the nuclei of prion-infected cells independently of proteasome activity, and that this nuclear translocation required an intact microtubule network. Moreover, our results show for the first time that nuclear PrP interacts with chromatin in vivo, which may have physiopathological consequences in prion diseases

A novel Rho GTPase-activating-protein interacts with Gem, a member of the Ras superfamily of GTPases

Gem is a Ras-related protein whose expression is induced in several cell types upon activation by extracellular stimuli. With the aim of isolating the cellular partners of Gem that mediate its biological activity we performed a yeast two-hybrid screen and identified a novel protein of 970 amino acids, Gmip, that interacts with Gem through its N-terminal half, and presents a cysteine-rich domain followed by a Rho GTPase-activating protein (RhoGAP) domain in its C-terminal half. The RhoGAP domain of Gmip stimulates in vitro the GTPase activity of RhoA, but is inactive towards other Rho family proteins such as Rac1 and Cdc42; it is also specific for RhoA in vivo. The same is true for the full-length protein, which is furthermore able to down-regulate RhoA-dependent stress fibres in Ref-52 rat fibroblasts. These findings suggest that the signalling pathways controlled by two proteins of the Ras superfamily, RhoA and Gem, are linked via the action of the RhoGAP protein Gmip (Gem-interacting protein).

Expression of extracellular and intracellular human IFN-γ in mouse L cells transformed with the human IFN-γ cDNA gene

Abstract Cotransformation with a plasmid containing a thymidine kinase gene (pTK2) and a plasmid encoding human IFN-γ (pTG11) has been used to establish murine L cell lines expressing human IFN-γ. The HuIFN-γ gene was present in 30% of the tk+ cell lines and some of these secreted low levels of IFN into the culture medium. Two of the clones obtained after transformation were selected for detailed analysis. Clone 1–12 constitutively secreted very low levels of HuIFN-γ in the culture medium. This antiviral activity was characterized by its species specificity and antigenicity as authentic human IFN-γ In contrast, clone 3–47 produced a HuIFN-γ activity which could only be detected intracellularly. This clone was resistant to infection both by Vesicular stomatitis (VSV) and Mengo viruses and contained increased levels of enzymes known to be induced by interferon. Dur results suggest that clone 3–47 produces a non-secreted HuIFN-γ like molecule which is able to trigger an antiviral state in the murine cell independent of the interaction with a specific IFN-γ surface receptor.