Mediator complex mammalian

Examples of co-activators are the steroid receptor co-activator (SRC) family [48] and the components of the mammalian mediator complex, which possesses chromatin remodelling ability and tethers activated steroid hormone receptors to the basal transcription machinery [49]. Additional co-... 

Polyphenol oxidase occurs within certain mammalian tissues as well as both lower (46,47) and higher (48-55) plants. In mammalian systems, the enzyme as tyrosinase (56) plays a significant role in melanin synthesis. The PPO complex of higher plants consists of a cresolase, a cate-cholase and a laccase. These copper metalloproteins catalyze the one and two electron oxidations of phenols to quinones at the expense of 02. Polyphenol oxidase also occurs in certain fungi where it is involved in the metabolism of certain tree-synthesized phenolic compounds that have been implicated in disease resistance, wound healing, and anti-nutrative modification of plant proteins to discourage herbivory (53,55). This protocol presents the Triton X-114-mediated solubilization of Vida faba chloroplast polyphenol oxidase as performed by Hutcheson and Buchanan (57). 

Ignatovich lA, Dizhe EB, Pavlotskaya AV, et al. Complexes of plasmid DNA with basic domain 47-57 of the HlV-1 Tat protein are transferred to mammalian cells by endocytosis-mediated pathways. J Biol Chem 2003 278(43) 42625-42636. 

Fig. 4. Domain structure of mammalian DNA methyltransferases. (a) The domain structure of the known DNA methyltransferases, depicting the conserved catalytic domain (dark box) and other identified domains. Conserved aminoacid motifs in the catalytic domain are shown in lighter shade of gray. (b) Schematic representation of the reported protein-protein interactions of Dnmtl with a number of regulatory proteins interactions that modulate Dnmtl methyitransferase activity (darker rectangles) or mediate methylation-independent transcriptional repression mechanisms (lighter rectangles). When Dnmtl represses transcription through its enzymatic activity, it has been described to interact with some proteins PCNA [37] and an oncogenic transcription factor PML-RAR [25]. Note that in the case of the PML-RAR transcription factor, histone deacetylase 1 (HDACl) is also bound to the complex. When Dnmtl represses transcription via methylation-independent pathways, it binds to HDACs either directly [34] or indirectly through other proteins the corepressor DMAPl [33], the retinoblastoma protein, and a gene-specific transcription factor [31].

An additional virus, which has more recently gained some attention as a possible vector, is that of the sindbis virus. A member of the alphavirus family, this ssRNA virus can infect a broad range of both insect and vertebrate cells. The mature virion particles consist of the RNA genome complexed with a capsid protein C. This, in turn, is enveloped by a lipid bilayer in which two additional viral proteins, El and E2, are embedded. The E2 polypeptide appears to mediate viral binding to the surface receptors of susceptible cells (the major mammalian cell surface receptor it targets appears to be the highly conserved, widely distributed laminin receptor). 

There is a wide variety of vectors used to deliver DNA or oligonucleotides into mammalian cells, either in vitro or in vivo. The most common vector systems are based on viral [retroviruses (9, 10), adeno-associated virus (AAV) (11), adenovirus (12, 13), herpes simplex virus (HSV) (14)] andnonviral [cationic liposomes (15,16), polymers and receptor-mediated polylysine-DNA] complexes (17). Other viral vectors that are currently under development are based on lentiviruses (18), human cytomegalovirus (CMV) (19), Epstein-Barr virus (EBV) (20), poxviruses (21), negative-strand RNA viruses (influenza virus), alphaviruses and herpesvirus saimiri (22). Also a hybrid adenoviral/retroviral vector has successfully been used for in vivo gene transduction (23). A simplified schematic representation of basic human gene therapy methods is described in Figure 13.1. 

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