Virus eukaryotic

Structural analysis of the rhinovirus and the hepatitis A virus 3C proteases (Allaire et al. 1994 Matthews et al. 1994) confirmed earlier predictions that the picomavirus 3C proteases are similar to chymotrypsin-Uke serine proteases in their fold. An important difference is that the serine nucleophile of serine proteases is replaced with a cysteine however, the 3C protease is stracturally distinct from the eukaryotic cysteine protease class of enzymes. 

So far as is possible, the discussion in this chapter and in Chapters 37, 38, and 39 will pertain to mammalian organisms, which are, of course, among the higher eukaryotes. At times it will be necessary to refer to observations in prokaryotic organisms such as bacteria and viruses, but in such cases the information will be of a kind that can be extrapolated to mammalian organisms. 

In eukaryotic cells, small DNA elements that clearly are not viruses are capable of transposing themselves in and... 

The multiple sites that serve as origins for DNA replication in eukaryotes are poorly defined except in a few animal viruses and in yeast. However, it is clear that initiation is regulated both spatially and temporaUy, since clusters of adjacent sites initiate rephcation synchronously. There are suggestions that functional domains of chromatin replicate as intact units, implying that the origins of rephcation are specificaUy located with respect to transcription units. 

In addition to the catalytic action served by the snRNAs in the formation of mRNA, several other enzymatic functions have been attributed to RNA. Ribozymes are RNA molecules with catalytic activity. These generally involve transesterification reactions, and most are concerned with RNA metabofism (spfic-ing and endoribonuclease). Recently, a ribosomal RNA component was noted to hydrolyze an aminoacyl ester and thus to play a central role in peptide bond function (peptidyl transferases see Chapter 38). These observations, made in organelles from plants, yeast, viruses, and higher eukaryotic cells, show that RNA can act as an enzyme. This has revolutionized thinking about enzyme action and the origin of life itself. 

Like some eukaryotic viruses (eg, herpes simplex, HIV), some bacterial viruses can either reside in a dormant state within the host chromosomes or can rephcate... 

Deslongchamps and coworkers [26] used a combination of a transannular Diels-Alder cycloaddition and an intramolecular aldol reaction in the synthesis of the unnatural enantiomer of a derivative of the (+)-aphidicolin (4-74), which is a diterpe-noic tetraol isolated from the fungus Cephalosporium aphidicolia. This compound is an inhibitor of DNA polymerase, and is also known to act against the herpes simplex type I virus. In addition, it slows down eukaryotic cell proliferation, which makes it an interesting target as an anticancer agent... 

Monophyly does not fare well either when tested as an alternative explanation for the emergence of early life forms, including noncellular life forms (i.e. viruses).3 For instance, the idea of a monophylic origin of nucleated, or eukaryotic, cells has been more or less broadly rejected and... 

Eukaryote Cell or organism with membrane-bound, structurally discrete nucleus and other well-developed subcellular compartments. Eukaryotes include all organisms except viruses, bacteria, and blue-green algae (see also prokaryote). 

Borman, A. M., and Kean, K. M. (1997). Intact eukaryotic initiation factor 4G is required for hepatitis A virus internal initiation of translation. Virology 237, 129-136. 

Lomakin, I. B., Hellen, C. U., and Pestova, T. V. (2000). Physical association of eukaryotic initiation factor 4G (eIF4G) with eIF4A strongly enhances binding of eIF4G to the internal ribosomal entry site of encephalomyocarditis virus and is required for internal initiation of translation. Mol. Cell Biol. 20, 6019-6029. 

Sizova, D. V., Kolupaeva, V. G., Pestova, T. V., Shatsky, I. N., and Hellen, C. U. (1998). Specific interaction of eukaryotic translation initiation factor 3 with the 5 nontranslated regions of hepatitis C virus and classical swine fever virus RNAs. J. Virol. 72, 4775-4782. 

It would be interesting to know if the mutational consequences of DNA lesions in mammalian cells were the same as those which obtain in bacteria. Methods for retrieving and sequencing mutations in mammalian cells and their viruses are now being developed (81-83) If yeast, a eukaryotic microorganism, can be considered representative of higher eukaryotes, then judging from the observations that the mutational spectra for UV-irradiation and 4-nitroquinoline-l-oxide treatment are identical for yeast (84) and bacteria (85), the spectrum of mutations induced by BPDE in mammalian cells could well resemble those induced in E. coli. 

Kolupaeva, V.G., Fomakin, I.B., Pestova, T.V., and Hellen, C.U.T. (2003) Eukaryotic initiation factors 4G and 4A mediate conformational changes downstream of the initiation codon of the encephalomyocar-ditis virus internal ribosomal entry site. Mol. Cell. Biol. 23, 687-698. 

Markwell, M.A.K., and Fox, C.F. (1978) Surface-specific iodination of membrane proteins of viruses and eukaryotic cells using l,3,4,6-tetrachloro-3a,6a-diphenylglycouril. Biochemistry 17, 4807-4817. 

Compared to the sizes of living cells,1 IUV and LUV resemble the dimensions of enveloped viruses (ranging from 80 to 400 nm) [94], while GUVs resemble typical bacteria and erythrocytes (1-7 pm). Eukaryotic cells tend to be even larger (10-30 pm in animals, 10-100 pm in plants). These dimensions imply that, except for viruses or specific sub-cellular membranes, flat bilayers are the only relevant membrane models. Hence, macroscopically oriented bilayers on solid supports (see... 

There is no doubt that plants represent one of the most productive and yet inexpensive sources of biomass. The absence of contaminating animal pathogens, the eukaryotic translational machinery and the ease of plant virus manipulation make plants... 

Other applications dealt with the development of a luciferin ester substrate to measure the luciferase activity in living cells [141], the detection of toxic compounds such as sodium azide, fluoroacetic acid, and antibiotics [142], the development of a biosensor for the determination of bioavailable mercury [143], the use of eukaryotic luciferases as bacterial markers with different colors of luminescence [144], the determination of complement-mediated killing of bacteria [145], and the development of a bioassay for the determination of HIV type 1 virus and HIV-1 Tat protein activity, valuable also for analysis of HlV-inhibi-tory agents [146],... 

RNAi probably evolved initially in primitive organisms in order to protect their genomes from viruses, transposons and additional insertable genetic elements, and to regulate gene expression. The RNAi pathway was first discovered in plants, but it is now known to function in most, if not all, eukaryotes. 

Mitogen-activated protein kinase phosphatases are dual-function protein phosphatases. Just as the MAPK kinases (e.g. MEKs) are unique as dual-functioning kinases in that they phosphorylate MAPKs on threonine and tyrosine residues, there are unique dual-function ing protein phosphatases that reverse the phosphorylation and activation of MAPKs [43], Such MAPK phosphatases (MKPs) were first identified as a product of vaccinia virus (VH1) and later found in all eukaryotic cells. There are now numerous members of this VH1 family of dual-functioning protein phosphatases. 

Rodriguez, J. M., Salas, M. L., and Vinuela, E. Genes homologous to ubiquitin-conjugating proteins and eukaryotic transcription factor SII in African swine fever virus. Virology 1992, 386, 40-52. 

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