Nucleases specificity

FIGURE 11.32 All example of nuclease specificity The specificity of RNA hydrolysis by bovine pancreatic RNase. This RNase cleaves h at 3 -pyriinidines, yielding oligonncleoddes with pyrimidine 3 -P04 ends. 

Nucleases are enzymes that degrade nucleic acids by cleaving phosphodiester linkages. They may be specific for DNA or RNA, or they may act on both. A nuclease specific for DNA is called a deoxyribonuclease (DNase) and for RNA, ribonuclease (RNase). 

Figure 7-11. Purification ot staphylococcal nuclease by affinity adsorption chromatography on a nuclease-specific agarose column (0.8 x 5 cm). The column was equilibrated with 50mM borate buffer, pH 8.0, containing lOmAf CaClj. Approximately 50 mg of partially purified material containing about 8 mg nuclease was applied in 3.2 ml of the same buffer. After 50 ml of buffer had passed through the column, O.IM acetic acid was added to elute the enzyme. 8.2 mg nuclease and all the original activity was recovered. The flow rate was about 70 ml/hour. [From P. Cuatrecasas, M. Wilchek, and C. B. Anfinsen, Proc. Natl. Acad. Sci. US, 61 636 (1968).]...

Ando, T. (1966) A nuclease specific for heat-denatured DNA isolated from a product of Aspergillus oryzae. Biochim. Biophys. Acta, 114, 158-168. 

RNase A is a small, monomeric enzyme of 124 amino acid residues. The catalytic core is unusually stable to heat and denaturants. RNase A is an endoribo-nuclease specific for pyrimidine bases. The enzyme cleaves phosphodiester bonds of RNA at the 3 side of C and U residues, resulting in mono- and oligoribonucleo-tide products with 3 -P and 5 -OH termini (Scheme 3.2) ... 

Fike most enzymes (see Chapter 14), nucleases exhibit selectivity or specificity for the nature of the substance on which they act. That is, some nucleases act only on DNA (DNases), while others are specific for RNA (the RNases). Still... 

Ribozymes are small RNA molecules with endoribo-nuclease activity. Under appropriate conditions, ribozymes exhibit sequence-specific cleavage of the target. The cleaved mRNA is destabilized and subject to intracellular degradation. 

Kleimnan et al. 2008). In addition, synthetic siRNAs are also subject to degradation in vivo by nuclease activity. Besides side effects and instability, the efficient and specific delivery of the RNAi indncers to the target cell still requires optimization. Here we snmmarize the cnrrent statns of nncleic acid-based antiviral therapentics. The focns will be on antiviral strategies nsing antisense and RNAi technology. Additionally, antiviral ribozymes and aptamers will be discussed briefly, with a focus on recent studies. Gene therapy approaches and delivery systems are the subject of Chapter 11 of this book. 

Fig. 6.3 Molecular model of the domains of the chimeric nuclease (constituted by an hybrid between a non-specific DNA cleavage domain and a zinc finger recognition domain) and DNA. The cleavage domain sits behind...

Restriction endonucleases are at the core of recombinant DNA technology. The specificity of some of these enzymes is described in Chapter 13. Fortunately the restriction endo-nucleases cleave DNA at... 

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