De novo DNA synthesis

DNA polymerases cannot initiate synthesis of a complementary strand of DNA on a totally single-stranded template. Rather, they require an RNA primer—that is, a short, double-stranded region consisting of RNA base-paired to the DNA template, with a free hydroxyl group on the 3 -end of the RNA strand (Figure 29.15). This hydroxyl group serves as the first acceptor of a nucleotide by action of DNA polymerase. In de novo DNA synthesis, that free 3-hydnoxyl is provided by the short stretch of RNA, rather than DNA. 

Enzyme that synthesizes the primer in de novo DNA synthesis... 

Recently, lymphocyte stimulation tests were performed in order to evaluate the immunomodulatory properties of Astragalus saponins. Lymphocyte proliferation or transformation is a process whereby de novo DNA synthesis takes place in response to a mitogen or any other appreciable stimulator (concanavallin A). Astraversianins II, and X, astragalosides I, II, IV and VI and cyclocantosides E and G isolated from A. melanophrurius were able to stimulate mouse lymphocyte proliferation in the concentration range of 0.01-10 (ig/ml. At higher concentration, inhibition of thymidine incorporation was observed [72]. 

P. Carr et al., Protein-mediated error correction for de novo DNA synthesis, Nucleic Acids Research, 32 (20), 2004, e 162. 

Two assays were developed that measure the potency of the FGF-4 transgene carried by Ads FGF-4. In the first case, a one-step growth-promotion assay is conducted on normal, human retinal pigment epithelial cells (ARPE-19). The assay measures metabolic activity (Alamar blue dye metabolism) following infection of ARPE-19 cells with a serial dilution of the virus. The increase in metabohc achvity was measured in relation to a mock-infected control. This increase correlates with FGF-4 produchon determined by an FGF-4 ELISA, increased de-novo DNA synthesis measured by BrdU incorporation, and an increase in cell number. This procedure is therefore an appropriate in-vitro efficacy measure, indicating that the FGF-4 transgene product is biologically active. 

Smith PJ, Paterson MC (1983) Effect of aphidicolin on de novo DNA synthesis, DNA repair and cytotoxicity in gamma-irradiated human fibroblasts Implications for the enhanced radiosensitivity in ataxia telangiectasia. Biochim Biophys Acta 739 17-26... 

Our previous observations using inhibitors of poly(ADP-ribose) polymerase require further studies to elucidate the mechanism by which 3AB is working. It has been demonstrated that SAB has a number of other mechanisms of action, e.g., a reduction in de novo DNA synthesis and glucose oxidation (12, 13). Further studies using additional molecular probes will be needed to address the biochemic basis of radiation sensitivity. 

Ben Yehezkel T, Linshiz G, Buaron H, Kaplan S, Shabi U and,Shapiro E (2008) De novo DNA synthesis using single molecule PCR, Nudeic Acids Res 36 el07. 

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