Exonucleolytic digestion

Duplex DNAs with 3 -protruding ends can also be labeled using Pol Ik in a two-step procedure. First, the 3 ends are exonucleolytically digested in the absence of added dNTPs by the 3 — 5 -exonuclease activity and, second, dNTPs containing a labeled nucleotide are provided to start a replacement synthesis. Note that the replacement synthesis method of labeling can be more efficiently performed by the use of T4 DNA Pol whose exonuclease activity is substantially stronger. 

Table 1. Exonucleolytic digestion of duplex AAV circular Monomers...

Exo III is an invaluable tool in recombinant DNA technology because of its exonucleolytic activities that can be used for unidirectional or bidirectional synchronous digestions of dsDNA at controlled rates. 

Bal31 attacks predominantly from the 3 termini. The nucleolytic action on protruding 5 single strands is presumed to involve two successive activities initially an endonuclease activity and subsequently the exonucleolytic activity. During the course of Bal31 digestions of either ssDNA or dsDNA, however, possible intermediary oligonucleotide products have not been observed. 

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