CATALYTIC EDITING PROPERTIES OF DNA-POLYMERASES

Enzymatic incorporation of 2',3'-dideoxynucleotides into DNA results in chain termination, We report that 3'-esterified 2'-deoxynucleoside 5'-triphosphates (dNTPs) are false chain-terminator substrates since DNA polymerases, including human immunodeficiency virus reverse transcriptase, can incorporate them into DNA and, subsequently, use this new 3' end to insert the next correctly paired dNTP, Likewise, a DNA substrate with a primer chemically esterified at the 3' position can be extended efficiently upon incubation with dNTPs and T7 DNA polymerase lacking 3'-to-5' exonuclease activity, This enzyme is also able to use dTTP-bearing reporter groups in the 3' position conjugated through amide or thiourea bonds and cleave them to restore a DNA chain terminated by an amino group at the 3' end, Hence, a number of DNA polymerases exhibit wide catalytic versatility at the 3' end of the nascent DNA strand, As part of the polymerization mechanism, these capabilities extend the number of enzymatic activities associated with these enzymes and also the study of interactions between DNA polymerases and nucleotide analogues.