Abstract
A huge diversity of modified nucleobases is used as a tool for studying DNA and RNA. Due to practical reasons, the most suitable positions for modifications are C5 of pyrimidines and C7 of purines. Unfortunately, by using these two positions only, one cannot expand a repertoire of modified nucleotides to a maximum. Here, we demonstrate the synthesis and enzymatic incorporation of novel N4-acylated 2'-deoxycytidine nucleotides (dCAcyl). We find that a variety of family A and B DNA polymerases efficiently use dCAcylTPs as substrates. In addition to the formation of complementary CAcyl•G pair, a strong base-pairing between N4-acyl-cytosine and adenine takes place when Taq, Klenow fragment (exo-), Bsm and KOD XL DNA polymerases are used for the primer extension reactions. In contrast, a proofreading phi29 DNA polymerase successfully utilizes dCAcylTPs but is prone to form CAcyl•A base pair under the same conditions. Moreover, we show that terminal deoxynucleotidyl transferase is able to incorporate as many as several hundred N4-acylated-deoxycytidine nucleotides. These data reveal novel N4-acylated deoxycytidine nucleotides as beneficial substrates for the enzymatic synthesis of modified DNA, which can be further applied for specific labelling of DNA fragments, selection of aptamers or photoimmobilization.