Expansion of repertoire of modified DNAs prepared by PCR using KOD Dash DNA polymerase.

Thymidine analogues bearing a variety of functional groups at the C5-position via an amino-linker arm were prepared and the substrate activity for PCR using thermophilic KOD Dash DNA polymerase was examined. The enzyme accepted the thymidine analogues bearing pyridine, imidazole, biotin, a cationic-charged guanidinium, a cationic-charged amino, mercaptopyridyl and phenanthrolne groups at the C5-position, forming the corresponding PCR product. However, a thymidine analogue bearing a carboxyl group at the C5-position was a poor substrate and the corresponding PCR products could not be obtained. The thymidine analogue bearing a mercapto group was also a poor substrate for the enzyme, because it dimerized by disulfide linkage under PCR conditions. The enzyme hardly accepts the thymidine analogues with a negatively-charged carboxyl group or a bulky group as a substrate. KOD Dash DNA polymerase, having a broader substrate specificity than any other DNA polymerase, will expand the variety of modified DNAs that can be prepared by PCR.

Enzymatic incorporation of chemically-modified nucleotides into DNAs.

Modified 2'-deoxyuridine triphosphates bearing proteinous amino acids at a C5 position were prepared, and their substrate properties were investigated for KOD Dash DNA polymerase during PCR. The modified dUTPs bearing histidyl, lysyl, glutaminyl or seryl group produced the aimed 108 nt PCR products in good yields. In contrast, the analog bearing glutamyl group did not work as a substrate for KOD Dash while the analog bearing aspartyl group gave the product in a low yield. Moreover, not only KOD Dash but also three other thermostable DNA polymerases were tested as catalysts by use of C5 modified dUTPs with two different types of linker arms. Both Pfu and Vent(exo-) were relatively tolerant for the modification at the C5 position as well as KOD Dash.