2-Formyl-dATP as Substrate for Polymerase Synthesis of Reactive DNA Bearing an Aldehyde Group in the Minor Groove.

2-Formyl-2'-deoxyadenosine triphosphate (dCHO ATP) was synthesized and tested as a substrate in enzymatic synthesis of DNA modified in the minor groove with a reactive aldehyde group. The multistep synthesis of dCHO ATP was based on the preparation of protected 2-dihydroxyethyl-2'-deoxyadenosine intemediate, which was triphosphorylated and converted to aldehyde through oxidative cleavage. The dCHO ATP triphosphate was a moderate substrate for KOD XL DNA polymerase, and was used for enzymatic synthesis of some sequences using primer extension (PEX). On the other hand, longer sequences (31-mer) with higher number of modifications, or sequences with modifications at adjacent positions did not give full extension. Single-nucleotide extension followed by PEX was used for site-specific incorporation of one aldehyde-linked adenosine into a longer 49-mer sequence. The reactive formyl group was used for cross-linking with peptides and proteins using reductive amination and for fluorescent labelling through oxime formation with an AlexaFluor647-linked hydroxylamine.

Reactive modifications of DNA nucleobases for labelling, bioconjugations, and cross-linking.

Modification of DNA with reactive groups and their post-synthetic transformations are useful for labelling, imaging, bioconjugations and cross-linking with other (bio)molecules. This review summarizes the recent progress in this field and covers transformations of oxo groups, cycloadditions, conjugate additions, alkylations, cross-couplings and other reactions. Examples of applications are given and the practicability and scope of the reactions are discussed.

Squaramate-Modified Nucleotides and DNA for Specific Cross-Linking with Lysine-Containing Peptides and Proteins.

Squaramate-linked 2'-deoxycytidine 5'-O-triphosphate was synthesized and found to be good substrate for KOD XL DNA polymerase in primer extension or PCR synthesis of modified DNA. The resulting squaramate-linked DNA reacts with primary amines to form a stable diamide linkage. This reaction was used for bioconjugations of DNA with Cy5 and Lys-containing peptides. Squaramate-linked DNA formed covalent cross-links with histone proteins. This reactive nucleotide has potential for other bioconjugations of nucleic acids with amines, peptides or proteins without need of any external reagent.