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2′-Deoxyadenosine substituted at C-8 by a propylthio group was introduced into oligodeoxyribonucleotides by solid phase synthesis. Oxidation by potassium persulfate (oxone) occurred selectively on the sulfur containing nucleoside causing a weakening of the glycosidic bond. Subsequent hydrolytic treatment led to selective removal of the modified base and generation of an abasic site. This constitutes a novel and convenient route for the chemical synthesis of oligodeoxyribonucleotides containing an abasic site at a preselected position in the sequence.

Molecules 2-5 that include in their structure a biotin moiety as detectable unit and differently substituted phenyl diazo functions as reactive group were prepared as reagents for labeling the phosphate group in mono and polynucleotides. These molecules were shown to react selectively and quantitatively with the model nucleotide 3'-UMP. They were used successfully in the labeling step of DNA and RNA analysis using high-density DNA-chips (or microarrays) technology.

The three nucleoside triphosphates 1, 2 and 3 bearing a linker with a terminal methylketone group were prepared for incorporation into RNA fragments and post-labelling by the fluorescein derivative 4 containing an aminooxy group.

In a search for more active radioprotective compounds, we have prepared and examined a series of model molecules in which the radioprotective beta-aminothiol unit (free or derivatized as acetate or phosphorothioate) is tethered to the DNA-binding chromophores quinoline and acridine through links of variable length. The modifying activity of these 'hybrid' molecules was estimated by measuring the formation of 8-oxo-2'-deoxyguanosine (8-oxodGuo) in double-strand DNA upon exposure to gamma-rays in oxygen-free solution in the presence of the drugs. We show that all hybrid molecules protect the guanine moiety from oxidation more efficiently than the parent beta-aminothiol units. The degree of protection is the highest for the molecules in which the thiol is linked to the strong binding intercalator acridine through a long polyaminochain.

We have prepared a series of tailor-made molecules that recognize and cleave DNA at apurinic sites in vitro. These molecules incorporate in their structure different units designed for specific function: an intercalator for DNA binding, a nucleic base for abasic site recognition and a linking chain of variable length and nature (including amino and/or amido functions). The cleavage efficiency of the molecules can be modulated by varying successively the nature of the intercalating agent, the nucleic base and the chain. All molecules bind to native calf thymus DNA with binding constants ranging from 10(4) to 10(6) M-1. Their cleavage activity was determined on plasmid DNA (pBR 322) containing 1.8 AP-sites per DNA-molecule. The minimum requirements for cleavage are the presence of the three units, the intercalator, the nucleic base and at least one amino function in the chain. The most efficient molecules cleave plasmid DNA at nanomolar concentrations. Enzymatic experiments on the termini generated after cleavage of AP-DNA suggest a strand break induced by a beta-elimination reaction. In order to get insight into the mode of action (efficiency, selectivity, interaction), we have used synthetic oligonucleotides containing either a true abasic site at a determined position to analyse the cleavage parameters of the synthetic molecules by HPLC or a chemically stable analog (tetrahydrofuran) of the abasic site for high field 1H NMR spectrometry and footprinting experiments. All results are consistent with a beta-elimination mechanism in which each constituent of the molecule exerts a specific function as indicated in the scheme: DNA targeting, abasic site recognition, phosphate binding and beta-elimination catalysis.(ABSTRACT TRUNCATED AT 250 WORDS)

A new class of affinity labels has been developed for human DNA (cytosine-5) methyltransferases. These oligodeoxynucleotides contain 5-fluorodeoxycytidine at a mispair within the recognition motif of the human enzyme. They were not effectively recognized by bacterial methyltransferases. They can be viewed as analogs of the intermediates transiently produced by methyltransferases during catalysis. Affinity labelling patterns suggest that both the structurally induced activity and the methyl-directed activity of the human enzymes operate by the same mechanism and reside on the same polypeptide chains.

The hydrolytic stability of 2′-deoxypurine nucleosides is decreased by introduction of electron-withdrawing substituents at the C-8 position in the series of compounds 2–8 , 10–14 . The sulfone group causes a 2.9 × 10 4 rate acceleration for glycosidic bond cleavage in compound 14 .

A series of bifunctional molecules in which a heterocycle is linked to an aminothiol chain were synthesized. A new synthesis of N,N′-bis-(3-aminopropyl) cystamine (WR 33278) is described. Reaction of WR 33278 or analogues with the phenoxy derivatives of quinoline or acridine yielded the desired bifunctional molecules.

Preparation of the uridine and adenosine triphosphates 1 and 2 bearing a linker with a terminal aminooxy group is described. Both 1 and 2 react readily with the aldehydic fluorescein derivative 15. They could each be incorporated into a 330-mer fragment with T7 RNA polymerase.