Renata Kaczmarek

Histidine triad nucleotide-binding protein 1 (HINT-1) phosphoramidase transforms nucleoside 5'-O-phosphorothioates to nucleoside 5'-O-phosphates.

Nucleoside 5′-O-phosphorothioates are formed in vivo as primary products of hydrolysis of oligo(nucleoside phosphorothioate)s (PS-oligos) that are applied as antisense therapeutic molecules. The biodistribution of PS-oligos and their pharmacokinetics have been widely reported, but little is known about their subsequent decay inside the organism. We suggest that the enzyme responsible for nucleoside 5′-O-monophosphorothioate ((d)NMPS) metabolism could be histidine triad nucleotide-binding protein 1 (Hint-1), a phosphoramidase belonging to the histidine triad (HIT) superfamily that is present in all forms of life. An additional, but usually ignored, activity of Hint-1 is its ability to catalyze the conversion of adenosine 5′-O-monophosphorothioate (AMPS) to 5′-O-monophosphate (AMP). By mutagenetic and biochemical studies, we defined the active site of Hint-1 and the kinetic parameters of the desulfuration reaction (P-S bond cleavage). Additionally, crystallographic analysis (resolution from 1.08 to 1.37 Å) of three engineered cysteine mutants showed the high similarity of their structures, which were not very different from the structure of WT Hint-1. Moreover, we found that not only AMPS but also other ribonucleoside and 2′-deoxyribonucleoside phosphorothioates are desulfurated by Hint-1 at the following relative rates: GMPS > AMPS > dGMPS ≥ CMPS > UMPS > dAMPS ≫ dCMPS > TMPS, and during the reaction, hydrogen sulfide, which is thought to be the third gaseous mediator, was released.

Tetra-Thymidine Phosphorofluoridates via Tetra-Thymidine Phosphoro-selenoates: Synthesis and Stability

Abstract Tetra-thymidine phosphoroselenoates obtained via phosphoramidite methodology with bis(di-O,O-isopropyl phosphinothioyl)diselenide as oxidising reagent, under treatment with iodine and triethylamine tris(hydrofluoride) (TAF) provide a diastereomeric mixture of tetra-thymidine phosphorofluoridates whose hydrotytic stability was studied by HPLC.

Conjugation of amino acid O-methyl esters with AZT-5′-O-phosphorothioate and phosphorodithioate

Abstract Based upon 1,3,2-oxathia(-dithia)phospholane chemistry, 5′- O -derivatisation of AZT with the O -methyl esters of l -phenylalanine and l -tryptophan was performed and the corresponding 5′-aminoacidophosphoramidothioates or phosphoramidodithioates of AZT were obtained in satisfactory yield.

Evaluation of influence of Ap4A analogues on Fhit-positive HEK293T cells; cytotoxicity and ability to induce apoptosis.

Fragile histidine triad (Fhit) protein encoded by tumour suppressor FHIT gene is a proapoptotic protein with diadenosine polyphosphate (Ap(n)A, n=2-6) hydrolase activity. It has been hypothesised that formation of Fhit-substrate complex results in an apoptosis initiation signal while subsequent hydrolysis of Ap(n)A terminates this action. A series of Ap(n)A analogues have been identified in vitro as strong Fhit ligands [Varnum, J. M.; Baraniak, J.; Kaczmarek, R.; Stec, W. J.; Brenner, C. BMC Chem. Biol.2001, 1, 3]. We assumed that in Fhit-positive cells these compounds might preferentially bind to Fhit and inhibit its hydrolytic activity what would prolong the lifetime of apoptosis initiation signalling complex. Therefore, several Fhit inhibitors were tested for their cytotoxicity and ability to induce apoptosis in Fhit-positive HEK293T cells. These experiments have shown that Ap(4)A analogue, containing a glycerol residue instead of the central pyrophosphate and two terminal phosphorothioates [A(PS)-CH(2)CH(OH)CH(2)-(PS)A (1)], is the most cytotoxic among test compounds (IC(50)=17.5±4.2 μM) and triggers caspase-dependent cell apoptosis. The Fhit-negative HEK293T cells (in which Fhit was silenced by RNAi) were not sensitive to compound 1. These results indicate that the Ap(4)A analogue 1 induces Fhit-dependent apoptosis and therefore, it can be considered as a drug candidate for anticancer therapy in Fhit-positive cancer cells and in Fhit-negative cancer cells, in which re-expression of Fhit was accomplished by gene therapy.

NEW APPROACH TO THE SOLID PHASE SYNTHESIS OF N3'P5' PHOSPHORAMIDATE OLIGONUCLEOTIDES

Abstract LCA-CPG-nucleoside 5′-O-(O-β-cyanoethyl-H-phosphonates) react with 3′-amino-2′,3′-dideoxynucleoside in the presence of iodine giving in a high yield N3′→P5′ phosphoramidate oligonucleotides.

Crystallographic studies of the complex of human HINT1 protein with a non-hydrolyzable analog of Ap4A.

Histidine triad nucleotide-binding protein 1 (HINT1) represents the most ancient and widespread branch in the histidine triad proteins superfamily. HINT1 plays an important role in various biological processes, and it has been found in many species. Here, we report the first structure (at a 2.34Å resolution) of a complex of human HINT1 with a non-hydrolyzable analog of an Ap4A dinucleotide, containing bis-phosphorothioated glycerol mimicking a polyphosphate chain, obtained from a primitive monoclinic space group P21 crystal. In addition, the apo form of hHINT1 at the space group P21 refined to 1.92Å is reported for comparative studies.

Stereochemical analysis of diastereomeric 1,3-bis(adenosine-5'-O-phosphorothioyl)glycerols.

We have published recently that 1,3-bis(adenosine-50-phosphorothioyl)glycerol (1), prepared according to the oxathiaphospholane methodology possesses stronger inhibitory activity towards FHIT protein, as compared with all known inhibitors. Fhit protein is the Ap3A hydrolase which binds and cleaves diadenosine polyphosphates and acts as a tumor suppressor. Loss of Fhit protein is among the earliest known events in the development of a variety of the most common and lethal human malignancies. Function of Fhit in tumor suppression does not require diadenosine polyphosphates cleavage but correlates with the ability to form enzyme-substrate complexes. If Fhit-substrate complexes promote tumor suppression by stimulating a pro-apoptotic effector, then Fhit inhibitors, that resemble natural substrates, may promote or antagonize Fhit function, depending on their features, in Fhit þ cells. NUCLEOSIDES, NUCLEOTIDES & NUCLEIC ACIDS Vol. 22, Nos. 5–8, pp. 797–799, 2003

Synthesis and an Antiviral Activity Evaluation of Nucleoside 5′-O-(N-acyl) Phosphoramidates

Background: Pyrimidine nucleoside analogues represent an established class of clinically useful antiviral agents. Once inside the cell, they are activated by a series of intracellular phosphorylation steps to produce 5′-triphosphate derivatives. In many cases, nucleoside analogues are poor substrates for the cellular kinases needed for their activation. It is clear that intracellular introduction of nucleoside analogues as phosphorylated metabolites (so called pronucleotides) could circumvent difficulties associated with the use of non-phosphorylated nucleoside analogues. Methods: Among the current diverse pronucleotide approaches, nucleoside phosphoramidate derivatives appear to be an interesting class of potential antiviral agents because of the known relatively low stability of the P–N bond in cellular media. On the basis of oxathiaphospholane chemistry, a series of novel conjugates of 5′-O-phosphorylated zidovudine (AZT) and stavudine (d4T) with amino acids carboxamidates were obtained. The synthesis was performed using N-(2-thiono-1,3,2-oxathiaphospholane) derivatives of amino acids carboxamides as precursors. Results: All synthesized compounds were studied against DNA and RNA viruses. Specific antiviral activities were only detected against HIV type-1 and HIV type-2 in MT-4 cell cultures at compound concentrations that were equally active or slightly inferior to the activity of their parent drugs (2- to 20-fold for the AZT prodrugs and 6- to 40-fold for the d4T prodrugs). The compounds were also evaluated for their anti-HIV activity in CEM and in CEM thymidine-kinase-deficient (CEM/TK−) cell cultures. Conclusions: Loss of compound antiviral potency in the CEM/TK− cells suggested an eventual conversion of the test compounds to the free nucleosides prior to further phosphorylation to the active 5′-triphosphate metabolite.

Organometallic Nucleosides: Synthesis and Biological Evaluation of Substituted Dicobalt Hexacarbonyl 2′-Deoxy-5-oxopropynyluridines

Abstract Reactions of dicobalt octacarbonyl [Co2(CO)8] with 2′‐deoxy‐5‐oxopropynyluridines and related compounds gave dicobalt hexacarbonyl nucleoside complexes (83–31 %). The synthetic outcomes were confirmed by X‐ray structure determination of dicobalt hexacarbonyl 2′‐deoxy‐5‐(4‐hydroxybut‐1‐yn‐1‐yl)uridine, which exhibits intermolecular hydrogen bonding between a modified base and ribose. The electronic structure of this compound was characterized by the DFT calculations. The growth inhibition of HeLa and K562 cancer cell lines by organometallic nucleosides was examined and compared to that by alkynyl nucleoside precursors. Coordination of the dicobalt carbonyl moiety to the 2′‐deoxy‐5‐alkynyluridines led to a significant increase in the cytotoxic potency. The cobalt compounds displayed antiproliferative activities with median inhibitory values (IC50) in the range of 20 to 80 μm for the HeLa cell line and 18 to 30 μm for the K562 cell line. Coordination of an acetyl‐substituted cobalt nucleoside was expanded by using the 1,1‐bis(diphenylphosphino)methane (dppm) ligand, which exhibited cytotoxicity at comparable levels. The formation of reactive oxygen species in the presence of cobalt compounds was determined in K562 cells. The results indicate that the mechanism of action for most antiproliferative cobalt compounds may be related to the induction of oxidative stress.

A Novel Approach to the Preparationof Peptide-Oligonucleotide Conjugates

A novel approach to the synthesis of peptide-oligonucleotide conjugates (POC) based on the oxathiaphospholane chemistry has been developed. Peptide and oligonucleotide fragments, which were separately prepared, were linked postsynthetically by the functionalization of the peptide either by attachment of the oxathiaphospholane residue directly at the N-terminus or at the hydroxy group of the linker connected to N-terminus. The conjugation reaction, based on DBU-assisted nucleophilic attack of hydroxy group of oligonucleotide on phosphorus atom in the oxathiaphospholane derivatives of peptide, furnished the desired POC.