New candidates for true antisense

Structure-activity relationship study of mesyl and busyl phosphoramidate antisense oligonucleotides for unaided and PSMA-mediated uptake into prostate cancer cells

Phosphorothioate (PS) group is a key component of a majority of FDA approved oligonucleotide drugs that increase stability to nucleases whilst maintaining interactions with many proteins, including RNase H in the case of antisense oligonucleotides (ASOs). At the same time, uniform PS modification increases nonspecific protein binding that can trigger toxicity and pro-inflammatory effects, so discovery and characterization of alternative phosphate mimics for RNA therapeutics is an actual task. Here we evaluated the effects of the introduction of several N-alkane sulfonyl phosphoramidate groups such as mesyl (methanesulfonyl) or busyl (1-butanesulfonyl) phosphoramidates into gapmer ASOs on the efficiency and pattern of RNase H cleavage, cellular uptake in vitro, and intracellular localization. Using Malat1 lncRNA as a target, we have identified patterns of mesyl or busyl modifications in the ASOs for optimal knockdown in vitro. Combination of the PSMA ligand-mediated delivery with optimized mesyl and busyl ASOs resulted in the efficient target depletion in the prostate cancer cells. Our study demonstrated that other N-alkanesulfonyl phosphoramidate groups apart from a known mesyl phosphoramidate can serve as an essential component of mixed backbone gapmer ASOs to reduce drawbacks of uniformly PS-modified gapmers, and deserve further investigation in RNA therapeutics.

The Application of Nucleic Acids and Nucleic Acid Materials in Antimicrobial Research

Due to the misuse of antibiotics, multiple drug-resistant pathogenic bacteria have increasingly emerged. This has increased the difficulty of treatment as these bacteria directly affect public health by diminishing the potency of existing antibiotics. Developing alternative therapeutic strategies is the urgent need to reduce the mortality and morbidity related to drug-resistant bacterial infections. In the past 10 to 20 years, nanomedicines have been widely studied and applied as an antibacterial agent. They have become a novel tool for fighting resistant bacteria. The most common innovative substances, metal and metal oxide nanoparticles (NPs), have been widely reported. Until recently, DNA nanostructures were used alone or functionalized with specific DNA sequences by many scholars for antimicrobial purposes which were alternatively selected as therapy for severe bacterial infections. These are a potential candidate for treatments and have a considerable role in killing antibiotic-resistant bacteria. This review involves the dimensions of multidrug resistance and the mechanism of bacteria developing drug resistance. The importance of this article is that we summarized the current study of nano-materials based on nucleic acids in antimicrobial use. Meanwhile, the current progress and the present obstacles for their antibacterial and therapeutic use and special function of stem cells in this field are also discussed.

Towards Zwitterionic Oligonucleotides with Improved Properties: the NAA/LNA-Gapmer Approach

Oligonucleotides (ON) are promising therapeutic candidates, for instance by blocking endogenous mRNA (antisense mechanism). However, ON usually require structural modifications of the native nucleic acid backbone to ensure satisfying pharmacokinetic properties. One such strategy to design novel antisense oligonucleotides is to replace native phosphate diester units by positively charged artificial linkages, thus leading to (partially) zwitterionic backbone structures. Herein, we report a "gapmer" architecture comprised of one zwitterionic central segment ("gap") containing nucleosyl amino acid (NAA) modifications and two outer segments of locked nucleic acid (LNA). This NAA/LNA-gapmer approach furnished a partially zwitterionic ON with optimised properties: i) the formation of stable ON-RNA duplexes with base-pairing fidelity and superior target selectivity at 37 °C; and ii) excellent stability in complex biological media. Overall, the NAA/LNA-gapmer approach is thus established as a strategy to design partially zwitterionic ON for the future development of novel antisense agents.

Mesyl phosphoramidate antisense oligonucleotides as an alternative to phosphorothioates with improved biochemical and biological properties

Forty years of research have shown that antisense oligonucleotides have great potential to target mRNAs of disease-associated genes and noncoding RNAs. Among the vast number of oligonucleotide backbone modifications, phosphorothioate modification is the most widely used in research and the clinic. However, along with their merits are notable drawbacks of phosphorothioate oligonucleotides, including decreased binding affinity to RNA, reduced specificity, and increased toxicity. Here we report the synthesis and in vitro evaluation of the DNA analog mesyl phosphoramidate oligonucleotide. This oligonucleotide type recruits RNase H and shows significant advantages over phosphorothioate in RNA affinity, nuclease stability, and specificity in inhibiting key processes of carcinogenesis. Thus, mesyl phosphoramidate oligonucleotides may be an attractive alternative to phosphorothioates.

Here we describe a DNA analog in which the mesyl (methanesulfonyl) phosphoramidate group is substituted for the natural phosphodiester group at each internucleotidic position. The oligomers show significant advantages over the often-used DNA phosphorothioates in RNA-binding affinity, nuclease stability, and specificity of their antisense action, which involves activation of cellular RNase H enzyme for hybridization-directed RNA cleavage. Biological activity of the oligonucleotide analog was demonstrated with respect to pro-oncogenic miR-21. A 22-nt anti–miR-21 mesyl phosphoramidate oligodeoxynucleotide specifically decreased the miR-21 level in melanoma B16 cells, induced apoptosis, reduced proliferation, and impeded migration of tumor cells, showing superiority over isosequential phosphorothioate oligodeoxynucleotide in the specificity of its biological effect. Lower overall toxicity compared with phosphorothioate and more efficient activation of RNase H are the key advantages of mesyl phosphoramidate oligonucleotides, which may represent a promising group of antisense therapeutic agents.

RNA Interference-Guided Targeting of Hepatitis C Virus Replication with Antisense Locked Nucleic Acid-Based Oligonucleotides Containing 8-oxo-dG Modifications

The inhibitory potency of an antisense oligonucleotide depends critically on its design and the accessibility of its target site. Here, we used an RNA interference-guided approach to select antisense oligonucleotide target sites in the coding region of the highly structured hepatitis C virus (HCV) RNA genome. We modified the conventional design of an antisense oligonucleotide containing locked nucleic acid (LNA) residues at its termini (LNA/DNA gapmer) by inserting 8-oxo-2'-deoxyguanosine (8-oxo-dG) residues into the central DNA region. Obtained compounds, designed with the aim to analyze the effects of 8-oxo-dG modifications on the antisense oligonucleotides, displayed a unique set of properties. Compared to conventional LNA/DNA gapmers, the melting temperatures of the duplexes formed by modified LNA/DNA gapmers and DNA or RNA targets were reduced by approximately 1.6-3.3°C per modification. Comparative transfection studies showed that small interfering RNA was the most potent HCV RNA replication inhibitor (effective concentration 50 (EC50): 0.13 nM), whereas isosequential standard and modified LNA/DNA gapmers were approximately 50-fold less efficient (EC50: 5.5 and 7.1 nM, respectively). However, the presence of 8-oxo-dG residues led to a more complete suppression of HCV replication in transfected cells. These modifications did not affect the efficiency of RNase H cleavage of antisense oligonucleotide:RNA duplexes but did alter specificity, triggering the appearance of multiple cleavage products. Moreover, the incorporation of 8-oxo-dG residues increased the stability of antisense oligonucleotides of different configurations in human serum.

Hairpin ribozyme-antisense RNA constructs can act as molecular Lassos

We have developed a novel class of antisense agents, RNA Lassos, which are capable of binding to and circularizing around complementary target RNAs. The RNA Lasso consists of a fixed sequence derived from the hairpin ribozyme and an antisense segment whose size and sequence can be varied to base pair with accessible sites in the target RNA. The ribozyme catalyzes self-processing of the 5′- and 3′-ends of a transcribed Lasso precursor and ligates the processed ends to produce a circular RNA. The circular and linear forms of the self-processed Lasso coexist in an equilibrium that is dependent on both the Lasso sequence and the solution conditions. Lassos form strong, noncovalent complexes with linear target RNAs and form true topological linkages with circular targets. Lasso complexes with linear RNA targets were detected by denaturing gel electrophoresis and were found to be more stable than ordinary RNA duplexes. We show that expression of a fusion mRNA consisting of a sequence from the murine tumor necrosis factor-α (TNF-α) gene linked to luciferase reporter can be specifically and efficiently blocked by an anti-TNF Lasso. We also show in cell culture experiments that Lassos directed against Fas pre-mRNA were able to induce a change in alternative splicing patterns.

2'-Fluoroarabino- and arabinonucleic acid show different conformations, resulting in deviating RNA affinities and processing of their heteroduplexes with RNA by RNase H

2'-Deoxy-2'-fluoro-arabinonucleic acid (FANA) and arabinonucleic acid (ANA) paired to RNA are substrates of RNase H. The conformation of the natural DNA/RNA hybrid substrates appears to be neither A-form nor B-form. Consistent with this, the conformations of FANA and ANA were found to be intermediate between the A- and B-forms. However, FANA opposite RNA is preferred by RNase H over ANA, and the RNA affinity of FANA considerably exceeds that of ANA. By investigating the conformational boundaries of FANA and ANA residues in crystal structures of A- and B-form DNA duplexes at atomic resolution, we demonstrate that FANA and ANA display subtle conformational differences. The structural data provide insight into the structural requirements at the catalytic site of RNase H. They also allow conclusions with regard to the relative importance of stereoelectronic effects and hydration as modulators of RNA affinity.

Oxetane Locked Thymidine in the Dickerson-Drew Dodecamer Causes Local Base Pairing Distortions—An NMR Structure and Hydration Study

The introduction of a North-type sugar conformation constrained oxetane T block, 1-(1',3'-O-anhydro-beta-D-psicofuranosyl) thymine, at the T(7) position of the self-complementary Dickerson-Drew dodecamer, d[(5'-C(1)G(2)C(3)G(4)A(5)A(6)T(7)T(8)C(9)G(10)C(11)G(12)-3')](2), considerably perturbs the conformation of the four central base pairs, reducing the stability of the structure. UV spectroscopy and 1D NMR display a drop in melting temperature of approximately 10 degrees C per modification for the T(7) oxetane modified duplex, where the T(7) block has been introduced in both strands, compared to the native Dickerson-Drew dodecamer. The three dimensional structure has been determined by NMR spectroscopy and has subsequently been compared with the results of 2.4 ns MD simulations of the native and the T(7) oxetane modified duplexes. The modified T(7) residue is found to maintain its constrained sugar- and the related glycosyl torsion conformations in the duplex, resulting in staggered and stretched T(7).A(6) and A(6).T(7) non-linear base pairs. The stacking is less perturbed, but there is an increased roll between the two central residues compared to the native counterpart, which is compensated by tilts of the neighboring base steps. The one dimensional melting profile of base protons of the T(7) and T(8) residues reveals that the introduction of the North-type sugar constrained thymine destabilizes the core of the modified duplex, promoting melting to start simultaneously from the center as well as from the ends. Temperature dependent hydration studies by NMR demonstrate that the central T(7).A(6)/A(6).T(7) base pairs of the T(7) oxetane modified Dickerson-Drew dodecamer have at least one order of magnitude higher water exchange rates (correlated to the opening rate of the base pair) than the corresponding base pairs in the native duplex.

Removal of the side-chain glucose groups from schizophyllan improves the thermal stability of the polycytidylic acid complexes under the physiological conditions

Thermal stabilization of the complex between polycytidylic acid [poly(C)] and the modified schizophyllan (SPG) whose hydrophilic side-chain glucose groups are selectively removed utilizing mild Smith-degradation has been investigated. With the decrease in the side-chain glucose groups of schizophyllan, the complex with poly(C) can be considerably stabilized compared with unmodified SPG; for example, the T(m) value after the removal of the side-chain glucose groups from 33.3 (unmodified) to 1.0 is enhanced by 14 degrees C. In addition, the thermal stabilization effect is even operative under the physiological conditions ([NaCl] = 0.15 mol dm(-3)). This effect is exerted owing to the construction of the hydrophobic atmosphere around the complex. Although schizophyllan lost the side-chain glucose groups, it still kept the protection effect of the bound poly(C) chain against RNaseA-mediated hydrolysis as observed for unmodified schizophyllan. The assessment of the cytotoxicity for A375:human malignant melanoma, and HL60:human promyelocytic leukemia revealed that the modified schizophyllan scarcely increases the cytotoxicity. These results indicate that the present modification for schizophyllan is of great significance in a viewpoint to develop the practical gene carriers operative even under the physiological conditions.

A structure-activity study of the inhibition of HIV-1 Tat-dependent trans-activation by mixmer 2'-O-methyl oligoribonucleotides containing locked nucleic acid (LNA), alpha-L-LNA, or 2'-thio-LNA residues

The HIV-1 trans-activation responsive element (TAR) RNA stem-loop interacts with the HIV trans-activator protein Tat and other cellular factors to stimulate transcriptional elongation from the viral long terminal repeat (LTR). Inhibitors of these interactions block full-length transcription and, hence, would potentially inhibit HIV replication. We have studied structure-activity relationships in inhibition of trans-activation by steric block 2'-O-methyl (OMe) oligonucleotides chimeras (mixmers) containing locked nucleic acid (LNA) units. Inhibition was measured both in Tat-dependent in vitro transcription from an HIV-1 DNA template directed by HeLa cell nuclear extract and in a robust HeLa cell reporter assay that involves use of stably integrated plasmids to express firefly luciferase Tat dependently and Renilla luciferase Tat-independently. OMe oligonucleotides with optimally 40%-50% LNA units and a minimum of 12 residues in length were active in the cellular assay when delivered with cationic gemini surfactant GS11 at 50% inhibitory concentrations of 230 +/- 40 nM, whereas activity in the in vitro transcription assay was observed down to 9 residues. No cellular activity was observed for OMe oligonucleotides of 12 or 16 residues, which was shown to be due to poor cellular uptake. Both 12-mer mixmers containing alpha -L-LNA or 2'-thio-LNA (S-LNA) were also active in in vitro transcription and the former in cellular reporter inhibition assays, demonstrating that the property of promotion of cellular uptake by LNA is not due to specific sugar conformational effects. Covalent conjugates of OMe/LNA chimeras with Kaposi-fibroblast growth factor (K-FGF) or Transportan peptides failed to enter HeLa cells without a delivery agent but were fully active when delivered by cationic gemini surfactant, showing that in principle, peptide conjugation does not interfere with cellular activity. Thus, OMe/LNA mixmers are powerful reagents for use as steric block inhibitors of gene expression regulated by protein-RNA interactions within HeLa cell nuclei.

The parathyroid hormone mRNA 3'-untranslated region AU-rich element is an unstructured functional element

Parathyroid hormone (PTH) gene expression is regulated post-transcriptionally by hypocalcemia and hypophosphatemia. This regulation is dependent upon binding of protective trans-acting factors to a specific element in the PTH mRNA 3'-untranslated region (UTR). We have previously demonstrated that a 63-nucleotide (nt) AU-rich PTH mRNA element is sufficient to confer regulation of RNA stability by calcium and phosphate in an in vitro degradation assay (IVDA). The 63-nt element consists of a core 26-nt minimal binding sequence and flanking regions. We have now studied the functionality of this element in HEK293 cells using reporter genes and showed that it destabilizes mRNAs for green fluorescent protein (GFP) and growth hormone, similar to its effect in the IVDA. To understand how the cis-element functions as an instability element, we have analyzed its structure by RNase H, primer extension, and computer modeling. The results indicate that the PTH mRNA 3'-UTR and in particular the region of the cis-element are dominated by significant open regions with little folded base pairing. Mutation analysis of the 26-nt core element demonstrated the importance of defined nucleotides for protein-RNA binding. In the GFP reporter system, the same mutations that prevented binding were also ineffective in destabilizing GFP mRNA in HEK293 cells. This is the first study of an AU-rich element that relates function to structure. The PTH mRNA 3'-UTR cis-acting element is an open region that utilizes the distinct sequence pattern to determine mRNA stability by its interaction with trans-acting factors.

Comparison of different antisense strategies in mammalian cells using locked nucleic acids, 2'-O-methyl RNA, phosphorothioates and small interfering RNA

Locked nucleic acids (LNAs) and double-stranded small interfering RNAs (siRNAs) are rather new promising antisense molecules for cell culture and in vivo applications. Here, we compare LNA-DNA-LNA gapmer oligonucleotides and siRNAs with a phosphorothioate and a chimeric 2'-O-methyl RNA-DNA gapmer with respect to their capacities to knock down the expression of the vanilloid receptor subtype 1 (VR1). LNA-DNA-LNA gapmers with four or five LNAs on either side and a central stretch of 10 or 8 DNA monomers in the center were found to be active gapmers that inhibit gene expression. A comparative co-transfection study showed that siRNA is the most potent inhibitor of VR1-green fluorescent protein (GFP) expression. A specific inhibition was observed with an estimated IC50 of 0.06 nM. An LNA gapmer was found to be the most efficient single-stranded antisense oligonucleotide, with an IC50 of 0.4 nM being 175-fold lower than that of commonly used phosphorothioates (IC50 approximately 70 nM). In contrast, the efficiency of a 2'-O-methyl-modified oligonucleotide (IC50 approximately 220 nM) was 3-fold lower compared with the phosphorothioate. The high potency of siRNAs and chimeric LNA-DNA oligonucleotides make them valuable candidates for cell culture and in vivo applications targeting the VR1 mRNA.

Steric inhibition of human immunodeficiency virus type-1 Tat-dependent trans-activation in vitro and in cells by oligonucleotides containing 2'-O-methyl G-clamp ribonucleoside analogues

We report the synthesis of a novel 2'-O-methyl (OMe) riboside phosphoramidite derivative of the G-clamp tricyclic base and incorporation into a series of small steric blocking OMe oligonucleotides targeting the apical stem-loop region of human immunodeficiency virus type 1 (HIV-1) trans- activation-responsive (TAR) RNA. Binding to TAR RNA is substantially enhanced for certain single site substitutions in the centre of the oligonucleotide, and doubly substituted anti-TAR OMe 9mers or 12mers exhibit remarkably low binding constants of <0.1 nM. G-clamp-containing oligomers achieved 50% inhibition of Tat-dependent in vitro transcription at approximately 25 nM, 4-fold lower than for a TAR 12mer OMe oligonucleotide and better than found for any other oligonucleotide tested to date. Addition of one or two OMe G-clamps did not impart cellular trans-activation inhibition activity to cellularly inactive OMe oligonucleotides. Addition of an OMe G-clamp to a 12mer OMe-locked nucleic acid chimera maintained, but did not enhance, inhibition of Tat-dependent in vitro transcription and cellular trans-activation in HeLa cells. The results demonstrate clearly that an OMe G-clamp has remarkable RNA-binding enhancement ability, but that oligonucleotide effectiveness in steric block inhibition of Tat-dependent trans-activation both in vitro and in cells is governed by factors more complex than RNA-binding strength alone.

The potential of antisense as a CNS therapeutic

Antisense offers a precise and specific means of knocking down expression of a target gene, and is a major focus of research in neuroscience and other areas. It has application as a tool in gene function and target validation studies and is emerging as a therapeutic technology in its own right. It has become increasingly obvious, however, that there are a number of hurdles to overcome before antisense can be used effectively in the CNS, most notably finding suitable nucleic acid chemistries and an effective delivery vehicle to transport antisense oligonucleotides (AS-ODNs) across the blood-brain barrier (BBB) to their site of action. Despite these problems, a number of potential applications of AS-ODNs in CNS therapeutics have been validated in vitro and, in some cases, in vivo. Here the authors outline available nucleic acid chemistries and review progress in the development of non-invasive delivery vehicles that may be applicable to CNS therapeutics. Further to this, they discuss a number of experimental applications of AS-ODNs to CNS research and speculate on the development of antisense techniques to treat CNS disease.

LNA: a versatile tool for therapeutics and genomics

Locked nucleic acid (LNA) is a nucleic acid analogue that displays unprecedented hybridization affinity towards complementary DNA and RNA. Structural studies have shown LNA to be an RNA mimic, fitting seamlessly into an A-type duplex geometry. Several reports have revealed LNA as a most promising molecule for the development of oligonucleotide-based therapeutics. For example, Tat-dependent transcription and telomerase activity have been efficiently suppressed by LNA oligomers, and efficient cleavage of highly structured RNA has been achieved using LNA-modified DNAzymes ('LNAzyme'). Furthermore, convincing examples of the application of LNA to nucleic acid diagnostics have been reported, including high capturing efficiencies and unambiguous scoring of single-nucleotide polymorphisms.

Antisense oligonucleotides targeted to the domain IIId of the hepatitis C virus IRES compete with 40S ribosomal subunit binding and prevent in vitro translation

Initiation of protein synthesis on the hepatitis C virus (HCV) mRNA involves a structured element corresponding to the 5' untranslated region and constituting an internal ribosome entry site (IRES). The domain IIId of the HCV IRES, an imperfect RNA hairpin extending from nucleotides 253 to 279 of the viral mRNA, has been shown to be essential for translation and for the binding of the 40S ribosomal subunit. We investigated the properties of a series of antisense 2'-O-methyloligoribonucleotides targeted to various portions of the domain IIId. Several oligomers, 14-17 nt in length, selectively inhibited in vitro translation of a bicistronic RNA construct in rabbit reticulocyte lysate with IC(50)s <10 nM. The effect was restricted to the second cistron (the Renilla luciferase) located downstream of the HCV IRES; no effect was observed on the expression of the first cistron (the firefly luciferase) which was translated in a cap-dependent manner. Moreover, antisense 2'-O-methyloligoribonucleotides specifically competed with the 40S ribosomal subunit for binding to the IRES RNA in a filter- retention assay. The antisense efficiency of the oligonucleotides was nicely correlated to their affinity for the IIId subdomain and to their ability to displace 40S ribosomal subunit, making this process a likely explanation for in vitro inhibition of HCV-IRES-dependent translation.

Loop-loop interaction of HIV-1 TAR RNA with N3'-->P5' deoxyphosphoramidate aptamers inhibits in vitro Tat-mediated transcription

A hairpin RNA aptamer has been identified by in vitro selection against the transactivation-responsive element (TAR) of HIV-1. A nuclease-resistant N3' --> P5' phosphoramidate isosequential analog of this aptamer also folds as a hairpin and forms with TAR a loop-loop "kissing" complex with a binding constant in the low nanomolar range as demonstrated by electrophoretic mobility-shift assays and surface plasmon resonance experiments. The key structural determinants, which contribute to the stability of the RNA aptamer-TAR complex, loop complementarity and the GA residues closing the aptamer loop, remain crucial for the N3' --> P5' aptamer-TAR complex. Moreover, the N3' --> P5' phosphoramidate aptamer specifically interferes with the binding of a peptide derived from the transactivator protein (Tat) peptide to TAR and selectively inhibits the Tat-mediated transcription in an in vitro assay, which marks this nuclease-resistant aptamer as a relevant candidate for experiments in cells.

Utilization of antisense oligonucleotides to study the role of 5-cytosine DNA methyltransferase in cellular transformation and oncogenesis

A large body of data point toward 5-cytosine DNA methyltransferase 1 (DNMT1) as a critical component of oncogenic programs. The study of the role of DNMT1 in cancer has been hindered by the lack of specific inhibitors. A different approach to study the role of DNMT1 in cancer is to use sequence-specific antisense oligonucleotides against DNMT1 mRNA. This paper discusses methods used to identify sequence-specific antisense oligonucleotides and to assess their DNA methylation inhibitory properties. Antisense oligonucleotides are applied to determine whether DNMT1 plays a causal role in specific cancer models ex vivo as well as in vivo.

Design of antisense oligonucleotides stabilized by locked nucleic acids

The design of antisense oligonucleotides containing locked nucleic acids (LNA) was optimized and compared to intensively studied DNA oligonucleotides, phosphorothioates and 2'-O-methyl gapmers. In contradiction to the literature, a stretch of seven or eight DNA monomers in the center of a chimeric DNA/LNA oligonucleotide is necessary for full activation of RNase H to cleave the target RNA. For 2'-O-methyl gapmers a stretch of six DNA monomers is sufficient to recruit RNase H. Compared to the 18mer DNA the oligonucleotides containing LNA have an increased melting temperature of 1.5-4 degrees C per LNA depending on the positions of the modified residues. 2'-O-methyl nucleotides increase the T(m) by only <1 degree C per modification and the T(m) of the phosphorothioate is reduced. The efficiency of an oligonucleotide in supporting RNase H cleavage correlates with its affinity for the target RNA, i.e. LNA > 2'-O-methyl > DNA > phosphorothioate. Three LNAs at each end of the oligonucleotide are sufficient to stabilize the oligonucleotide in human serum 10-fold compared to an unmodified oligodeoxynucleotide (from t(1/2) = approximately 1.5 h to t(1/2) = approximately 15 h). These chimeric LNA/DNA oligonucleotides are more stable than isosequential phosphorothioates and 2'-O-methyl gapmers, which have half-lives of 10 and 12 h, respectively.

Telomerase - strategies to exploit an important chemotherapeutic target

Telomeres, unique protein-DNA complexes located at the chromosome ends, have important functions involving both DNA protection and cellular signalling. Telomere structure is very dynamic yet tightly controlled. One important factor is the presence of telomerase, a telomere-specific DNA polymerase activated in a majority of cancer cells. Cancer and normal cell telomeres may have dissimilar structures due to variances in telomere length, telomerase activity and levels of telomere binding proteins. In designing compounds to strictly target cancer cells, these distinctions should be investigated. Much of the recent focus has been on the development of highly effective telomerase inhibitors. Another novel group of small molecules target telomere DNA, thereby disrupting both telomerase activity and telomere structure. This class of compounds should have an immediate impact on cell growth and viability. Since many molecular characteristics of telomeres are unknown, small molecules should also be useful in probing differences in telomere dynamics unique to cancer cells.