A Biotinylated cpFIT-PNA Platform for the Facile Detection of Drug Resistance to Artemisinin in Plasmodium falciparum

The evolution of drug resistance to many antimalarial drugs in the lethal strain of malaria (Plasmodium falciparum) has been a great concern over the past 50 years. Among these drugs, artemisinin has become less effective for treating malaria. Indeed, several P. falciparum variants have become resistant to this drug, as elucidated by specific mutations in the pfK13 gene. This study presents the development of a diagnostic kit for the detection of a common point mutation in the pfK13 gene of P. falciparum, namely, the C580Y point mutation. FIT-PNAs (forced-intercalation peptide nucleic acid) are DNA mimics that serve as RNA sensors that fluoresce upon hybridization to their complementary RNA. Herein, FIT-PNAs were designed to sense the C580Y single nucleotide polymorphism (SNP) and were conjugated to biotin in order to bind these molecules to streptavidin-coated plates. Initial studies with synthetic RNA were conducted to optimize the sensing system. In addition, cyclopentane-modified PNA monomers (cpPNAs) were introduced to improve FIT-PNA sensing. Lastly, total RNA was isolated from red blood cells infected with P. falciparum (WT strain - NF54-WT or mutant strain - NF54-C580Y). Streptavidin plates loaded with either FIT-PNA or cpFIT-PNA were incubated with the total RNA. A significant difference in fluorescence for mutant vs WT total RNA was found only for the cpFIT-PNA probe. In summary, this study paves the way for a simple diagnostic kit for monitoring artemisinin drug resistance that may be easily adapted to malaria endemic regions.

Correction: Cyclopentane FIT-PNAs: bright RNA sensors

Correction for 'Cyclopentane FIT-PNAs: bright RNA sensors' by Odelia Tepper et al., Chem. Commun., 2021, 57, 540-543, https://doi.org/10.1039/D0CC07400D.

FIT-PNAs as RNA-Sensing Probes for Drug-Resistant Plasmodium falciparum

Detecting RNA at single-nucleotide resolution is a formidable task. Plasmodium falciparum is the deadliest form of malaria in humans and has shown to gain resistance to essentially all antimalarial drugs including artemisinin and chloroquine. Some of these drug resistances are associated with single-nucleotide polymorphisms (SNPs). Forced-intercalation peptide nucleic acids (FIT-PNAs) are DNA mimics that are designed as RNA-sensing molecules that fluoresce upon hybridization to their complementary (RNA) targets. We have previously designed and synthesized FIT-PNAs that target the C580Y SNP in the K13 gene of P. falciparum. In addition, we have now prepared FIT-PNAs that target the K76T SNP in the CRT gene of P. falciparum. Both SNPs are common ones associated with artemisinin and chloroquine drug resistance, respectively. Our FIT-PNAs are conjugated to a simple cell-penetrating peptide (CPP) that consists of eight d-lysines (dK₈), which renders these FIT-PNAs cell-permeable to infected red blood cells (iRBCs). Herein, we demonstrate that FIT-PNAs clearly discriminate between wild-type (WT) strains (NF54-WT: artemisinin-sensitive or chloroquine-sensitive) and mutant strains (NF54-C580Y: artemisinin-resistant or Dd2: chloroquine-resistant) of P. falciparum parasites. Simple incubation of FIT-PNAs with live blood-stage parasites results in a substantial difference in fluorescence as corroborated by FACS analysis and confocal microscopy. We foresee FIT-PNAs as molecular probes that will provide a fast, simple, and cheap means for the assessment of drug resistance in malaria─a tool that would be highly desirable for the optimal choice of antimalarial treatment in endemic countries.

Cyclopentane FIT-PNAs: bright RNA sensors

Cyclopentane modified FIT-PNA (cpFIT-PNA) probes are reported as highly emissive RNA sensors with the highest reported brightness for FIT-PNAs. Compared to FIT-PNAs, cpFIT-PNAs have improved mismatch discrimination for several pyrimidine-pyrimidine single nucleotide variants (SNVs).

AntimiR-155 Cyclic Peptide-PNA Conjugate: Synthesis, Cellular Uptake, and Biological Activity

Efficient delivery of nucleic acids into cells still remains a great challenge. Peptide nucleic acids (PNAs) are DNA analogues with a neutral backbone and are synthesized by solid phase peptide chemistry. This allows a straightforward synthetic route to introduce a linear short peptide (a.k.a. cell-penetrating peptide) to the PNA molecule as a means of facilitating cellular uptake of PNAs. Herein, we have devised a synthetic route in which a cyclic peptide is prepared on a solid support and is extended with the PNA molecule, where all syntheses are accomplished on the solid phase. This allows the conjugation of the cyclic peptide to the PNA molecule with the need of only one purification step after the cyclic peptide-PNA conjugate (C₉-PNA) is cleaved from the solid support. The PNA sequence chosen is an antimiR-155 molecule that is complementary to mature miR-155, a well-established oncogenic miRNA. By labeling C₉-PNA with fluorescein isothiocyanate, we observe efficient cellular uptake into glioblastoma cells (U87MG) at a low concentration (0.5 μM), as corroborated by fluorescence-activated cell sorting (FACS) analysis and confocal microscopy. FACS analysis also suggests an uptake mechanism that is energy-dependent. Finally, the antimiR activity of C₉-PNA was shown by analyzing miR155 levels by quantitative reverse transcription polymerase chain reaction and by observing a reduction in cell viability and proliferation in U87MG cells, as corroborated by XTT and colony formation assays. Given the added biological stability of cyclic versus linear peptides, this synthetic approach may be a useful and straightforward approach to synthesize cyclic peptide-PNA conjugates.

Modulation of MKNK2 alternative splicing by splice-switching oligonucleotides as a novel approach for glioblastoma treatment

The gene encoding the kinase Mnk2 (MKNK2) is alternatively spliced to produce two isoforms-Mnk2a and Mnk2b. We previously showed that Mnk2a is downregulated in several types of cancer and acts as a tumor suppressor by activation of the p38-MAPK stress pathway, inducing apoptosis. Moreover, Mnk2a overexpression suppressed Ras-induced transformation in culture and in vivo. In contrast, the Mnk2b isoform acts as a pro-oncogenic factor. In this study, we designed modified-RNA antisense oligonucleotides and screened for those that specifically induce a strong switch in alternative splicing of the MKNK2 gene (splice switching oligonucleotides or SSOs), elevating the tumor suppressive isoform Mnk2a at the expense of the pro-oncogenic isoform Mnk2b. Induction of Mnk2a by SSOs in glioblastoma cells activated the p38-MAPK pathway, inhibited the oncogenic properties of the cells, re-sensitized the cells to chemotherapy and inhibited glioblastoma development in vivo. Moreover, inhibition of p38-MAPK partially rescued glioblastoma cells suggesting that most of the anti-oncogenic activity of the SSO is mediated by activation of this pathway. These results suggest that manipulation of MKNK2 alternative splicing by SSOs is a novel approach to inhibit glioblastoma tumorigenesis.

MiR-16-1-3p and miR-16-2-3p possess strong tumor suppressive and antimetastatic properties in osteosarcoma

Osteosarcoma (OS) is an aggressive malignancy affecting mostly children and adolescents. MicroRNAs (miRNAs) play important roles in OS development and progression. Here we found that miR-16-1-3p and miR-16-2-3p "passenger" strands, as well as the "lead" miR-16-5p strand, are frequently downregulated and possess strong tumor suppressive functions in human OS. Furthermore, we report different although strongly overlapping functions for miR-16-1-3p and miR-16-2-3p in OS cells. Ectopic expression of these miRNAs affected primary tumor growth, metastasis seeding and chemoresistance and invasiveness of human OS cells. Loss-of-function experiments verified tumor suppressive functions of these miRNAs at endogenous levels of expression. Using RNA immunoprecipitation (RIP) assays, we identify direct targets of miR-16-1-3p and miR-16-2-3p in OS cells. Moreover, validation experiments identified FGFR2 as a direct target for miR-16-1-3p and miR-16-2-3p. Overall, our findings underscore the importance of passenger strand miRNAs, at least some, in osteosarcomagenesis.

Red-emitting FIT-PNAs: "On site" detection of RNA biomarkers in fresh human cancer tissues

To date, there are limited approaches for the direct and rapid visualization (on site) of tumor tissues for pathological assessment and for aiding cytoreductive surgery. Herein, we have designed FIT-PNAs (forced-intercalation-peptide nucleic acids) to detect two RNA cancer biomarkers. Firstly, a lncRNA (long noncoding RNA) termed CCAT1, has been shown as an oncogenic lncRNA over-expressed in a variety of cancers. The latter, an mRNA termed KRT20, has been shown to be over-expressed in metastases originating from colorectal cancer (CRC). To these FIT-PNAs, we have introduced the bis-quinoline (BisQ) cyanine dye that emits light in the red region (605-610 nm) of the visible spectrum. Most strikingly, spraying fresh human tissue taken from patients during cytoreductive surgery for peritoneal metastasis of colon cancer with an aqueous solution of CCAT1 FIT-PNA results in bright fluorescence in a matter of minutes. In fresh healthy tissue (from bariatric surgeries), no appreciable fluorescence is detected. In addition, a non-targeted FIT-PNA shows no fluorescent signal after spraying this FIT-PNA on fresh tumor tissue emphasizing the specificity of these molecular sensors. This study is the first to show on-site direct and immediate visualization of an RNA cancer biomarker on fresh human cancer tissues by topical application (spraying) of a molecular sensor.

Specific inhibition of splicing factor activity by decoy RNA oligonucleotides

Alternative splicing, a fundamental step in gene expression, is deregulated in many diseases. Splicing factors (SFs), which regulate this process, are up- or down regulated or mutated in several diseases including cancer. To date, there are no inhibitors that directly inhibit the activity of SFs. We designed decoy oligonucleotides, composed of several repeats of a RNA motif, which is recognized by a single SF. Here we show that decoy oligonucleotides targeting splicing factors RBFOX1/2, SRSF1 and PTBP1, can specifically bind to their respective SFs and inhibit their splicing and biological activities both in vitro and in vivo. These decoy oligonucleotides present an approach to specifically downregulate SF activity in conditions where SFs are either up-regulated or hyperactive.

Alternative splicing, critical for gene expression, is deregulated in many diseases. Here the authors develop decoy oligonucleotides to specifically downregulate splicing factors activity.

Protein Regulation by Intrinsically Disordered Regions: A Role for Subdomains in the IDR of the HIV-1 Rev Protein

Intrinsically disordered regions (IDRs) in proteins are highly abundant, but they are still commonly viewed as long stretches of polar, solvent-accessible residues. Here we show that the disordered C-terminal domain (CTD) of HIV-1 Rev has two subregions that carry out two distinct complementary roles of regulating protein oligomerization and contributing to stability. We propose that this takes place through a delicate balance between charged and hydrophobic residues within the IDR. This means that mutations in this region, as well as the known mutations in the structured region of the protein, can affect protein function. We suggest that IDRs in proteins should be divided into subdomains similarly to structured regions, rather than being viewed as long flexible stretches.

Reverting the molecular fingerprint of tumor dormancy as a therapeutic strategy for glioblastoma

Glioblastoma is an aggressive and invasive brain malignancy with high mortality rates despite current treatment modalities. In this study, we show that a 7-gene signature, previously found to govern the switch of glioblastomas from dormancy to aggressive tumor growth, correlates with improved overall survival of patients with glioblastoma. Using glioblastoma dormancy models, we validated the role of 2 genes from the signature, thrombospondin-1 ( TSP-1) and epidermal growth factor receptor ( EGFR), as regulators of glioblastoma dormancy and explored their therapeutic potential. EGFR up-regulation was reversed using EGFR small interfering RNA polyplex, antibody, or small-molecule inhibitor. The diminished function of TSP-1 was augmented via a peptidomimetic. The combination of EGFR inhibition and TSP-1 restoration led to enhanced therapeutic efficacy in vitro, in 3-dimensional patient-derived spheroids, and in a subcutaneous human glioblastoma model in vivo. Systemic administration of the combination therapy to mice bearing intracranial murine glioblastoma resulted in marginal therapeutic outcomes, probably due to brain delivery challenges, p53 mutation status, and the aggressive nature of the selected cell line. Nevertheless, this study provides a proof of concept for exploiting regulators of tumor dormancy for glioblastoma therapy. This therapeutic strategy can be exploited for future investigations using a variety of therapeutic entities that manipulate the expression of dormancy-associated genes in glioblastoma as well as in other cancer types.-Tiram, G., Ferber, S., Ofek, P., Eldar-Boock, A., Ben-Shushan, D., Yeini, E., Krivitsky, A., Blatt, R., Almog, N., Henkin, J., Amsalem, O., Yavin, E., Cohen, G., Lazarovici, P., Lee, J. S., Ruppin, E., Milyavsky, M., Grossman, R., Ram, Z., Calderón, M., Haag, R., Satchi-Fainaro, R. Reverting the molecular fingerprint of tumor dormancy as a therapeutic strategy for glioblastoma.

Predictive Model for the Sequence-Dependent Fluorogenic Response of Forced-Intercalation Peptide Nucleic Acid

The forced-intercalation peptide nucleic acid (FIT-PNA) concept, introduced by Seitz and co-workers, is based on replacing a nucleobase of the PNA sequence with a cyanine dye (such as thiazole orange). The cyanine dye is thus a surrogate base that is forced to intercalate in the duplex (e.g.

, PNA

DNA). This allows single-mismatch sensitivity as the introduction of a mismatch in the vicinity of the dye increases freedom of motion and leads to a significant depletion of its fluorescence because of the free rotation of the monomethine bond separating the two π-systems of the cyanine dye. Herein, we designed and synthesized six FIT-PNA probes, featuring bisquinoline (BisQ), a red-emitting cyanine dye recently developed in our laboratory for FIT-PNAs. By following PNA-DNA duplex fluorescence, we found new sequence-based factors governing the fluorescence response to the mismatched FIT-PNA:DNA duplex. Fluorogenic properties are correlated with the π-stacking energy of three distinctive base pair steps (BPSs) in the PNA:DNA duplex. The first two are the two BPSs opposite BisQ, whereas the third is the BPS of the mismatch position, which presumably becomes unstacked due to the mismatch. We suggest a predictive model for FIT-PNA single-mismatch detection mechanism, a model that can be used in future research to improve FIT-PNA design.

CLIP6-PNA-Peptide Conjugates: Non-Endosomal Delivery of Splice Switching Oligonucleotides

Efficient delivery of oligonucleotides still remains a challenge in the field of oligonucleotide based therapy. Peptide nucleic acid (PNA), a DNA analogue that is typically synthesized by solid phase peptide chemistry, has been conjugated to a variety of cell penetrating peptides (CPP) as a means of improving its cellular uptake. These CPPs typically deliver their cargoes into cells by an endosomal-dependent mechanism resulting in lower bioavailability of the cargo. Herein, we designed and synthesized PNA-peptide conjugates as splice switching oligonucleotides (SSO) targeting the Mnk2 gene, a therapeutic target in cancer. In humans, the MKNK2 gene, is alternatively spliced, generating isoforms with opposite biological activities: Mnk2a and Mnk2b. It was found that the Mnk2a isoform is down-regulated in breast, lung, brain, and colon tumors and is a tumor suppressor, whereas MnK2b is oncogenic. We have designed and synthesized PNAs that were conjugated to either of the following peptides: a nuclear localization sequence (NLS) or a cytosol localizing internalization peptide (CLIP6). CLIP6-PNA demonstrates effective cellular uptake and exclusively employs a nonendosomal mechanism to cross the cellular membranes of glioblastoma cells (U87). Simple incubation of PNA-peptide conjugates in human glioblastoma cells up-regulates the Mnk2a isoform leading to cancer cell death.

Single point mutation detection in living cancer cells by far-red emitting PNA-FIT probes

Peptide nucleic acid bis-quinoline conjugates are reported as attractive far-red emitting probes that detect mutated mRNA in living cells at SNP resolution.

Solid nano-in-nanoparticles for potential delivery of siRNA

siRNA-based therapeutics possess great potential to treat a wide variety of genetic disorders. However, they suffer from low cellular uptake and short half-lives in blood circulation; issues that remain to be addressed. This work is, to the best of our knowledge, the first to report the production of solid nano-in-nanoparticles, termed double nano carriers (DNCs) by means of the innovative technology of nano spray drying. DNCs (with a median size of 580-770nm) were produced by spraying at low temperatures (50°C) to prevent damage to heat-sensitive biomacromolecules like siRNA. DNCs consisting of Poly (d,l-lactide-co-glycolide) used as a wall material, encapsulating 20% human serum albumin primary nanoparticles (PNPs) loaded with siRNA, were obtained as a dry nanoparticulate powder with smooth spherical surfaces and a unique inner morphology. Incubation of pegylated or non-pegylated DNCs under sink conditions at 37°C, elicited a controlled release profile of the siRNA for up to 12 or 24h, respectively, with a minimal burst effect. Prolonged incubation of pegylated DNCs loaded with active siRNA (anti EGFR) in an A549 epithelial cell culture monolayer did not induce any apparent cytotoxicity. A slow degradation of the internalized DNCs by the cells was also observed resulting in the progressive release of the siRNA for up to 6days, as corroborated by laser confocal microscopy. The structural integrity and silencing activity of the double encapsulated siRNA were fully preserved, as demonstrated by HPLC, gel electrophoresis, and potent RNAi activity of siRNA extracted from DNCs. These results demonstrate the potential use of DNCs as a nano drug delivery system for systemic administration and controlled release of siRNA and potentially other sensitive bioactive macromolecules.

Postsynthetic conjugation of RNA to carboxylate and dicarboxylate molecules

Carboxylates and dicarboxylates are important phosphate mimics. Herein, we present a simple synthetic route for the preparation of RNA carboxylate/dicarboxylate conjugates, starting from suitably protected NH2- and COOH-containing molecules that are coupled to the RNA on the solid support. The key point in our method was the use of trimethylsilylethanol (TMSE-OH) protecting group, which is removed simultaneously with the silyl protecting group on the 2'-OH of the RNA ribose (e.g. t-Butyldimethylsilyl) during the final RNA cleavage/deprotection steps. The usefulness of this method was demonstrated by preparing different RNA-phosphate mimics oligos.

PNA-Rose Bengal Conjugates as Efficient DNA Photomodulators

Selective photoinduced modulation of DNA may provide a powerful therapeutic tool allowing spatial and temporal control of the photochemical reaction. We have explored the photoreactivity of peptide nucleic acid (PNA) conjugates that were conjugated to a highly potent photosensitizer, Rose Bengal (RB). In addition, a short PEGylated peptide (K-PEG8-K) was conjugated to the C-terminus of the PNA to improve its water solubility. A short irradiation (visible light) of PNA conjugates with a synthetic DNA resulted in highly efficient photomodulation of the DNA as evidenced by polyacrylamide gel electrophoresis (PAGE). In addition, a PNA-RB conjugate replacing K-PEG8-K with four l-glutamic acids (E4) was found to be photoinactive. Irradiation of active PNA-RB conjugates with synthetic DNA in D20 augments the photoactivity; supporting the involvement of singlet oxygen. PAGE, HPLC, and MALDI-TOF analyses indicate that PNA-DNA photo-cross-linking is a significant pathway in the observed photoreactivity. Selective photo-cross-linking of such PNA-RB conjugates may be a novel approach to selective photodynamic therapy (sPDT) as such molecules would be sequence-specific, cell-permeable, and photoactivated in the visible region.

On the stability of Pt(IV) pro-drugs with haloacetato ligands in the axial positions

The design of Pt(IV) pro-drugs as anticancer agents is predicated on the assumption that they will not undergo substitution reactions before entering the cancer cell. Attempts to improve the cytotoxic properties of Pt(IV) pro-drugs included the use of haloacetato axial ligands. Herein, we demonstrate that Pt(IV) complexes with trifluoroacetato (TFA) or dichloroacetato (DCA) ligands can be unstable under biologically relevant conditions and readily undergo hydrolysis, which results in the loss of the axial TFA or DCA ligands. The half-lives for Pt(IV) complexes with two TFA or DCA ligands at pH 7 and 37 °C range from 6 to 800 min, which is short relative to the duration of cytotoxicity experiments that last 24-96 h. However, complexes with two monochloroacetato (MCA) or acetato axial ligands are stable under biologically relevant conditions. The loss of the axial ligands depends primarily on the electron-withdrawing strength of the axial ligands, but also upon the nature of the equatorial ligands. We were unable to find obvious correlations between the structures of the Pt(IV) complexes and the rates of decay of the parent compounds. The X-ray crystal structures of the bis-DCA and bis-MCA Pt(IV) derivatives of oxaliplatin did not reveal any significant structural differences that could explain the observed differences in stability.

Abstract LB-104: Reverting the angiogenic switch of glioblastoma with a nanopolyplex based on the molecular fingerprint of tumor dormancy

Small,microscopic, avascular and therefore asymptomatic tumors can remain in their dormant stage for a considerable period of time depending on numerous processes. One crucial mechanism underlying the transformation from a dormant to a fast-growing phenotype is the ability of tumor cells to induce angiogenesis, a phenomenon termed “angiogenic switch”. We used the aggressive tumor-forming U-87 MG human glioblastoma cell line to identify and isolate a clone which generates dormant microscopic tumors (1). This clone was isolated using single-cell clone and identified by gene expression signature of dormant tumors (2). While both cell lines share a similar growth rate in vitro, we found profound differences in tumor growth patterns when injected into mice. Furthermore, both cell lines exhibit major differences in their angiogenic potential and in expression patterns of genes involved in angiogenesis regulation. Two of the major dissimilarities were found in thrombospondin-1 (TSP-1) and epidermal growth factor receptor (EGFR) expression levels. The dormant avascular tumor-generating cell line (U-87-D) expresses significantly higher levels of TSP-1 and lower levels of EGFR compared to the fast-growing angiogenic tumor-generating parental cell line (U-87-F). It has been previously demonstrated that TSP-1 is a key endogenous angiogenesis inhibitor, whose expression is lost during the malignant transformation. EGFR is a major modulator of tumorigenicity in glioblastoma and therefore, is considered an attractive potential target for glioblastoma therapy.

Following the identification of a tumor dormancy gene signature, we induced the upregulation of TSP-1 signaling, using a TSP-1 peptidomimetic (TSP-1 PM), and the downregulation of EGFR, using a dendritic nanocarrier entrapping siRNA (polyglycerol amine (PG-NH2)-siEGFR). We evaluated the ability of this combination therapy to reverse the fast-growing angiogenic phenotype of U-87-F to the dormant avascular phenotype of U-87-D. Mice bearing established U-87-F tumors (50 mm3) received TSP-1 PM (50 mg/kg/day every day) and PG-NH2-siEGFR (2 mg/kg twice a week) for 14 days. This combination therapy exhibited anti-angiogenic and anti-tumorigenic activity. It remarkably decreased tumor volume by 99.5% compared with the control on day 25 post treatment initiation, to a volume of ∼1 mm3.Immunohistochemistry analysis of TSP-1 PM-treated tumors revealed reduced abnormal vasculature, increased αSMA expression and decreased VEGF expression. We concluded that TSP-1 PM in combination with EGFR-siRNA present a promising treatment for advanced glioblastoma promoting a dormant phenotype.

References:

1. Satchi-Fainaro*, Ferber*, et al., Prospective Identification of Glioblastoma Cells Generating Dormant Tumors, in press, PLoS One (2012). * Equal contribution.

2. Almog et al., Transcriptional switch of dormant tumors to fast-growing angiogenic phenotype Cancer Res. 2009; 69(3):836-44.

Citation Format: Shiran Ferber, Galia Tiram, Orit Amsalem, Eylon Yavin, Nava Almog, Jack Henkin, Marcelo Calderon, Rainer Haag, Ronit Satchi-Fainaro. Reverting the angiogenic switch of glioblastoma with a nanopolyplex based on the molecular fingerprint of tumor dormancy. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr LB-104. doi:10.1158/1538-7445.AM2014-LB-104

Synthesis and evaluation of a photoresponsive quencher for fluorescent hybridization probes

Nowadays, most nucleic acid detections using fluorescent probes rely on quenching of fluorescence by energy transfer from one fluorophore to another or to a non-fluorescent molecule (quencher). The most widely used quencher in fluorescent probes is 4-((4-(dimethylamino)phenyl)azo)benzoic acid (DABCYL). We targeted a nucleoside-DABCYL analogue which could be incorporated anywhere in an oligonucleotide sequence and in any number, and used as a quencher in different hybridization sensitive probes. Specifically, we introduced a 5-(4-((dimethylamino)phenyl)azo)benzene)-2'-deoxy-uridine (dU(DAB)) quencher. The photoisomerization and dU(DAB)'s ability to quench fluorescein emission have been investigated. We incorporated dU(DAB) into a series of oligonucleotide (ON) probes including strand displacement probes, labeled with both fluorescein (FAM) and dU(DAB), and TaqMan probes bearing one or two dU(DAB) and a FAM fluorophore. We used these probes for the detection of a DNA target in real-time PCR (RT-PCR). All probes showed amplification of targeted DNA. A dU(DAB) modified TaqMan RT-PCR probe was more efficient as compared to a DABCYL bearing probe (93% vs. 87%, respectively). Furthermore, dU(DAB) had a stabilizing effect on the duplex, causing an increase in Tm up to 11 °C. In addition we showed the photoisomerisation of the azobenzene moiety of dU(DAB) and the dU(DAB) triply-labeled oligonucleotide upon irradiation. These findings suggest that dU(DAB) modified probes are promising probes for gene quantification in real-time PCR detection and as photoswitchable devices.

Detection of cyclin D1 mRNA by hybridization sensitive NIC-oligonucleotide probe

A large group of fluorescent hybridization probes, includes intercalating dyes for example thiazole orange (TO). Usually TO is coupled to nucleic acids post-synthetically which severely limits its use. Here, we have developed a phosphoramidite monomer, 10, and prepared a 2'-OMe-RNA probe, labeled with 5-(trans-N-hexen-1-yl-)-TO-2'-deoxy-uridine nucleoside, dU(TO), (Nucleoside bearing an Inter-Calating moiety, NIC), for selective mRNA detection. We investigated a series of 15-mer 2'-OMe-RNA probes, targeting the cyclin D1 mRNA, containing one or several dU(TO) at various positions. dU(TO)-2'-OMe-RNA exhibited up to 7-fold enhancement of TO emission intensity upon hybridization with the complementary RNA versus that of the oligomer alone. This NIC-probe was applied for the specific detection of a very small amount of a breast cancer marker, cyclin D1 mRNA, in total RNA extract from cancerous cells (250 ng/μl). Furthermore, this NIC-probe was found to be superior to our related NIF (Nucleoside with Intrinsic Fluorescence)-probe which could detect cyclin D1 mRNA target only at high concentrations (1840 ng/μl). Additionally, dU(T) can be used as a monomer in solid-phase oligonucleotide synthesis, thus avoiding the need for post-synthetic modification of oligonucleotide probes. Hence, we propose dU(TO) oligonucleotides, as hybridization probes for the detection of specific RNA in homogeneous solutions and for the diagnosis of breast cancer.

Use of peptide nucleic acids to manipulate gene expression in the malaria parasite Plasmodium falciparum

One of the major concerns in treating malaria by conventional small drug molecules is the rapid emergence of drug resistance. Specific silencing of essential genes by antisense oliogomers has been proposed as an alternative approach that may result in antimalarial activity which is not associated with drug resistance. In addition, such an approach could be an important biological tool for studying many genes' function by reverse genetics. Here we present a novel methodology of using peptide nucleic acids (PNAs) as a useful tool for gene silencing in Plasmodium falciparum. PNAs, designed as specific antisense molecules, were conjugated to a cell penetrating peptide (CPP); namely, octa-D-lysine via the C-terminus, to allow facile delivery through cell membranes. PNAs added to P. falciparum cultures were found exclusively in infected erythrocytes and were eventually localized in nuclei of the parasites at all stages of intra erythrocytic development. We show that these PNAs specifically down regulated both a stably expressed transgene as well as an endogenous essential gene, which significantly reduced parasites' viability. This study paves the way for a simple approach to silence a variety of P. falciparum genes as means of deciphering their function and potentially to develop highly specific and potent antimalarial agents.

Detection of mRNA of the cyclin D1 breast cancer marker by a novel duplex-DNA probe

Previously, we have described 5-((4-methoxy-phenyl)-trans-vinyl)-2'-deoxy-uridine, 6, as a fluorescent uridine analogue exhibiting a 3000-fold higher quantum yield (Φ 0.12) and maximum emission (478 nm) which is 170 nm red-shifted as compared to uridine. Here, we utilized 6 for preparation of labeled oligodeoxynucleotide (ODN) probes based on MS2 and cyclin D1 (a known breast cancer mRNA marker) sequences. Cyclin D1-derived labeled-ssODN showed a 9.5-fold decrease of quantum yield upon duplex formation. On the basis of this finding, we developed the ds-NIF (nucleoside with intrinsic fluorescence)-probe methodology for detection of cyclin D1 mRNA, by which the fluorescent probe is released upon recognition of target mRNA by the relatively dark NIF-duplex-probe. Indeed, we successfully detected, a ss-deoxynucleic acid (DNA) variant of cyclin D1 mRNA using a dark NIF-labeled duplex-probe, and monitoring the recognition process by fluorescence spectroscopy and gel electrophoresis. Furthermore, we successfully detected cyclin D1 mRNA in RNA extracted from cancerous human cells, using ds-NIF methodology.

Platinum(IV) prodrugs with haloacetato ligands in the axial positions can undergo hydrolysis under biologically relevant conditions

Losing ligands rapidly: Pt(IV) complexes with haloacetato ligands can hydrolyze rapidly under biological conditions (pH 7 and 37 °C, see scheme) and the rate increases with increasing pH value. Possible mechanisms for this hydrolysis are examined using H2(18)O and ESI-MS analysis.

PfSec13 is an unusual chromatin-associated nucleoporin of Plasmodium falciparum that is essential for parasite proliferation in human erythrocytes

In Plasmodium falciparum, the deadliest form of human malaria, the nuclear periphery has drawn much attention due to its role as a sub-nuclear compartment involved in virulence gene expression. Recent data have implicated components of the nuclear envelope in regulating gene expression in several eukaryotes. Special attention has been given to nucleoporins that compose the nuclear pore complex (NPC). However, very little is known about components of the nuclear envelope in Plasmodium parasites. Here we characterize PfSec13, an unusual nucleoporin of P. falciparum, which shows unique structural similarities suggesting that it is a fusion between Sec13 and Nup145C of yeast. Using super resolution fluorescence microscopy (3D-SIM) and in vivo imaging, we show that the dynamic localization of PfSec13 during parasites' intra-erythrocytic development corresponds with that of the NPCs and that these dynamics are associated with microtubules rather than with F-actin. In addition, PfSec13 does not co-localize with the heterochormatin markers HP1 and H3K9me3, suggesting euchromatic location of the NPCs. The proteins associated with PfSec13 indicate that this unusual Nup is involved in several cellular processes. Indeed, ultrastructural and chromatin immunoprecipitation analyses revealed that, in addition to the NPCs, PfSec13 is found in the nucleoplasm where it is associated with chromatin. Finally, we used peptide nucleic acids (PNA) to downregulate PfSec13 and show that it is essential for parasite proliferation in human erythrocytes.

Bio-imaging of colorectal cancer models using near infrared labeled epidermal growth factor

Novel strategies that target the epidermal growth factor receptor (EGFR) have led to the clinical development of monoclonal antibodies, which treat metastatic colorectal cancer (mCRC) but only subgroups of patients with increased wild type KRAS and EGFR gene copy, respond to these agents. Furthermore, resistance to EGFR blockade inevitably occurred, making future therapy difficult. Novel bio-imaging (BOI) methods may assist in quantization of EGFR in mCRC tissue thus complementing the immunohistochemistry methodology, in guiding the future treatment of these patients. The aim of the present study was to explore the usefulness of near infrared-labeled EGF (EGF-NIR) for bio-imaging of CRC using in vitro and in vivo orthotopic tumor CRC models and ex vivo human CRC tissues. We describe the preparation and characterization of EGF-NIR and investigate binding, using BOI of a panel of CRC cell culture models resembling heterogeneity of human CRC tissues. EGF-NIR was specifically and selectively bound by EGFR expressing CRC cells, the intensity of EGF-NIR signal to background ratio (SBR) reflected EGFR levels, dose-response and time course imaging experiments provided optimal conditions for quantization of EGFR levels by BOI. EGF-NIR imaging of mice with HT-29 orthotopic CRC tumor indicated that EGF-NIR is more slowly cleared from the tumor and the highest SBR between tumor and normal adjacent tissue was achieved two days post-injection. Furthermore, images of dissected tissues demonstrated accumulation of EGF-NIR in the tumor and liver. EGF-NIR specifically and strongly labeled EGFR positive human CRC tissues while adjacent CRC tissue and EGFR negative tissues expressed weak NIR signals. This study emphasizes the use of EGF-NIR for preclinical studies. Combined with other methods, EGF-NIR could provide an additional bio-imaging specific tool in the standardization of measurements of EGFR expression in CRC tissues.

Relacin, a novel antibacterial agent targeting the Stringent Response

Finding bacterial cellular targets for developing novel antibiotics has become a major challenge in fighting resistant pathogenic bacteria. We present a novel compound, Relacin, designed to inhibit (p)ppGpp production by the ubiquitous bacterial enzyme RelA that triggers the Stringent Response. Relacin inhibits RelA in vitro and reduces (p)ppGpp production in vivo. Moreover, Relacin affects entry into stationary phase in Gram positive bacteria, leading to a dramatic reduction in cell viability. When Relacin is added to sporulating Bacillus subtilis cells, it strongly perturbs spore formation regardless of the time of addition. Spore formation is also impeded in the pathogenic bacterium Bacillus anthracis that causes the acute anthrax disease. Finally, the formation of multicellular biofilms is markedly disrupted by Relacin. Thus, we establish that Relacin, a novel ppGpp analogue, interferes with bacterial long term survival strategies, placing it as an attractive new antibacterial agent.

The development of new antibacterial agents has become the major demand for fighting against pathogenic bacteria. The identification of new unexplored cellular targets in this combat is essential to prevent a possible return to the pre-antibiotic era. Traditional antibiotics target essential cellular components such as ribosomes and cell wall constituents, making them effective mostly during bacterial growth. However, the ability of bacteria to reside in nature at durable stages sets the need to cope with these alternative survival strategies. In this report, we present a novel antibiotic, termed Relacin, which targets the Stringent Response, a process required for the transition into stationary phase, crucial for bacterial survival. Relacin inhibits the abundant bacterial Rel enzymes that synthesize the signaling molecules required to activate the Stringent Response. We found that Relacin perturbs the switch into stationary phase in Gram positive bacteria and leads to cell death. Further, Relacin inhibits sporulation and biofilm formation, additional bacterial long term survival strategies. The ubiquity of Rel enzymes among bacteria, combined with the absence of known homologues in mammalian cells, strengthen the potential of Relacin to turn into a therapeutic antibiotic.

Detection of endogenous K-ras mRNA in living cells at a single base resolution by a PNA molecular beacon

Detection of mRNA alterations is a promising approach for identifying biomarkers as means of differentiating benign from malignant lesions. By choosing the KRAS oncogene as a target gene, two types of molecular beacons (MBs) based on either phosphothioated DNA (PS-DNA-MB) or peptide nucleic acid (TO-PNA-MB, where TO = thiazole orange) were synthesized and compared in vitro and in vivo. Their specificity was examined in wild-type KRAS (HT29) or codon 12 point mutation (Panc-1, SW480) cells. Incubation of both beacons with total RNA extracted from the Panc-1 cell line (fully complementary sequence) showed a fluorescent signal for both beacons. Major differences were observed, however, for single mismatch mRNA transcripts in cell lines HT29 and SW480. PS-DNA-MB weakly discriminated such single mismatches in comparison to TO-PNA-MB, which was profoundly more sensitive. Cell transfection of TO-PNA-MB with the aid of PEI resulted in fluorescence in cells expressing the fully complementary RNA transcript (Panc-1) but undetectable fluorescence in cells expressing the K-ras mRNA that has a single mismatch to the designed TO-PNA-MB (HT29). A weaker fluorescent signal was also detected in SW480 cells; however, these cells express approximately one-fifth of the target mRNA of the designed TO-PNA-MB. In contrast, PS-DNA-MB showed no fluorescence in all cell lines tested post PEI transfection. Based on the fast hybridization kinetics and on the single mismatch discrimination found for TO-PNA-MB we believe that such molecular beacons are promising for in vivo real-time imaging of endogenous mRNA with single nucleotide polymorphism (SNP) resolution.

c-di-AMP reports DNA integrity during sporulation in Bacillus subtilis

The bacterium Bacillus subtilis produces the DNA integrity scanning protein (DisA), a checkpoint protein that delays sporulation in response to DNA damage. DisA scans the chromosome and pauses at sites of DNA lesions. Structural analysis showed that DisA synthesizes the small molecule cyclic diadenosine monophosphate (c-di-AMP). Here, we demonstrate that the intracellular concentration of c-di-AMP rises markedly at the onset of sporulation in a DisA-dependent manner. Furthermore, exposing sporulating cells to DNA-damaging agents leads to a global decrease in the level of this molecule. This drop was associated with stalled DisA complexes that halt c-di-AMP production and with increased levels of the c-di-AMP-degrading enzyme YybT. Reduced c-di-AMP levels cause a delay in sporulation that can be reversed by external supplementation of the molecule. Thus, c-di-AMP acts as a secondary messenger, coupling DNA integrity with progression of sporulation.

Abstract 3062: A comparative analysis of phosphothioated DNA and peptide nucleic acid molecular beacons targeting specific K-ras mutation

Introduction: Early detection of gastrointestinal malignancies may improve disease-related outcome. In vivo, real time imaging using hybridization of fluorescently-labeled complementary transcripts to intracellular RNA sequences may facilitate early detection of malignant and pre-malignant lesions

Methods: Using K-ras oncogene as a model target, and adapting the molecular beacon technology, we performed an hybridization kinetics and hybridization specificity comparison of two types of molecular beacons (MBs) based on either phosphothioated DNA (PS-DNA-MB) or peptide nucleic acid (PNA-TO-MB, where thiazole orange [TO] was used as the fluorescent molecule) both in vitro and in a variety of cell lines. In order to determine the sequence-specificity of MB's at a single base resolution, a codon 12 K-ras oncogene mutation (GGT→GAT) was used as target in different cell lines. Both PS-DNA and PNA-TO MB's were designed to target this specific K-ras point mutation. We studied the hybridization of the two MBs to wild-type K-ras (HT-29 colon cancer cell line) and two cell lines, one harboring this K-ras point mutation (PANC-1) and SW-480 harboring a different (GGT→GTT) mutation.

Results: Hybridization kinetics of PNA-TO-MB to target DNA or RNA was faster compared to PS-DNA-MB highlighting the advantage of such probes to be developed into diagnostic kits for the early detection of cancer. However, in solution, using synthetic DNA oligomers as targets, PS-DNA-MB demonstrated higher specificity to its complementary target (3-to 4.6-fold increase in fluorescence in comparison to DNA with a single mismatch) compared to the PNA-TO-MB (only 1.3- to 2.2-fold increase). Yet, incubation of PNA-TO-MB with total RNA (isolated from these cell lines) and with fixed cells, resulted in a significantly higher fluorescent signal (p < 0.001) detected for target (fully complement, PANC-1) compared to single mismatch mRNA transcript in HT29 and SW-480. In contrast, the PS-DNA-MB showed poor discrimination in total RNA and no fluorescent signal with all cell lines after 5 minutes incubation.

Conclusions: Based on the fast hybridization kinetics and based on the single mismatch discrimination found for PNA-TO-MB in fixed cells and with total RNA, it is speculated that such PNA-TO-MB's are promising candidates for the early detection of cancer.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3062. doi:10.1158/1538-7445.AM2011-3062

Specific detection of gastric alpha-antitrypsin by immobilized trypsin on polyHEMA films

Early diagnosis of gastric carcinoma is crucial for maximizing medical treatment efficacy. For the purpose of real time diagnosis ("virtual biopsy") of stomach malignancy we developed a polyHEMA platform capable of capturing human alpha1-antitrypsin precursor (A1AT); a model proteinaceous luminal biomarker. Its specific attachment to the polymeric platform was accomplished by immobilized trypsin, which was linked to the surface of the polyHEMA film by a series of PEG-based spacers. Recognition was enabled by adapting an ELISA-like methodology, using rabbit anti-A1AT and HRP-conjugated anti-rabbit IgG as a secondary antibody. Since this A1AT-sensing platform was designed to be detected by endoscopic means such as a video capsule, its physical stability was tested after casting on top of a polycarbonate surface. It was found that, in contrast to classical ELISA analysis performed on polystyrene plates, A1AT detection was possible only when spacer arms were used to immobilize the capturing moiety, trypsin, with a 7-fold increase in the optical signal and a saturation kinetics dependency upon the concentration of the A1AT biomarker.

DNA photocleavage by DNA and DNA-LNA amino acid-dye conjugates

DNA photocleavage by triplex forming oligonucleotides (TFO) has potential implications in both biotechnology and medicine. We have synthesized a series of homopurine DNA and DNA/LNA 14-mers to which an amino acid (glycine or l-tryptophan) and a cyanine dye are covalently linked. Two cyanine dyes were examined that include a quinolinium ring linked to a benzothiazolium ring through a monomethine (TO1) or trimethine (TO2) linker. The 14-mer sequence was chosen to target mdm2, a ubiquitin ligase (E3) that regulates p53 by promoting its ubiquitylation and proteosomal degradation. Such inhibition has been previously proposed as a therapeutic approach to target wild-type p53-expressing cancers. To examine whether our TFO conjugates photocleave the mdm2 target, we incubated the various conjugates with the mdm2 plasmid and irradiated the samples with visible light. We show that only the TFO with the complementary sequence and with an intervening l-tryptophan leads to the linearization of the plasmid after a short irradiation time (10 min) exciting the dye (lambda(max)(TO1) = 500 nm and lambda(max)(TO2) = 630 nm) with visible light. Furthermore, the photoreactivity is more pronounced for the LNA/DNA conjugate, an observation that is consistent with improved hybridization to the DNA target. Sequence specificity of the photoreaction is further corroborated on a synthetic 44-mer duplex containing the TFO site. Evidence for a ROS-dependent mechanism is also given and discussed.

Coupling into the Base Pair Stack Is Necessary for DNA-Mediated Electrochemistry

The electrochemistry of DNA films modified with different redox probes linked to DNA through saturated and conjugated tethers was investigated. Experiments feature two redox probes bound to DNA on two surfaces: anthraquinone (AQ)-modified uridines incorporated into thiolated DNA on gold (Au) and 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO)-modified uridines in pyrene-labeled DNA on highly oriented pyrolytic graphite (HOPG). The electrochemistry of these labels when incorporated into DNA has been examined in DNA films containing both well matched and mismatched DNA. DNA-mediated electrochemistry is found to be effective for the TEMPO probe linked with an acetylene linker but not for a saturated TEMPO connected through an ethylenediamine linker. For the AQ probe, DNA-mediated electrochemistry is found with an acetylene linker to uridine but not with an alkyl chain to the 5' terminus of the oligonucleotide. Large electrochemical signals and effective discrimination of intervening base mismatches are achieved for the probes connected through the acetylene linkages, while probes connected through saturated linkages exhibit small electrochemical signals associated only with direct surface to probe charge transfer and poor mismatch discrimination. Thus DNA electrochemistry with these probes is dramatically influenced by the chemical nature of their linkage to DNA. These results highlight the importance of effective coupling into the pi-stack for long-range DNA-mediated electrochemistry.

DNA repair glycosylases with a [4Fe-4S] cluster: a redox cofactor for DNA-mediated charge transport?

The [4Fe-4S] cluster is ubiquitous to a class of base excision repair enzymes in organisms ranging from bacteria to man and was first considered as a structural element, owing to its redox stability under physiological conditions. When studied bound to DNA, two of these repair proteins (MutY and Endonuclease III from Escherichia coli) display DNA-dependent reversible electron transfer with characteristics typical of high potential iron proteins. These results have inspired a reexamination of the role of the [4Fe-4S] cluster in this class of enzymes. Might the [4Fe-4S] cluster be used as a redox cofactor to search for damaged sites using DNA-mediated charge transport, a process well known to be highly sensitive to lesions and mismatched bases? Described here are experiments demonstrating the utility of DNA-mediated charge transport in characterizing these DNA-binding metalloproteins, as well as efforts to elucidate this new function for DNA as an electronic signaling medium among the proteins.

Electron trap for DNA-bound repair enzymes: a strategy for DNA-mediated signaling

Despite a low copy number within the cell, base excision repair (BER) enzymes readily detect DNA base lesions and mismatches. These enzymes also contain [Fe4S4] clusters, yet a redox role for these iron cofactors had been unclear. Here, we provide evidence that BER proteins may use DNA-mediated redox chemistry as part of a signaling mechanism to detect base lesions. By using chemically modified bases, we show electron trapping on DNA in solution with bound BER enzymes by electron paramagnetic resonance (EPR) spectroscopy. We demonstrate electron transfer from two BER proteins, Endonuclease III (EndoIII) and MutY, to modified bases in DNA containing oxidized nitroxyl radical EPR probes. Electron trapping requires that the modified base is coupled to the DNA pi-stack, and trapping efficiency is increased when a noncleavable MutY substrate analogue is located distally to the trap. These results are consistent with DNA binding leading to the activation of the repair proteins toward oxidation. Significantly, these results support a mechanism for DNA repair that involves DNA-mediated charge transport.

Overexpression of dopamine receptor genes and their products in the postnatal rat brain following maternal n-3 fatty acid dietary deficiency

A combination of PCR-Select cDNA subtraction and gene array hybridization was used to identify differentially expressed genomic markers in brains of rats fed for 3 weeks in utero and 2 weeks after birth on an n-3 polyunsaturated fatty acid (PUFA)-deficient diet supplied to dams. Total RNA was isolated, switch mechanism at 5'-end of the RNA transcripts (SMART) applied and used for PCR-Select subtraction of PUFA-deficient and adequately-fed control preparations. Subtracted and amplified ds-cDNA end-products were fragmented, terminally labeled with biotin-ddUTP and hybridized with a RN-U34A gene array. A 10-fold increase in potential genes with log2(Tester/Driver) = 1.4 was found compared with traditional gene array technology when the same chip was tested using non-subtracted targets. Reverse transcription-real-time relative PCR confirmed 30% of the transcripts. Among the validated transcripts, D1 and D2 receptors for dopamine (DA), were most prominent among a number of over-expressed neurotransmitter receptors and retinoic acid receptor (RXR alpha-2 and alpha-1). Immunohistochemical staining of brain sections from 2-week-old pups revealed a substantial enrichment of the D2 receptor in discrete regions of the mesolimbic and mesocortical pathways as well as in a large number of brain areas from the n-3 PUFA-deficient pups. Punches of the same areas run on western blots showed similar results. The overwhelming expression of D1 and D2 receptors may be attributed to a behavioral hypersensitivity caused by the possible impairment of DA production during brain development, which may have implications in certain disorders of the nervous system.

DNA-bound redox activity of DNA repair glycosylases containing [4Fe-4S] clusters

MutY and endonuclease III, two DNA glycosylases from Escherichia coli, and AfUDG, a uracil DNA glycosylase from Archeoglobus fulgidus, are all base excision repair enzymes that contain the [4Fe-4S](2+) cofactor. Here we demonstrate that, when bound to DNA, these repair enzymes become redox-active; binding to DNA shifts the redox potential of the [4Fe-4S](3+/2+) couple to the range characteristic of high-potential iron proteins and activates the proteins toward oxidation. Electrochemistry on DNA-modified electrodes reveals potentials for Endo III and AfUDG of 58 and 95 mV versus NHE, respectively, comparable to 90 mV for MutY bound to DNA. In the absence of DNA modification of the electrode, no redox activity can be detected, and on electrodes modified with DNA containing an abasic site, the redox signals are dramatically attenuated; these observations show that the DNA base pair stack mediates electron transfer to the protein, and the potentials determined are for the DNA-bound protein. In EPR experiments at 10 K, redox activation upon DNA binding is also evident to yield the oxidized [4Fe-4S](3+) cluster and the partially degraded [3Fe-4S](1+) cluster. EPR signals at g = 2.02 and 1.99 for MutY and g = 2.03 and 2.01 for Endo III are seen upon oxidation of these proteins by Co(phen)(3)(3+) in the presence of DNA and are characteristic of [3Fe-4S](1+) clusters, while oxidation of AfUDG bound to DNA yields EPR signals at g = 2.13, 2.04, and 2.02, indicative of both [4Fe-4S](3+) and [3Fe-4S](1+) clusters. On the basis of this DNA-dependent redox activity, we propose a model for the rapid detection of DNA lesions using DNA-mediated electron transfer among these repair enzymes; redox activation upon DNA binding and charge transfer through well-matched DNA to an alternate bound repair protein can lead to the rapid redistribution of proteins onto genome sites in the vicinity of DNA lesions. This redox activation furthermore establishes a functional role for the ubiquitous [4Fe-4S] clusters in DNA repair enzymes that involves redox chemistry and provides a means to consider DNA-mediated signaling within the cell.

Synthesis and biological evaluation of lipophilic iron chelators as protective agents from oxidative stress

Lipophilic Fe(III) chelators were synthesized and shown to protect oligodendrial cells from oxidative damage induced by Fe(III) and hydrogen peroxide.