3-cyanovinylcarbazole Nucleoside Research Articles

Mutation enrichment in human DNA samples via UV-mediated cross-linking.

Detection of low-level DNA mutations can reveal recurrent, hotspot genetic changes of clinical relevance to cancer, prenatal diagnostics, organ transplantation or infectious diseases. However, the high excess of wild-type (WT) alleles, which are concurrently present, often hinders identification of salient genetic changes. Here, we introduce UV-mediated cross-linking minor allele enrichment (UVME), a novel approach that incorporates ultraviolet irradiation (∼365 nm UV) DNA cross-linking either before or during PCR amplification. Oligonucleotide probes matching the WT target sequence and incorporating a UV-sensitive 3-cyanovinylcarbazole nucleoside modification are employed for cross-linking WT DNA. Mismatches formed with mutated alleles reduce DNA binding and UV-mediated cross-linking and favor mutated DNA amplification. UV can be applied before PCR and/or at any stage during PCR to selectively block WT DNA amplification and enable identification of traces of mutated alleles. This enables a single-tube PCR reaction directly from genomic DNA combining optimal pre-amplification of mutated alleles, which then switches to UV-mediated mutation enrichment-based DNA target amplification. UVME cross-linking enables enrichment of mutated KRAS and p53 alleles, which can be screened directly via Sanger sequencing, high-resolution melting, TaqMan genotyping or digital PCR, resulting in the detection of mutation allelic frequencies of 0.001–0.1% depending on the endpoint detection method. UV-mediated mutation enrichment provides new potential for mutation enrichment in diverse clinical samples.

Single-Molecule Imaging and Labelling with DNA-Based Superresolution Microscopy

Recent advances in localisation-based super-resolution microscopy have enabled researchers to visualise single molecular features down to individual molecular components (∼5 nm), but do not yet allow manipulation of single-molecule targets in a user-prescribed, context-dependent manner. Here we report an “Action-PAINT” strategy for super-resolution labelling upon visualisation on single molecules. This approach monitors and localises DNA binding events in real-time with DNA-PAINT, and upon visualisation of binding to a desired location, photo-crosslinks the DNA to affix the molecular label. We showed the efficiency of 3-cyanovinylcarbazole nucleoside (CNVK) photo-inducible crosslinking on single molecular targets and developed a software package for real-time super-resolution imaging and crosslinking control. We then benchmarked our super-resolution labelling method on synthetic DNA nanostructures and demonstrated targeted multi-point labelling on various complex patterns with 30 nm selectivity. Finally, we performed targeted in situ labelling on fixed microtubule samples with 40 nm target size and custom-controlled, sub-diffraction spacing.

Super-resolution labelling with Action-PAINT.

Recent advances in localisation-based super-resolution microscopy have enabled researchers to visualise single molecular features down to individual molecular components (~5 nm), but do not yet allow manipulation of single-molecule targets in a user-prescribed, context-dependent manner. Here we report an “Action-PAINT” strategy for super-resolution labelling upon visualisation on single molecules. This approach monitors and localises DNA binding events in real-time with DNA-PAINT, and upon visualisation of binding to a desired location, photo-crosslinks the DNA to affix the molecular label. We showed the efficiency of 3-cyanovinylcarbazole nucleoside (CNVK) photo-inducible crosslinking on single molecular targets and developed a software package for real-time super-resolution imaging and crosslinking control. We then benchmarked our super-resolution labelling method on synthetic DNA nanostructures and demonstrated targeted multi-point labelling on various complex patterns with 30 nm selectivity. Finally, we performed targeted in situ labelling on fixed microtubule samples with 40 nm target size and custom-controlled, sub-diffraction spacing.

Strong Inhibitory Effects of Antisense Probes on Gene Expression through Ultrafast RNA Photocrosslinking.

We have reported the photochemical regulation of the intracellular antisense effect of antisense probes containing a photo-responsive artificial nucleic acid, 3-cyanovinylcarbazole nucleoside (CNV K). Here we focus on the importance of the photocrosslinking rate on the inhibitory effect on gene expression using photocrosslinkable antisense probes (pcASOs). The inhibitory effect of pcASOs on GFP gene expression was dependent on the photocrosslinking rate of 3-cyanovinylcarbazole with d-threoninol (CNV D), CNV K, or psoralen. The ultrafast RNA photocrosslinking induced the formation of a thermally irreversible covalent bond between pcASOs and the target RNA. These ASOs strongly inhibited gene expression only when the photocrosslinking rate was faster than the random walk of branch migration. In addition, pcASOs containing CNV D or CNV K targeted the RNAs with secondary structures. These results indicate the regulatory effect of photocrosslinker and photoirradiation energy using pcASOs on the gene expression level.

DNA Photocrosslinking Using 3-Vinylcarbazole Derivatives in Two-color Detection of Methylcytosine

The methylated DNA base 5-methylcytosine (mC) is the most important factor in the epigenetic regulation of gene expression. 3-cyanovinylcarbazole nucleoside (CNVK) photocrosslinks with mC more rapidly than with cytosine (C). In the present study, we evaluated the effect of the substituents of various 3-vinylcarbazole derivatives on mC- and C-mediated DNA photocrosslinking for the quantitative detection of mC. We also demonstrated the quantitative detection of mC via photocrosslinking using 3-vinylcarbazole derivatives on a DNA chip. The results suggest that this photocrosslinking reaction has potential for the selective detection of mC in DNA strands via photocrosslinking using 3-cyanovinylcarbazole derivatives.

Effect of nucleobase change on cytosine deamination through DNA photo-cross-linking reaction via 3-cyanovinylcarbazole nucleoside.

Photo-chemical deamination of cytosine using 3-cyanovinylcarbazole nucleoside (CNVK) mediated photo-cross-linking is a technique for site-directed mutagenesis. Using this technique in vivo requires the elimination of a high-temperature incubation step; instead, incubation should be carried out under physiological conditions. To improve the reactivity of CNVK mediated photo-cross-link induced deamination of cytosine under physiological conditions, an evaluation of base pairing in cytosine was carried out with respect to its deamination. Guanine was replaced with 4 different counter bases (inosine, 2-aminopurine, 5-nitroindole, and nebularine), showing distinct hydrogen bonding patterns with target cytosine, which was incorporated at the -1 position with respect to CNVK in the CNVK-modified photo-responsive oligodeoxyribonucleotides to ascertain the role of hydrogen bonding in deamination under physiological conditions. Among the counter bases, inosine showed the highest acceleration towards the photo-induced deamination reaction.

RNA fluorescence in situ hybridization using 3-cyanovinylcarbazole modified oligodeoxyribonucleotides as photo-cross-linkable probes

Photo-cross-linkable fluorescent oligodeoxyribonucleotides having 3-cyanovinylcarbazole nucleoside were applied to fluorescence in situ hybridization (FISH) based 16S rRNA detection in Escherichia coli cells. As the photo-cross-linked probe/rRNA hybrid was stable under the denaturing condition, decrease of the fluorescence signal through the washing process was prevented. The thermally irreversible hybridization property also enabled stable hybridization with the structured region on the target RNA, and facilitated design of the sequence for the FISH probe. Further development of the method might contribute to quantitative and stable FISH staining.

Sequence-Specific DNA Photosplitting of Crosslinked DNAs Containing the 3-Cyanovinylcarbazole Nucleoside by Using DNA Strand Displacement.

An oligodeoxynucleotide (ODN) containing the ultrafast reversible 3-cyanovinylcarbazole ((CNV) K) photo-crosslinker was photo-crosslinked to a complementary strand upon exposure to 366 nm irradiation and photosplit by use of 312 nm irradiation. In this paper we report that the photoreaction of (CNV) K on irradiation at 366 nm involves a photostationary state and that its reaction can be controlled by temperature. Guided by this new insight, we proposed and have now demonstrated previously unknown photosplitting of (CNV) K aided by DNA strand displacement as an alternative to heating. The photo-crosslinked double-stranded DNA (dsDNA) underwent >80 % photosplitting aided by DNA strand displacement on irradiation at 366 nm without heating. In this photosplitting based on DNA strand displacement, the relative thermal stability of the invader strand with respect to the template strands plays an important role, and an invader strand/template strand system that is more stable than the passenger strand/template strand system induces photosplitting without heating. This new strand-displacement-aided photosplitting occurred in a sequence-specific manner through irradiation at 366 nm in the presence of an invader strand.

A versatile puromycin-linker using cnvK for high-throughput in vitro selection by cDNA display

cDNA display is a powerful in vitro display technology used to explore functional peptides and proteins from a huge library by in vitro selection. In addition to expediting the in vitro selection cycle by using cDNA display, easy and rapid functional analysis of selected candidate clones is crucial for high-throughput screening of functional peptides and proteins. In this report, a versatile puromycin-linker employing an ultrafast photo-cross-linker, 3-cyanovinylcarbazole nucleoside, is introduced. Its utility for both in vitro selection using cDNA display and protein–protein interaction analysis using a surface plasmon resonance (SPR) system is described. Using this versatile puromycin-linker, we demonstrated the model in vitro selection of the FLAG epitope and a SPR-based assay to measure the dissociation constant between the B domain of protein A and immunoglobulin G. Improvement of the puromycin-linker as described herein should make the cDNA display method easier to utilize for design of protein or peptide based affinity reagents.

Critical Effect of Base Pairing of Target Pyrimidine on the Interstrand Photo-Cross-Linking of DNA via 3-Cyanovinylcarbazole Nucleoside.

To evaluate the effect of base pairing of the target pyrimidine on the interstrand photo-cross-linking reaction of DNA via 3-cyanovinylcarbazole nucleoside ((CNV)K), a complementary base of target pyrimidine was substituted with noncanonical purine bases or 1,3-propandiol (S). As the decrease of the hydrogen bonds in the base pairing of target C accelerated the photo-cross-linking reaction markedly (3.6- to 7.7-fold), it can be concluded that the number of hydrogen bonds in the base pairing, i.e., the stability of base pairing, of the target pyrimidine plays a critical role in the interstrand photo-cross-linking reaction. In the case of G to S substitution, the highest photoreactivity toward C was observed, whose photoreaction rate constant (k = 2.0 s(-1)) is comparable to that of (CNV)K toward T paired with A (k = 3.5 s(-1)). This is the most reactive photo-cross-linking reaction toward C in the sequence specific interstrand photo-cross-linking. This might facilitate the design of the photo-cross-linkable oligodeoxyribonucleotides for various target sequences.

Photo-regulation of constitutive gene expression in living cells by using ultrafast photo-cross-linking oligonucleotides.

3-Cyanovinylcarbazole nucleoside (CNVK), which has an ultrafast photo-cross-linking ability to complementary RNA, was incorporated into the antisense oligonucleotide targeting green fluorescent protein (GFP) mRNA. We successfully demonstrated that the photoreactive antisense oligonucleotides effectively regulate GFP expression in a stable cell line expressing the GFP gene in a photo-responsive manner.

Details of the Ultrafast DNA Photo-Cross-Linking Reaction of 3-Cyanovinylcarbazole Nucleoside: Cis–Trans Isomeric Effect and the Application for SNP-Based Genotyping

To clarify the cis-trans isomeric effect on the ultrafast DNA photo-cross-linking reaction of 3-cyanovinylcarbazole nucleoside ((CNV)K) in the DNA duplex, which gives a single photodimer on the reversed-phase HPLC chromatogram, the kinetics of the cis-trans photoisomerization of (CNV)K in double-stranded DNA was evaluated. Since the photoisomerization rate constant for cis to trans isomerization in double-stranded DNA was significantly larger than that for trans to cis isomerization, and the thermodynamic stability of the trans isomer was higher than that of the cis isomer, it was strongly suggested that the trans isomer of (CNV)K is a reactive species of the photo-cross-linking reaction. (1)H-(1)H NOESY analysis of the photoadduct consisting of (CNV)K and T also supported the trans-mediated photo-cross-linking reaction of (CNV)K. By using this ultrafast photo-cross-linking reaction for the molecular beacon-based SNPs typing, four individual Japanese rice strains were clearly distinguishable with simple photoirradiation and fluorescence imaging using double-stranded target DNAs.

Geometric Effect on the Photocrosslinking Reaction between 3‐Cyanovinylcarbazole Nucleoside and Pyrimidine Base in DNA/RNA Heteroduplex

To clarify the geometric effect of the ultra-fast photocrosslinking reaction of photoreactive oligodeoxyribonucleotide containing 3-cyanovinylcarbazole nucleoside ((CNV)K) on uridine in complementary RNA strands, pseudouridine (Ψ), which is an isomer of uridine with a C5-C1' glycosidic bond, was introduced to the photocrosslink site of (CNV)K in complementary RNA instead of U. The photoreactivity of (CNV)K toward Ψ was two-fold lower than that of U, suggesting that the geometry between the vinyl moiety on (CNV)K and the reactive double bond in the pyrimidine base has a large affect on the photoreactivity of (CNV)K. Contrary to the case of U, the reactivity of the (CNV)K toward Ψ was decreased by the decrease of reaction temperature below the Tm of heteroduplex, suggesting that the flexible structure of the duplex is advantageous for the photocrosslinking reaction with Ψ, whose reactive double bond possesses unfavorable geometry for the photocrosslinking reaction with (CNV)K. These basic findings might contribute to the development of a geometry selective photocrosslinking reaction. This is the first example of a sequence specific photocrosslinking reaction toward Ψ, which is the most abundant posttranscriptionally modified nucleoside.

Quick, Selective and Reversible Photocrosslinking Reaction between 5-Methylcytosine and 3-Cyanovinylcarbazole in DNA Double Strand

Selective photocrosslinking reaction between 3-cyanovinylcarbazole nucleoside (CNVK) and 5-methylcytosine (mC), which is known as epigenetic modification in genomic DNA, was developed. The reaction was completely finished within 5 s of 366 nm irradiation, and the rate of this photocrosslinking reaction was ca. 30-fold higher than that in the case of unmodified normal cytosine. There were no significant differences in the thermodynamic parameters and the kinetics of hybrid formation of oligonucleotide (ODN) containing CNVK and its complementary ODN containing C or mC at the photocrosslinking site, and suggesting that the quick and selective photoreaction has potential for the selective detection of mC in the DNA strand via the photocrosslinking reaction.

Quick and reversible photocrosslinking reaction of 3-cyanovinylcarbazole nucleoside in a DNA triplex

3-Cyanovinylcarbazole nucleoside ((CNV)K), which can quickly photocrosslink to the pyrimidine base in the DNA double strand, was incorporated into a triplex forming oligonucleotide (TFO). We successfully demonstrated that (CNV)K in TFO can photocrosslink to the thymine base in Watson-Crick double-stranded DNA via anti-Hoogsteen base pairing with a few seconds of photoirradiation.

Quick regulation of mRNA functions by a few seconds of photoirradiation

3-Cyanovinylcarbazole nucleoside, which effectively photocrosslinks to the pyrimidine base in complementary RNA strands, was incorporated into antisense oligonucleotides, and we evaluated the photoreactivity and the sequence selectivity to mutated K-ras oligoRNAs, as well as the regulation of the function of K-ras mRNA. We demonstrated that the reverse transcription and the translation activity of K-ras mRNA were quickly suppressed by a few seconds of photoirradiation with the addition of the photoresponsive antisense ODN.

Specific and reversible photochemical labeling of plasmid DNA using photoresponsive oligonucleotides containing 3-cyanovinylcarbazole

To develop a covalent and specific labeling method for single- and double-stranded plasmid DNA, photoresponsive oligonucleotide containing 3-cyanovinylcarbazole nucleoside was adopted. Single- and double-stranded plasmid DNA was successfully labeled/de-labeled with Cy3 and/or biotin by photoirradiation.

Photoreversible DNA end capping for the formation of hairpin structures

We describe a photoreversible DNA end capping via 3-cyanovinylcarbazole nucleoside. Doubly end-capped oligodeoxynucleotide (ODN) exhibits increased stability against snake venom phosphodiesterase and shows high thermal stability.

Site-specific photochemical RNA editing

Photo-induced artificial RNA editing was demonstrated using photo-reactive oligonucleotides containing 3-cyanovinylcarbazole nucleoside. This non-enzymatic and sequence-specific methodology will make a major contribution to the elucidation of RNA functions including non-coding RNAs and to the development of drugs based on sequence-specific RNA editing.

Development of a rapid and reversible photocrosslinking of RNA

We describe a novel reversible interstrand photocrosslinking reaction of RNA. In this system, a modified oligodeoxynucleotide (ODN) containing 3-cyanovinylcarbazole nucleoside ((CNV)K) reacts by photoirradiation at 366 nm for 1 s with pyrimidine residue of a complementary template RNA to yield a crosslinked product in 94% yield.