Synergistic DNA- and Protein-Based Recognition Promote an RNA-Templated Bio-orthogonal Reaction.
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ABSTRACT:
SUBMITTER: McLoughlin NM
PROVIDER: S-EPMC8362040 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:RNA can act as a template for DNA synthesis in the reverse transcription of retroviruses and retrotransposons and in the elongation of telomeres. Despite its abundance in the nucleus, there has been no evidence for a direct role of RNA as a template in the repair of any chromosomal DNA lesions, including DNA double-strand breaks (DSBs), which are repaired in most organisms by homologous recombination or by non-homologous end joining. An indirect role for RNA in DNA repair, following reverse transcription and formation of a complementary DNA, has been observed in the non-homologous joining of DSB ends. In the yeast Saccharomyces cerevisiae, in which homologous recombination is efficient, RNA was shown to mediate recombination, but only indirectly through a cDNA intermediate generated by the reverse transcriptase function of Ty retrotransposons in Ty particles in the cytoplasm. Although pairing between duplex DNA and single-strand (ss)RNA can occur in vitro and in vivo, direct homologous exchange of genetic information between RNA and DNA molecules has not been observed. We show here that RNA can serve as a template for DNA synthesis during repair of a chromosomal DSB in yeast. The repair was accomplished with RNA oligonucleotides complementary to the broken ends. This and the observation that even yeast replicative DNA polymerases such as alpha and delta can copy short RNA template tracts in vitro demonstrate that RNA can transfer genetic information in vivo through direct homologous interaction with chromosomal DNA.
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Project description:Nucleic acids detection is essential to the study of biological processes and to diagnosis of pathological states. Although PCR is highly effective in vitro, methods that can function without prior sample preparation, thermal cycling, or enzymes are of interest due to their simplicity. Most current non-PCR detection methods rely on linear signal amplification, which hinders the detection of small amounts of genetic material. To address this limitation, we tested a new strategy for attaining higher-order signal amplification, in which a target sequence templates a chemical ligation, and the product of this reaction is in turn detected with a second templated reaction. The method is nonenzymatic, isothermal, and fluorogenic, allowing the direct detection of nucleic acids in complex matrices. Using this approach, as little as 500 attomoles (10 pM) could be detected with single nucleotide resolution. In a test of selectivity, single nucleotide substitutions and deletions could successfully be detected, including a deletion that is associated with tetracycline resistance in Helicobacter pylori. Compatibility with biological matrices was demonstrated by the direct detection of rRNA in bacterial lysate. Imaging and detection of target sequences on a solid support further illustrates the potential of the new approach for high-throughput analysis.
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Project description:Chemo-photothermal synergistic treatment has a high potential to complement traditional cancer therapy and amplify its outcome. Precision in the delivery of these therapeutic agents to tumor cells has been indicated as being key to maximizing their therapeutic effects. Method: We developed a bio-orthogonal copper-free click-targeting nanocomposite system (DLQ/DZ) that markedly improved specific co-delivery of the chemotherapeutic agent doxorubicin and the photosensitizer zinc phthalocyanine to breast cancer cells via a two-step mechanism. In the first step, an azide-modified sugar (tetraacetylated N-azidoacetyl-D-mannosamine, Ac4ManNAz) was injected intratumorally for glycoengineering of the tumor cell surface. Subsequently, DLQ/DZ was administered to achieve tumor enrichment via bio-orthogonal copper-free click-targeting. Results: During the first step in our experiments, high density azide groups (3.23×107/cell) were successfully glycoengineered on the surface of tumor cells following Ac4ManNAz administration in vitro. Subsequently, the highly efficient bio-orthogonal click chemical reaction between receptor-like azide groups on tumor cells and DBCO on nanocomposites significantly enhanced the cellular uptake and tumor-specific distribution (4.6x increase) of the nanocomposites in vivo. Importantly, Ac4ManNAz+DLQ/DZ treatment augmented the anti-cancer effect of combined chemotherapy and PTT (96.1% inhibition rate), nearly ablating the tumor. Conclusions: This bio-orthogonal click-targeting combination strategy may provide a promising treatment approach for surficial breast cancers.
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Project description:Background: Protein theranostics integrate both diagnostic and treatment functions on a single disease-targeting protein. However, the preparation of these multimodal agents remains a major challenge. Ideally, conventional recombinant proteins should be used as starting materials for modification with the desired detection and therapeutic functionalities, but simple chemical strategies that allow the introduction of two different modifications into a protein in a site-specific manner are not currently available. We recently discovered two highly efficient peptide ligases, namely butelase-1 and VyPAL2. Although both ligate at asparaginyl peptide bonds, these two enzymes are bio-orthogonal with distinguishable substrate specificities, which can be exploited to introduce distinct modifications onto a protein. Methods: We quantified substrate specificity differences between butelase-1 and VyPAL2, which provide orthogonality for a tandem ligation method for protein dual modifications. Recombinant proteins or synthetic peptides engineered with the preferred recognition motifs of butelase-1 and VyPAL2 at their respective C- and N-terminal ends could be modified consecutively by the action of the two ligases. Results: Using this method, we modified an EGFR-targeting affibody with a fluorescein tag and a mitochondrion-lytic peptide at its respective N- and C-terminal ends. The dual-labeled protein was found to be a selective bioimaging and cytotoxic agent for EGFR-positive A431 cancer cells. In addition, the method was used to prepare a cyclic form of the affibody conjugated with doxorubicin. Both modified affibodies showed increased cytotoxicity to A431 cells by 10- and 100-fold compared to unconjugated doxorubicin and the free peptide, respectively. Conclusion: Bio-orthogonal tandem ligation using two asparaginyl peptide ligases with differential substrate specificities is a straightforward approach for the preparation of multifunctional protein biologics as potential theranostics.
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Project description:RNA presents intringuing roles in many cellular processes and its versatility underpins many different applications in synthetic biology. Nonetheless, RNA origami as a method for nanofabrication is not yet fully explored and the majority of RNA nanostructures are based on natural pre-folded RNA. Here we describe a biologically inert and uniquely addressable RNA origami scaffold that self-assembles into a nanoribbon by seven staple strands. An algorithm is applied to generate a synthetic De Bruijn scaffold sequence that is characterized by the lack of biologically active sites and repetitions larger than a predetermined design parameter. This RNA scaffold and the complementary staples fold in a physiologically compatible isothermal condition. In order to monitor the folding, we designed a new split Broccoli aptamer system. The aptamer is divided into two nonfunctional sequences each of which is integrated into the 5' or 3' end of two staple strands complementary to the RNA scaffold. Using fluorescence measurements and in-gel imaging, we demonstrate that once RNA origami assembly occurs, the split aptamer sequences are brought into close proximity forming the aptamer and turning on the fluorescence. This light-up 'bio-orthogonal' RNA origami provides a prototype that can have potential for in vivo origami applications.
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Project description:Homologous recombination is a molecular process that has multiple important roles in DNA metabolism, both for DNA repair and genetic variation in all forms of life. Generally, homologous recombination involves the exchange of genetic information between two identical or nearly identical DNA molecules; however, homologous recombination can also occur between RNA molecules, as shown for RNA viruses. Previous research showed that synthetic RNA oligonucleotides can act as templates for DNA double-strand break (DSB) repair in yeast and human cells, and artificial long RNA templates injected in ciliate cells can guide genomic rearrangements. Here we report that endogenous transcript RNA mediates homologous recombination with chromosomal DNA in yeast Saccharomyces cerevisiae. We developed a system to detect the events of homologous recombination initiated by transcript RNA following the repair of a chromosomal DSB occurring either in a homologous but remote locus, or in the same transcript-generating locus in reverse-transcription-defective yeast strains. We found that RNA-DNA recombination is blocked by ribonucleases H1 and H2. In the presence of H-type ribonucleases, DSB repair proceeds through a complementary DNA intermediate, whereas in their absence, it proceeds directly through RNA. The proximity of the transcript to its chromosomal DNA partner in the same locus facilitates Rad52-driven homologous recombination during DSB repair. We demonstrate that yeast and human Rad52 proteins efficiently catalyse annealing of RNA to a DSB-like DNA end in vitro. Our results reveal a novel mechanism of homologous recombination and DNA repair in which transcript RNA is used as a template for DSB repair. Thus, considering the abundance of RNA transcripts in cells, RNA may have a marked impact on genomic stability and plasticity.
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