We report the first cellular application of a photoclick SPAAC reagent to label azide-functionalized RNA. 350 nm irradiation of a cyclopropenone caged oxo-dibenzocyclooctyne (photo-ODIBO) biotin ...yields formation of the SPAAC reactive species, which rapidly forms adducts with RNA containing 2′-azidoadenosine (2′N3-A). Photo-ODIBO was found to be highly stable in the presence of thiols, conferring greater stability relative to ODIBO. Light activated photo-ODIBO enabled tagging of cellular RNA, in addition to fluorescent imaging as well as enrichment of RNA in cell subpopulations via selective irradiation.
Tissues and organs are composed of diverse cell types, which poses a major challenge for cell-type-specific profiling of gene expression. Current metabolic labeling methods rely on exogenous ...pyrimidine analogs that are only incorporated into RNA in cells expressing an exogenous enzyme. This approach assumes that off-target cells cannot incorporate these analogs. We disprove this assumption and identify and characterize the enzymatic pathways responsible for high background incorporation. We demonstrate that mammalian cells can incorporate uracil analogs and characterize the enzymatic pathways responsible for high background incorporation. To overcome these limitations, we developed a new small molecule-enzyme pair consisting of uridine/cytidine kinase 2 and 2'-azidouridine. We demonstrate that 2'-azidouridine is only incorporated in cells expressing uridine/cytidine kinase 2 and characterize selectivity mechanisms using molecular dynamics and X-ray crystallography. Furthermore, this pair can be used to purify and track RNA from specific cellular populations, making it ideal for high-resolution cell-specific RNA labeling. Overall, these results reveal new aspects of mammalian salvage pathways and serve as a new benchmark for designing, characterizing and evaluating methodologies for cell-specific labeling of biomolecules.
DNA modification is known to regulate experience-dependent gene expression. However, beyond cytosine methylation and its oxidated derivatives, very little is known about the functional importance of ...chemical modifications on other nucleobases in the brain. Here we report that in adult mice trained in fear extinction, the DNA modification N6-methyl-2'-deoxyadenosine (m6dA) accumulates along promoters and coding sequences in activated prefrontal cortical neurons. The deposition of m6dA is associated with increased genome-wide occupancy of the mammalian m6dA methyltransferase, N6amt1, and this correlates with extinction-induced gene expression. The accumulation of m6dA is associated with transcriptional activation at the brain-derived neurotrophic factor (Bdnf) P4 promoter, which is required for Bdnf exon IV messenger RNA expression and for the extinction of conditioned fear. These results expand the scope of DNA modifications in the adult brain and highlight changes in m6dA as an epigenetic mechanism associated with activity-induced gene expression and the formation of fear extinction memory.
Insulin-degrading enzyme (IDE) is an atypical zinc-metalloendopeptidase that hydrolyzes insulin and other intermediate-sized peptide hormones, many of which are implicated in skin health and wound ...healing. Pharmacological inhibitors of IDE administered internally have been shown to slow the breakdown of insulin and thereby potentiate insulin action. Given the importance of insulin and other IDE substrates for a variety of dermatological processes, pharmacological inhibitors of IDE suitable for topical applications would be expected to hold significant therapeutic and cosmetic potential. Existing IDE inhibitors, however, are prohibitively expensive, difficult to synthesize and of undetermined toxicity. Here we used phage display to discover novel peptidic inhibitors of IDE, which were subsequently characterized in vitro and in cell culture assays. Among several peptide sequences tested, a cyclic dodecapeptide dubbed P12-3A was found to potently inhibit the degradation of insulin (Ki = 2.5 ± 0.31 μM) and other substrates by IDE, while also being resistant to degradation, stable in biological milieu, and highly selective for IDE. In cell culture, P12-3A was shown to potentiate several insulin-induced processes, including the transcription, translation and secretion of alpha-1 type I collagen in primary murine skin fibroblasts, and the migration of keratinocytes in a scratch wound migration assay. By virtue of its potency, stability, specificity for IDE, low cost of synthesis, and demonstrated ability to potentiate insulin-induced processes involved in wound healing and skin health, P12-3A holds significant therapeutic and cosmetic potential for topical applications.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Optimized and stringent chemical methods to profile nascent RNA expression are still in demand. Herein, we expand the toolkit for metabolic labeling of RNA through application of inverse electron ...demand Diels–Alder (IEDDA) chemistry. Structural examination of metabolic enzymes guided the design and synthesis of vinyl-modified nucleosides, which we systematically tested for their ability to be installed through cellular machinery. Further, we tested these nucleosides against a panel of tetrazines to identify those which are able to react with a terminal alkene, but are stable enough for selective conjugation. The selected pairings then facilitated RNA functionalization with biotin and fluorophores. We found that this chemistry not only is amenable to preserving RNA integrity but also endows the ability to both tag and image RNA in cells. These key findings represent a significant advancement in methods to profile the nascent transcriptome using chemical approaches.
In this Perspective, we expand the notion of temporal regulation of RNA in the brain and propose that the qualitative nature of RNA and its metabolism, together with RNA abundance, are essential for ...the molecular mechanisms underlying experience-dependent plasticity. We discuss emerging concepts in the newly burgeoning field of epitranscriptomics, which are predicted to be heavily involved in cognitive function. These include activity-induced RNA modifications, RNA editing, dynamic changes in the secondary structure of RNA, and RNA localization. Each is described with an emphasis on its role in regulating the function of both protein-coding genes, as well as various noncoding regulatory RNAs, and how each might influence learning and memory.
Stringent chemical methods to profile RNA expression within discrete cellular populations remains a key challenge in biology. To address this issue, we developed a chemical–genetic strategy for ...metabolic labeling of RNA. Cell-specific labeling of RNA can be profiled and imaged using bioorthogonal chemistry. We anticipate that this platform will provide the community with a much-needed chemical toolset for cell-type specific profiling of cell-specific transcriptomes derived from complex biological systems.
Real‐time tracking of RNA expression can provide insight into the mechanisms used to generate cellular diversity, as well as help determine the underlying causes of disease. Here we present the ...exploration of azide‐modified nucleoside analogues and their ability to be metabolically incorporated into cellular RNA. We report robust incorporation of adenosine analogues bearing azide handles at both the 2′‐ and N6‐positions; 5‐methylazidouridine was not incorporated into cellular RNA. We further demonstrate selectivity of our adenosine analogues for transcription and polyadenylation. We predict that azidonucleosides will find widespread utility in examining RNA functions inside living cells, as well as in more complex systems such as tissues and living animals.
Azide Functionality, Inc. We explored azidonucleoside incorporation into cellular RNA, revealing selectivity for azidoadenosine analogues and no incorporation of 5‐azidouridine. This expansion of the bioorthogonal toolkit for RNA will further investigation into RNA expression and processing and provide a platform for analyzing the growing list of RNA functions beyond protein encoding.
Proper control and maintenance of gene expression is critical for cellular identity and maintenance. Transcription of RNA from the genome is intimately controlled by post-translational chemical ...modification of histone tails and DNA. Recent studies have demonstrated that chromatin-remodeling complexes seek out their target genomic loci through the help of noncoding RNA molecules. Within this Review, we will outline how the use of biochemical techniques has shed light on the mechanisms employed by RNA to guide these complexes and therefore control gene expression.
The transcriptional landscape has revealed itself to be highly complex, wherein RNA serves both coding and non-coding functions that are essential for cell differentiation, development and survival. ...Because the role of RNA has continued to expand, there is increasing need for biochemical methods to label and track RNA transcription, post-transcriptional regulation, and other RNA-based mechanisms. Herein, my doctoral work to expand the scope of metabolic reporters for RNA synthesis details a systematic expansion of chemistries and modifications for nucleoside analogs. This work has also served as a foundation for the development of novel, cell-specific RNA tagging approaches, both chemical and enzymatic. Throughout these studies, I have characterized the limitations of functional group tolerance and in many cases interrogated their effects on cell uptake and metabolism. Furthermore, I have worked to characterize the limitations of current cell-specific methods, with the goal of developing more stringent and robust approaches. These efforts are poised to provide greater context and engineering opportunities for methods to tag, visualize and study RNA gene expression.
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