Dynamic modifications of biomacromolecules: mechanism and chemical interventions

Sulfur-based fluorescent probes for biological analysis: A review

The widespread adoption of small-molecule fluorescence detection methodologies in scientific research and industrial contexts can be ascribed to their inherent merits, including elevated sensitivity, exceptional selectivity, real-time detection capabilities, and non-destructive characteristics. In recent years, there has been a growing focus on small-molecule fluorescent probes engineered with sulfur elements, aiming to detect a diverse array of biologically active species. This review presents a comprehensive survey of sulfur-based fluorescent probes published from 2017 to 2023. The diverse repertoire of recognition sites, including but not limited to N, N-dimethylthiocarbamyl, disulfides, thioether, sulfonyls and sulfoxides, thiourea, thioester, thioacetal and thioketal, sulfhydryl, phenothiazine, thioamide, and others, inherent in these sulfur-based probes markedly amplifies their capacity for detecting a broad spectrum of analytes, such as metal ions, reactive oxygen species, reactive sulfur species, reactive nitrogen species, proteins, and beyond. Owing to the individual disparities in the molecular structures of the probes, analogous recognition units may be employed to discern diverse substrates. Subsequent to this classification, the review provides a concise summary and introduction to the design and biological applications of these probe molecules. Lastly, drawing upon a synthesis of published works, the review engages in a discussion regarding the merits and drawbacks of these fluorescent probes, offering guidance for future endeavors.

Discovery of Photoexcited 2-Chloro-3,5-Dinitrobenzoic Acid as a Chemical Deprenylase of i6A RNA

RNA modifications play crucial roles in regulating gene expression and cellular homeostasis. Modulating RNA modifications, particularly by targeting the enzymes responsible for their catalysis, has emerged as a promising therapeutic strategy. However, limitations, such as the lack of identified modifying enzymes and compensatory mechanisms, hinder targeted interventions. Chemical approaches independent of enzymatic activity offer an alternative strategy for RNA modification modulation. Here, we present the identification of 2-chloro-3,5-dinitrobenzoic acid as a highly effective photochemical deprenylase of i6A RNA. This method demonstrates exceptional selectivity towards i6A, converting its substituent into a "N-doped" ozonide, which upon hydrolysis releases natural adenine. We believe that this chemical approach will pave the way for a better understanding of RNA modification biology and the development of novel therapeutic modalities.

Nanopore Identification of N-Acetylation by Hydroxylamine Deacetylation (NINAHD)

N-Acetyl modification, a chemical modification commonly found on biomacromolecules, plays a crucial role in the regulation of cell activities and is related to a variety of diseases. However, due to the instability of N-acetyl modification, accurate and rapid identification of N-acetyl modification with a low measurement cost is still technically challenging. Here, based on hydroxylamine deacetylation and nanopore single molecule chemistry, a universal sensing strategy for N-acetyl modification has been developed. Acetohydroxamic acid (AHA), which is produced by the hydroxylamine deacetylation reaction and serves as a reporter for N-acetylation identification, is specifically sensed by a phenylboronic acid (PBA)-modified Mycobacterium smegmatis porin A (MspA). With this strategy, N-acetyl modifications on RNA, DNA, proteins, and glycans were identified, demonstrating its generality. Specifically, histones can be treated with hydroxylamine deacetylation, from which the generated AHA can represent the amount of N-acetyl modification detected by a nanopore sensor. The unique event features of AHA also demonstrate the robustness of sensing against other interfering analytes in the environment.

Synthesizing biomaterials in living organisms

Living organisms fabricate biomacromolecules such as DNA, RNA, and proteins by the self-assembly process. The research on the mechanism of biomacromolecule formation also inspires the exploration of in vivo synthesized biomaterials. By elaborate design, artificial building blocks or precursors can self-assemble or polymerize into functional biomaterials within living organisms. In recent decades, these so-called in vivo synthesized biomaterials have achieved extensive applications in cell-fate manipulation, disease theranostics, bioanalysis, cellular surface engineering, and tissue regeneration. In this review, we classify strategies for in vivo synthesis into non-covalent, covalent, and genetic types. The development of these approaches is based on the chemical principles of supramolecular chemistry and synthetic chemistry, biological cues such as enzymes and microenvironments, and the means of synthetic biology. By summarizing the design principles in detail, some insights into the challenges and opportunities in this field are provided to  enlighten further research.

Recent Advances towards the Reversible Chemical Modification of Proteins

Proteins are intriguing biomacromolecules for all living systems, not only as essential building blocks of organisms, but also as participants in almost every aspect of cellular activity such as metabolism and gene transcription/expression. Developing chemical biology tools that are capable of labeling/modifying proteins is a powerful method for decoding their detailed structures and functions. However, most current approaches heavily rely on the installation of permanent tags or genetic engineering of unnatural amino acids. There has been slow development in reversible chemical labeling using small organic probes and bioorthogonal transformations to construct site-selectively modified proteins and conditionally restore their activities or structures. This review summarizes recent advances in the field of chemical regulation of proteins with reversible transformations towards distinct motifs, including amino acid residues, amide backbones and native post-translational lysine. Finally, current challenges and future perspectives are discussed.

Loss of Wtap results in cerebellar ataxia and degeneration of Purkinje cells

N⁶-methyladenosine (m⁶A) modification, which is achieved by the METTL3/METTL14/WTAP methyltransferase complex, is the most abundant internal mRNA modification. Although recent evidence indicates that m⁶A can regulate neurodevelopment as well as synaptic function, the roles of m⁶A modification in the cerebellum and related synaptic connections are not well established. Here, we report that Purkinje cell (PC)-specific WTAP knockout mice display early-onset ataxia concomitant with cerebellar atrophy due to extensive PC degeneration and apoptotic cell death. Loss of Wtap also causes the aberrant degradation of multiple PC synapses. WTAP depletion leads to decreased expression levels of METTL3/14 and reduced m⁶A methylation in PCs. Moreover, the expression of GFAP and NF-L in the degenerating cerebellum is increased, suggestive of severe neuronal injuries. In conclusion, this study demonstrates the critical role of WTAP-mediated m⁶A modification in cerebellar PCs, thus providing unique insights related to neurodegenerative disorders.

Chemical methods for studying the crosstalk between histone H2B ubiquitylation and H3 methylation

The reversible and dynamic post-translational modifications (PTMs) of histones in eukaryotic chromatin are intimately connected to cell development and gene function, and abnormal regulation of PTMs can result in cancer and neurodegenerative diseases. Specific combinations of these modifications are mediated by a series of chromatin proteins that write, erase, and read the "histone codes," but mechanistic studies of the precise biochemical and structural relationships between different sets of modifications and their effects on chromatin function constitute a unique challenge to canonical biochemical approaches. In the past decade, the development and application of chemical methods for investigating histone PTM crosstalks has received considerable attention in the field of chemical biology. In this review, taking the functional crosstalk between H2B ubiquitylation at Lys120 (H2BK120ub) and H3 methylation at Lys79 (H3K79me) as a typical example, we survey recent developments of different chemical methods, in particular, protein synthetic chemistry and protein-based chemical probes, for studying the mechanism of the functional crosstalks of histone PTMs.

Research fronts of Chemical Biology

Over the past decades, researchers have witnessed substantially increasing and ever-growing interests and efforts in Chemical Biology studies, thanks to the development of genome and epi-genome sequencing (revealing potential drug targets), synthetic chemistry (producing new medicines), bioorthogonal chemistry (chemistry in living systems) and high-throughput screening technologies (in vitro cell systems, protein binding assays and phenotypic assays). This report presents literature search results for current research in Chemical Biology, to explore basic principles, summarize recent advances, identify key challenges, and provide suggestions for future research (with a focus on Chemical Biology in the context of human health and diseases). Chemical Biology research can positively contribute to delivering a better understanding of the molecular and cellular mechanisms that accompany pathology underlying diseases, as well as developing improved methods for diagnosis, drug discovery, and therapeutic delivery. While much progress has been made, as shown in this report, there are still further needs and opportunities. For instance, pressing challenges still exist in selecting appropriate targets in biological systems and adopting more rational design strategies for the development of innovative and sustainable diagnostic technologies and medical treatments. Therefore, more than ever, researchers from different disciplines need to collaborate to address the challenges in Chemical Biology.

Global chemical modifications comparison of human plasma proteome from two different age groups

In this study, two groups of human plasma proteome at different age groups (old and young) were used to perform a comparison of global chemical modifications, as determined by tandem mass spectrometry (MS/MS) combined with non-limiting modification identification algorithms. The sulfhydryl in the cysteine A total of 4 molecular modifications were found to have significant differences passing random grouping tests: the succinylation and phosphorylation modification of cysteine (Cys, C) and the modification of lysine (Lys, K) with threonine (Thr, T) were significantly higher in the old group than in the young group, while the carbamylation of lysine was lower in the young group. We speculate that there is an increase in certain modified proteins in the blood of the old people which, in turn, changes the function of those proteins. This change may be one of the reasons why old people are more likely than young people to be at risk for age-related diseases, such as metabolic diseases, cerebral and cardiovascular diseases, and cancer.