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PubMed2026

Human Umbilical Cord Mesenchymal Stem Cells in Metabolic Dysfunction-associated Fatty Liver Disease (MAFLD) Therapy: Mechanisms, Clinical Efficacy, and Future Perspectives.

There is currently no approved drug treatment for metabolic dysfunction-related fatty liver disease (MAFLD). Umbilical cord-derived mesenchymal stem cells (UC-MSCs) show therapeutic potential, but their mechanism of action is remains incompletely understood. Different from previous reviews that focused on a single pathway, this article presents three important contributions: First, it constructs an integrated "multi-target synergy network" model, clarifying how UC-MSCs coordinate and regulate the inflammatory, metabolic and fibrotic processes through the interactions between the AMPK/mTOR, Nrf2/HO-1 and TGF-β/Smad pathways; Second, it systematically assesses recent clinical trials (2022-2025), identifying several unaddressed barriers to transformation, including the lack of histological endpoint indicators, batch-to-batch differences, and the absence of dose exploration studies; Third, we integrate the latest developments from 2024 to 2025, particularly mitochondrial transfer (mediated by tunnel nanotubes and accompanied by quantitative efficacy data) and exosome circular RNA networks [Formula: see text], which have not been covered in previous reviews. Based on the above analysis, we also propose specific suggestions for standardized GMP production, mandatory genomic stability testing, and long-term safety registration. This review provides a comprehensive analysis of elaborates on the treatment of MAFLD with UC-MSCs from a mechanistic and translational perspective, based on the extensive updates of relevant literature.

Humans↗
PubMed2006

Sequence-specific RNA binding mediated by the RNase PH domain of components of the exosome.

We have previously demonstrated that PM-Scl-75, a component of the human exosome complex involved in RNA maturation and mRNA decay, can specifically interact with RNAs containing an AU-rich instability element. Through the analysis of a series of deletion mutants, we have now shown that a 266 amino acid fragment representing the RNase PH domain is responsible for the sequence-specific binding to AU-rich elements. Furthermore, we found that the RNase PH domains from two other exosomal components, OIP2 and RRP41, as well as from Escherichia coli polynucleotide phosphorylase, are all capable of specifically interacting with RNAs containing an AU-rich element with similar affinities. Finally, we demonstrate that the interaction of the RNase PH domain of PM-Scl-75 is readily competed by poly(U), but only inefficiently using other homopolymeric RNAs. These data demonstrate that RNase PH domains in general have an affinity for U- and AU-rich sequences, and broaden the potential role in RNA biology of proteins containing these domains.

Base Composition↗
PubMed2005

Structural basis of 3' end RNA recognition and exoribonucleolytic cleavage by an exosome RNase PH core.

The exosome is a macromolecular complex that plays fundamental roles in the biogenesis and turnover of a large number of RNA species. Here we report the crystal structures of the Rrp41-Rrp42 core complex of the S. solfataricus exosome bound to short single-stranded RNAs and to ADP. The RNA binding cleft recognizes four nucleotides in a sequence-unspecific manner, mainly by electrostatic interactions with the phosphate groups. Interactions at the 2' hydroxyls of the sugars provide specificity for RNA over DNA. The structures show both the bound substrate and the cleaved product of the reaction, suggesting a catalytic mechanism for the 3'-5' phosphorolytic activity of the exosome.

Archaeal Proteins↗
PubMed2006

RNA polyadenylation and degradation in different Archaea; roles of the exosome and RNase R.

Polyadenylation is a process common to almost all organisms. In eukaryotes, stable poly(A)-tails, important for mRNA stability and translation initiation, are added to the 3' ends of most mRNAs. Contrarily, polyadenylation can stimulate RNA degradation, a phenomenon witnessed in prokaryotes, organelles and recently, for nucleus-encoded RNA as well. Polyadenylation takes place in hyperthermophilic archaea and is mediated by the archaeal exosome, but no RNA polyadenylation was detected in halophiles. Here, we analyzed polyadenylation in the third archaea group, the methanogens, in which some members contain genes encoding the exosome but others lack these genes. Polyadenylation was found in the methanogen, Methanopyrus kandleri, containing the exosome genes, but not in members which lack these genes. To explore how RNA is degraded in the absence of the exosome and without polyadenylation, we searched for the exoribonuclease that is involved in this process. No homologous proteins for any other known exoribonuclease were detected in this group. However, the halophilic archaea contain a gene homologous to the exoribonuclease RNase R. This ribonuclease is not able to degrade structured RNA better than PNPase. RNase R, which appears to be the only exoribonucleases in Haloferax volcanii, was found to be essential for viability.

Archaea↗
PubMed2026

Recent advancements in exosomal content analysis: the future of liquid biopsy.

Exosomes are widely acknowledged as an essential agent that carries biomarkers for specific diseases, representing the molecular status of their parent cells and providing extremely useful diagnostic insights. They can be isolated from different body fluids and contain a range of cargo molecules, including proteins, lipids, metabolites, and nucleic acids. Recent advancements in technology have greatly accelerated exosome research. Proteomics provides protein signatures linked to many pathological conditions, enabling quick and clinically scalable diagnostic tools, whereas high-throughput RNA-sequencing can be used to perform detailed transcriptome profiling. Exosomal biomarkers are showing promising clinical results in early detection of neurological diseases, infectious and cardiovascular disorders, oncology, and other medical conditions, hence accelerating therapeutic monitoring. Despite these advances, several challenges continue to hinder clinical translation including the lack of standardized isolation protocol, variability in exosome yield and purity, biological heterogeneity, and limited large-scale clinical validation. Addressing these limitations will be critical for the successful integration of exosome-based liquid biopsy into routine clinical practice. Overall, exosomes having significant potential as diagnostic tool, represent a transformative horizon in biomedical liquid biopsy research to redefine the landscape of less-invasive diagnostics and tailored clinical applications.

Humans↗
PubMed2003

Domain analysis of the chloroplast polynucleotide phosphorylase reveals discrete functions in RNA degradation, polyadenylation, and sequence homology with exosome proteins.

The molecular mechanism of mRNA degradation in the chloroplast consists of sequential events, including endonucleolytic cleavage, the addition of poly(A)-rich sequences to the endonucleolytic cleavage products, and exonucleolytic degradation. In spinach chloroplasts, the latter two steps of polyadenylation and exonucleolytic degradation are performed by the same phosphorolytic and processive enzyme, polynucleotide phosphorylase (PNPase). An analysis of its amino acid sequence shows that the protein is composed of two core domains related to RNase PH, two RNA binding domains (KH and S1), and an alpha-helical domain. The amino acid sequence and domain structure is largely conserved between bacteria and organelles. To define the molecular mechanism that controls the two opposite activities of this protein in the chloroplast, the ribonuclease, polymerase, and RNA binding properties of each domain were analyzed. The first core domain, which was predicted to be inactive in the bacterial enzymes, was active in RNA degradation but not in polymerization. Surprisingly, the second core domain was found to be active in degrading polyadenylated RNA only, suggesting that nonpolyadenylated molecules can be degraded only if tails are added, apparently by the same protein. The poly(A) high-binding-affinity site was localized to the S1 domain. The complete spinach chloroplast PNPase, as well as versions containing the core domains, complemented the cold sensitivity of an Escherichia coli PNPase-less mutant. Phylogenetic analyses of the two core domains showed that the two domains separated very early, resulting in the evolution of the bacterial and organelle PNPases and the exosome proteins found in eukaryotes and some archaea.

Amino Acid Sequence↗
PubMed2001

Prediction of the archaeal exosome and its connections with the proteasome and the translation and transcription machineries by a comparative-genomic approach.

By comparing the gene order in the completely sequenced archaeal genomes complemented by sequence profile analysis, we predict the existence and protein composition of the archaeal counterpart of the eukaryotic exosome, a complex of RNAses, RNA-binding proteins, and helicases that mediates processing and 3'->5' degradation of a variety of RNA species. The majority of the predicted archaeal exosome subunits are encoded in what appears to be a previously undetected superoperon. In Methanobacterium thermoautotrophicum, this predicted superoperon consists of 15 genes; in the Crenarchaea, Sulfolobus solfataricus and Aeropyrum pernix, one and two of the genes from the superoperon, respectively, are relocated in the genome, whereas in other Euryarchaeota, the superoperon is split into a variable number of predicted operons and solitary genes. Methanococcus jannaschii partially retains the superoperon, but lacks the three core exosome subunits, and in Halobacterium sp., the superoperon is divided into two predicted operons, with the same three exosome subunits missing. This suggests concerted gene loss and an alteration of the structure and function of the predicted exosome in the Methanococcus and Halobacterium lineages. Additional potential components of the exosome are encoded by partially conserved predicted small operons. Along with the orthologs of eukaryotic exosome subunits, namely an RNase PH and two RNA-binding proteins, the predicted archaeal exosomal superoperon also encodes orthologs of two protein subunits of RNase P. This suggests a functional and possibly a physical interaction between RNase P and the postulated archaeal exosome, a connection that has not been reported in eukaryotes. In a pattern of apparent gene loss complementary to that seen in Methanococcus and Halobacterium, Thermoplasma acidophilum lacks the RNase P subunits. Unexpectedly, the identified exosomal superoperon, in addition to the predicted exosome components, encodes the catalytic subunits of the archaeal proteasome, two ribosomal proteins and a DNA-directed RNA polymerase subunit. These observations suggest that in archaea, a tight functional coupling exists between translation, RNA processing and degradation, (apparently mediated by the predicted exosome) and protein degradation (mediated by the proteasome), and may have implications for cross-talk between these processes in eukaryotes.

Adenosine Triphosphatases↗
PubMed2006

Structure of the nuclear exosome component Rrp6p reveals an interplay between the active site and the HRDC domain.

The multisubunit eukaryotic exosome is an essential RNA processing and degradation machine. In its nuclear form, the exosome associates with the auxiliary factor Rrp6p, which participates in both RNA processing and degradation reactions. The crystal structure of Saccharomyces cerevisiae Rrp6p displays a conserved RNase D core with a flanking HRDC (helicase and RNase D C-terminal) domain in an unusual conformation shown to be important for the processing function of the enzyme. Complexes with AMP and UMP, the products of the RNA degradation process, reveal how the protein specifically recognizes ribonucleotides and their bases. Finally, in vivo mutational studies show the importance of the domain contacts for the processing function of Rrp6p and highlight fundamental differences between the protein and its prokaryotic RNase D counterparts.

Binding Sites↗
PubMed2006

Adenylation and exosome-mediated degradation of cotranscriptionally cleaved pre-messenger RNA in human cells.

In humans, polyadenylation of messenger RNA (mRNA) protects transcripts from degradation and enhances translation efficiency. Conversely, in bacteria, polyadenylation destabilizes mRNA. RNA adenylation was recently implicated in promoting degradation of some yeast RNAs by the exosome. The exosome complex of exoribonucleases is a major degradation machine in eukaryotes, and many of its components share significant homology with bacterial exonucleases. The human beta-globin pre-mRNA is cotranscriptionally cleaved within its 3' flank. Here, we show that some RNA ends, coinciding with these cotranscriptionally cleaved regions, contain short A tails on their 3' ends. Moreover, all of the pre-mRNA species detected accumulate in the absence of the exosome. We have also detected adenylation on RNA 3' ends originating within the mouse serum albumin (MSA) 3' flanking region RNA. This step in pre-mRNA degradation may represent an additional role for adenylation in mammals.

Animals↗
PubMed2025

A comprehensive analysis of supermere, exomere, and extracellular vesicle isolation and cargo in colorectal cancer.

Biofluids contain a heterogeneous mixture of extracellular vesicles and non-vesicular nanoparticles (including exomeres and supermeres) that transport a diverse array of proteins, RNA, and lipids. Our previous efforts to characterize the contents of these carriers in colorectal cancer relied on 2D culture systems requiring large-scale setups and time-consuming ultracentrifugation-based isolation. To streamline this process, we have combined 3D hollow-fiber bioreactor production and fast-protein liquid chromatography-based size-exclusion chromatography. Here, we compare the impact of culture methods and purification strategies on small extracellular vesicle, exomere, and supermere cargo. Proteomic analyses show consistently distinct profiles for extracellular vesicles, exomeres, and supermeres regardless of culture conditions or isolation method. In contrast, these two variables influence small RNAs, their base modifications, and lipidomic profiles. We present an online tool to query these and future secretome datasets (https://superomics.shinyapps.io/browse).

Humans↗
PubMed2002

Processing of 3'-extended read-through transcripts by the exosome can generate functional mRNAs.

Strains carrying rna14.1 and rna15.2 mutations are defective in pre-mRNA 3' cleavage, polyadenylation, and transcription termination. Long extended read-through transcripts generated in rna14.1 and rna15.2 strains are greatly stabilized by depletion of Rrp41p, a core component of the exosome complex or the RNA helicase Dob1p/Mtr4p. The absence of the nuclear-specific exosome component, Rrp6p, from the rna14.1 strain gave a very different phenotype. Short polyadenylated pre-mRNAs were strongly stabilized, and these were functional for translation. Production of these mRNAs was suppressed by depletion of Rrp41p, indicating that they are the products of exosome processing followed by uncoupled polyadenylation. The balance between complete degradation of 3'-unprocessed pre-mRNAs and their processing to functional mRNAs is regulated, with degradation favored on glucose media.

3' Untranslated Regions↗
PubMed2006

Structural and biochemical characterization of the yeast exosome component Rrp40.

The exosome is a protein complex that is important in both degradation and 3'-processing of eukaryotic RNAs. We present the crystal structure of the Rrp40 exosome subunit from Saccharomyces cerevisiae at a resolution of 2.2 A. The structure comprises an S1 domain and an unusual KH (K homology) domain. Close packing of the S1 and KH domains is stabilized by a GxNG sequence, which is uniquely conserved in exosome KH domains. Nuclear magnetic resonance data reveal the presence of a manganese-binding site at the interface of the two domains. Isothermal titration calorimetry shows that Rrp40 and archaeal Rrp4 alone have very low intrinsic affinity for RNA. The affinity of an archaeal core exosome for RNA is significantly increased in the presence of the S1-KH subunit Rrp4, indicating that multiple subunits might contribute to cooperative binding of RNA substrates by the exosome.

Amino Acid Motifs↗
PubMed2002

The yin and yang of the exosome.

Recent studies of the eukaryotic ribosomal RNA processing pathway have identified a complex of ten riboexonucleases called the exosome that plays a central role in the precise formation of the 3' ends of several types of RNAs. The exosome also destroys excess ribosomal RNA precursors and unused intermediates and degrades poly(A)-mRNAs in the cytoplasm. In the nucleus, the complex appears to function in a regulated mRNA surveillance system that degrades transcripts in response to defects in the mRNA processing and export pathways. How the cell regulates the nucleolytic prowess of the exosome to ensure correct and timely synthesis and destruction of RNAs is a central focus of current research.

Animals↗
PubMed2005

The Pyrococcus exosome complex: structural and functional characterization.

The exosome is a conserved eukaryotic enzymatic complex that plays an essential role in many pathways of RNA processing and degradation. Here, we describe the structural characterization of the predicted archaeal exosome in solution using small angle x-ray scattering. The structure model calculated from the small angle x-ray scattering pattern provides an indication of the existence of a disk-shaped structure, corresponding to the "RNases PH ring" complex formed by the proteins aRrp41 and aRrp42. The RNases PH ring complex corresponds to the core of the exosome, binds RNA, and has phosphorolytic and polymerization activities. Three additional molecules of the RNA-binding protein aRrp4 are attached to the core as extended and flexible arms that may direct the substrates to the active sites of the exosome. In the presence of aRrp4, the activity of the core complex is enhanced, suggesting a regulatory role for this protein. The results shown here also indicate the participation of the exosome in RNA metabolism in Archaea, as was established in Eukarya.

Archaeal Proteins↗
PubMed2005

Processing the message: structural insights into capping and decapping mRNA.

The 5' m7GpppN cap plays an essential role in the life cycle of eukaryotic mRNA and is required for efficient pre-mRNA splicing, export, stability and translation. Nascent pre-mRNA is capped through a series of three enzymatic steps that result in a 5' N7-methyl guanosine linked by an inverted 5'-5' triphosphate bridge to the first nucleotide of the transcript. Early structural studies revealed the mechanisms employed in the first two steps of capping, and more recent structural studies have completed the suite of capping activities and shed light on the mechanisms that target the capping apparatus to the phosphorylated C-terminal domain of RNA polymerase II. RNA decay pathways also target the RNA cap structure. After deadenylation of polyadenylated mRNA, enzymes of the 5'-3' decay pathway hydrolyze the mRNA cap to expose the 5' RNA end to 5'-3' exoribonuclease activities. In the 3'-5' decay pathway, exosome-mediated degradation of RNA occurs from the 3' end after deadenylation, ultimately generating a cap structure that is hydrolyzed by enzymes of this pathway. Recent structural studies have illuminated the mechanisms employed for decapping mRNA in both 5'-3' and 3'-5' decay pathways.

Acid Anhydride Hydrolases↗
PubMed2002

CML28 is a broadly immunogenic antigen, which is overexpressed in tumor cells.

Donor lymphocyte infusion (DLI) reliably induces durable remission in 75-80% of patients with relapsed chronic myelogenous leukemia (CML) after allogeneic hematopoietic stem cell transplantation. To identify immunological targets of the graft-versus-leukemia response (GVL) after DLI, we used CML post-DLI responder sera to screen a CML cDNA expression library. One of the antigens identified in this screen is a M(r) 28,000 protein, termed CML28. CML28 is identical to hRrp46p, a component of the human exosome, a multiprotein complex involved in the 3' processing of RNA. Components of the human exosome include known autoantigens, such as PMScl-100, an autoantibody target in patients with polymyositis, scleroderma, or polymyositis-scleroderma overlap syndrome. Recombinant CML28-GST fusion protein was purified, and used in Western blot and ELISA to demonstrate the development of a high-titer CML28-specific IgG antibody response in a patient with relapsed CML who responded to DLI. Northern blotting demonstrated that CML28 is highly expressed in a variety of hematopoietic and epithelial tumor cell lines, but not in normal hematopoietic tissues or other normal tissue, with the exception of testis. Purified recombinant CML28 was used to generate a CML28-specific murine monoclonal antibody. Western blotting with CML28 monoclonal antibody against whole-cell lysates derived from blood and marrow of normal donors and patients with leukemia revealed high expression of this antigen in tumor but not in normal samples. Because CML28 was highly expressed in epithelial tumor cell lines, anti-CML28 responses were also examined in patients with solid tumors. By ELISA, we found specific serological responses in 10-33% of patients with lung cancer, melanoma, and prostate cancer. Our studies suggest that immunogenicity of CML28 is likely because of overexpression of this antigen in tumor cells. Moreover, given its expression and immunogenicity in a wide variety of malignancies, CML28 merits additional evaluation as a target for antigen-specific immunotherapy.

Antibodies, Neoplasm↗
PubMed2003

An exosome-like complex in Sulfolobus solfataricus.

We present the first experimental evidence for the existence of an exosome-like protein complex in Archaea. In Eukarya, the exosome is essential for many pathways of RNA processing and degradation. Co-immunoprecipitation with antibodies directed against the previously predicted Sulfolobus solfataricus orthologue of the exosome subunit ribosomal-RNA-processing protein 41 (Rrp41) led to the purification of a 250-kDa protein complex from S. solfataricus. Approximately half of the complex cosediments with ribosomal subunits. It comprises four previously predicted orthologues of the core exosome subunits from yeast (Rrp41, Rrp42, Rrp4 and Csl4 (cepl synthetic lethality 4; an RNA-binding protein and exosome sub-unit)), whereas other predicted subunits were not found. Surprisingly, the archaeal homologue of the bacterial DNA primase DnaG was tightly associated with the complex. This suggests an RNA-related function for the archaeal DnaG-like proteins. Comparison of experimental data from different organisms shows that the minimal core of the exosome consists of at least one phosphate-dependent ribonuclease PH homologue, and of Rrp4 and Csl4. Such a protein complex was probably present in the last common ancestor of Archaea and Eukarya.

Macromolecular Substances↗
PubMed2001

The exosome of Trypanosoma brucei.

The yeast exosome is a complex of at least 10 essential 3'-5' riboexonucleases which is involved in 3'-processing of many RNA species. An exosome-like complex has been found or predicted to exist in other eukaryotes but not in Escherichia coli. The unicellular parasite Trypanosoma brucei diverged very early in eukaryotic evolution. We show here that T.brucei contains at least eight exosome subunit homologs, but only a subset of these associate in a complex. Accordingly, the T.brucei exosome is smaller than that of yeast. Both free and complex-associated homologs are essential for cell viability and are involved in 5.8S rRNA maturation. We suggest that the exosome was present in primitive eukaryotes, and became increasingly complex during subsequent evolution.

Alleles↗