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At least 163 records · Page 9Linked to original sources
PubMed2001

Mutation analyses of 268 candidate genes in human tumor cell lines.

We have performed a homozygous deletion screen on 268 candidate genes in 90 human tumor cell lines derived from multiple types of cancers. Most of the candidate genes investigated have been proposed to be involved in cellular processes that are germane to cancer progression, such as cell cycle control, genome maintenance, chromatin remodeling, cell adhesion, and apoptosis. We have detected novel homozygous deletions affecting four independent loci: Brahma-related gene (SMARCA4) on chromosome 19p in the TSU-Pr1 prostate and A427 lung carcinoma lines, Map Kinase Kinase 3 (MAP2K3) on 17q in the NCI-H774 lung tumor cell line, TMPRSS2 on 21q in the Bx PC-3 pancreatic carcinoma line, and Cadherin 6 (CDH6) on 5p in the SK-LU-1 lung carcinoma line. Subsequent analyses of the coding sequences of these four genes using cDNAs from a panel of tumor cell lines revealed multiple sequence variants. The results of this mutation study serve to demonstrate the feasibility of performing high-throughput screens of candidate genes in tumor cell lines to identify genes that may be targeted for mutation during the development of cancer.

Cadherins↗
PubMed2000

Bioreactor-scale production and one-step purification of Epstein-Barr nuclear antigen 1 expressed in baculovirus-infected insect cells.

Epstein-Barr virus (EBV)-encoded nuclear antigen 1 (EBNA1) is expressed in all EBV-associated malignancies and is essential for EBV-genome maintenance. Antibodies to EBNA1 are abundantly detected in serum of most EBV carriers but EBNA1 escapes recognition by effector T-lymphocytes. To further study the functional and immunological characteristics of EBNA1 it is important to have sufficient quantities of purified EBNA1 available. This paper describes a simple, reproducible method for the production and purification of EBV-encoded EBNA1 expressed in insect cells (bEBNA1). For quantification of EBNA1 expression levels in cell lines and for monitoring bEBNA1 purification and overall yields we developed a quantitative and EBNA1-specific capture ELISA. We observed that EBV-positive cell lines express EBNA1 at different levels, with the B cell lymphoblastoid cell line X50/7 having the highest production. However, much larger quantities (380-fold) were obtained by expressing bEBNA1 in recombinant-baculovirus-infected Sf9 insect cells. Scaling-up experiments revealed that bEBNA1 expression kinetics and protein stability are identical in 1-liter stirred bioreactors when compared to expression in stationary culture flasks. Optimal expression was reached after 72 h following inoculation at 1 pfu/cell, when insect cell viability was about 50%. For purification the nuclear fraction containing most of the bEBNA1 (>95%) was isolated. Solubilized bEBNA1 was purified by a one-step oriP DNA-Sepharose affinity purification procedure, using biotinylated PCR-amplified family of repeats (FR)-domain products immobilized onto streptavidin agarose. A >200-fold specific enrichment was reached and yields of bEBNA1 with an estimated purity of >95%.

Animals↗
PubMed1995

Antigenic and sequence variation in the C-terminal unique domain of the Epstein-Barr virus nuclear antigen EBNA-1.

The Epstein-Barr virus (EBV) nuclear antigen EBNA-1 is essential for viral genome maintenance in vitro and may be the only EBV protein expressed by the majority of latently infected cells in vivo. EBNA-1 may therefore be critical to the evasion of host immunity which allows persistent infection. EBNA-1 includes a polymorphic internal repeat domain of unknown significance and unique regions which mediate all known functional activities and which have hitherto been assumed to be conserved between strains. Monoclonal antibodies were generated using a construct based on EBNA-1 of the prototype B95-8 strain, deleted for the repeat domain. These antibodies showed a limited profile of recognition of EBNA-1 in common laboratory EBV+ cell lines by immunoprecipitation and immunostaining. The observed antigenic heterogeneity also extended to spontaneously transformed B lymphoblastoid cell lines (LCLs) representing viral isolates circulating within US and UK populations. DNA fragments spanning the C-terminal unique domain of EBNA-1 from eleven spontaneous LCLs were amplified by polymerase chain reaction for sequencing, which directly demonstrated extensive and unexpected variability between diverse type 1 EBV isolates. The resulting polymorphism affects most of the putative MHC Class I binding epitopes which could be identified within this region using published sequence motifs, and influences MHC binding by variants of at least one such peptide in the processing mutant cell line T2. These findings could be related to the apparent lack of recognition of EBNA-1 by cytotoxic T lymphocytes.

Amino Acid Sequence↗
PubMed2002

Strategies for the identification and analysis of viral immune-evasive genes--cytomegalovirus as an example.

Co-evolution of herpesviruses with their hosts has resulted in multiple interactions between viral genes and cellular functions. Some interactions control genomic maintenance and replication in specific tissues, other affect the immune control at various stages. Few immunomodulatory functions of genes can be predicted by sequence homology. The majority of genes with immunomodulatory properties only become apparent in functional assays. This chapter reviews procedures which have been used for successful identification of immunomodulatory genes in the past and deals with recent methods which may be applicable for the identification of additional immunomodulatory functions unknown so far.

Animals↗
PubMed1996

A vital function for mitochondrial DNA in the petite-negative yeast Kluyveromyces lactis.

Petite-negative yeasts do not form viable respiratory-deficient mutants on treatment with DNA-targeting drugs that readily eliminate the mitochondrial DNA (mtDNA) from petite-positive yeasts. However, in the petite-negative yeast Kluyveromyces lactis, specific mutations in the nuclear genes MG12 and MG15 encoding the alpha- and gamma-subunits of the mitochondrial F1-ATPase, allow mtDNA to be lost. In this study we show that wild-type K. lactis does not survive in the absence of its mitochondrial genome and that the function of mgi mutations is to suppress lethality caused by loss of mtDNA. Firstly, we find that loss of a multicopy plasmid bearing a mgi allele readily occurs from a wild-type strain with functional mtDNA but is not tolerated in the absence of mtDNA. Secondly, we cloned the K. lactis homologue of the Saccharomyces cerevisiae mitochondrial genome maintenance gene MGM101, and disrupted one of the two copies in a diploid. Following sporulation, we find that segregants containing the disrupted gene form minicolonies containing 6-8000 inviable cells. By contrast, disruption of MGM101 is not lethal in a haploid mgi strain with a specific mutation in a subunit of the mitochondrial F1-ATPase. These observations suggest that mtDNA in K. lactis encodes a vital function which may reside in one of the three mitochondrially encoded subunits of Fo.

Amino Acid Sequence↗
PubMed2026

The TyrRS cascade: circadian gating of neuronal DNA repair and its collapse in aging.

Age-related neurodegenerative diseases are characterized by progressive DNA damage in post-mitotic neurons against a backdrop of deteriorating circadian rhythms, yet the molecular link between these conjoined features of brain aging remains unclear. We propose the TyrRS cascade as that link: a signaling architecture in which the noncanonical nuclear functions of tyrosyl-tRNA synthetase (TyrRS/YARS1) schedule neuronal genome maintenance across the day through three coregulated streams, PARP1-mediated damage sensing, TRIM28/NuRD heterochromatin maintenance, and LIN9/DREAM control of a 67-gene repair archive. The model's central commitment is that the operative variable is oscillation amplitude rather than mean activity. We argue that as serum tyrosine rises with age and circadian amplitude flattens, these insults compound into a double-hit collapse that traps the cascade in a frozen-intermediate state, which bulk-tissue assays misread as elevated mean activity when the oscillation has merely lost its excursion. Placed in dialogue with oscillatory-clearance models of sleep, the cascade and the glymphatic system emerge as complementary, compartment-separated arms of a single sleep-dependent maintenance program that fail together through amplitude collapse, yielding a signature of preserved phase architecture with reduced dynamic range. Reframing neurodegeneration as a scheduling failure rather than a capacity failure carries three translational consequences: Pulsatile, phase-aligned dosing should outperform sustained-release pharmacology, which is predicted to flatten the rhythm it aims to restore; demonstrating target engagement will require phase-resolved rather than single-timepoint measurement; and because both arms fail together, combined restoration of intracellular repair and extracellular clearance should outperform single-arm intervention.

Alzheimer’s disease↗
PubMed2026

The 1H, 15N and 13C backbone resonance assignments of an intrinsically disordered region (467-696) of breast cancer type 1 susceptibility protein (BRCA1).

The tumor suppressor protein breast cancer type 1 susceptibility protein (BRCA1) plays a central role in maintaining genome stability through its involvement in DNA damage repair, transcriptional regulation, and cell-cycle control. BRCA1 functions as an obligate heterodimer with its binding partner, the BRCA1-associated RING domain protein 1 (BARD1), to coordinate accurate DNA repair. While the structured N- and C-terminal domains of BRCA1 have been well-characterized, the large central region encoded largely by exon 11 that comprises ~ 80% of the protein, is intrinsically disordered, and remains poorly structurally characterized. This intrinsically disordered region (IDR) harbors critical interaction interfaces for key proteins involved in genome maintenance, including RAD50, RAD51, MYC, and RB. Here, we report the backbone resonance assignments of a BRCA1 IDR construct spanning residues 467-696, providing a foundation for future studies aimed at understanding how the disordered central region of BRCA1 contributes to homologous recombination, interactions with BARD1, and overall BRCA1 tumor suppressor function.

BRCA1 Protein↗
PubMed2005

Gene expression and DNA repair in progeroid syndromes and human aging.

Human progeroid syndromes are caused by mutations in single genes accelerating some but not all features of normal aging. Most progeroid disorders are linked to defects in genome maintenance, and while it remains unknown if similar processes underlie normal and premature aging, they provide useful models for the study of aging. Altered transcription is speculated to play a causative role in aging, and is involved in the pathology of most if not all progeroid syndromes. Previous studies demonstrate that there is a similar pattern of gene expression changes in primary cells from old and Werner syndrome compared to young suggesting a presence of common cellular aging mechanisms in old and progeria. Here we review the role of transcription in progeroid syndromes and discuss the implications of similar transcription aberrations in normal and premature aging.

Aging↗
PubMed2026

Decoding SUMOylation as a metabolic stress sensor in aging and age-related disorders: Mechanisms, tissue specificity and therapeutic potential.

SUMOylation is a reversible post-translational modification increasingly recognized for its role in coordinating cellular responses to metabolic stress during aging. Emerging evidence indicates that it functions beyond a conventional modification, representing an adaptive stress‑responsive regulatory network that integrates metabolic, oxidative, inflammatory, and proteotoxic signals. Rather than acting on isolated pathways, this network finely tunes mitochondrial function, proteostasis, genome maintenance, immune balance, and epigenetic regulation. Accumulating evidence indicates that SUMO-dependent regulation exhibits remarkable tissue specificity, supporting mitochondrial adaptation and contractile integrity in skeletal muscle, shaping lipid and glucose metabolism in the liver, modulating proteotoxic stress and neuronal resilience in the brain, and contributing to immune cell differentiation and chronic low-grade inflammation during aging. In this review, we summarize current mechanistic insights into SUMO signaling across aging-relevant tissues, with particular emphasis on its functional interplay with other post-translational modifications, including ubiquitination and acetylation. We discuss how SUMOylation operates as a shared regulatory layer while enabling context-dependent outcomes that underlie diverse aging phenotypes and age-related disorders. Finally, we evaluate emerging translational approaches-ranging from pharmacological modulation of SUMO enzymes to lifestyle interventions such as caloric restriction and exercise-that highlight both the opportunities and challenges of targeting SUMO-regulated stress responses in aging. Together, this synthesis provides a framework for understanding how SUMOylation links metabolic stress to tissue-specific aging trajectories and therapeutic potential.

Aging↗
PubMed2026

CARM1 in human cancer: a multifunctional epigenetic node driving tumor plasticity and therapeutic vulnerability.

Coactivator-associated arginine methyltransferase 1 (CARM1/PRMT4) is a signal-responsive epigenetic regulator that couples oncogenic and stress signals to chromatin, transcription, RNA processing, metabolism, and genome maintenance. Its effects arise from both asymmetric arginine methylation of histone and non-histone substrates and methyltransferase-independent scaffolding activities. This review critically synthesizes the structural basis, substrate networks, methylarginine readers, and cancer-contextual functions of CARM1. We propose that its apparently opposing oncogenic and tumor-suppressive activities are determined by lineage-specific substrates, regulatory post-translational modifications, cofactor and chromatin availability, and stage- or microenvironment-dependent stress signals. We further evaluate CARM1-directed therapy using an evidence-graded framework. Catalytic inhibitors such as TP-064 and EZM2302 differ in binding mode and substrate coverage, whereas emerging degraders can remove scaffolding functions but remain constrained by delivery, E3-ligase heterogeneity, pharmacokinetics, and therapeutic-window uncertainties. Biomarker-guided synthetic-lethal and immunotherapy combinations may therefore offer the most tractable route to clinical translation. This framework positions CARM1 as a context-conditioned signal-to-chromatin translator rather than a uniformly druggable oncogene.

Humans↗
PubMed2026

Cancer stemness-modulating (CSM) proteins in pan-cancer chemoresistance: regulatory roles and mechanisms.

Cancer stemness is a property of cancer cells that plays critical roles in tumorigenesis and therapeutic resistance. We previously identified and categorized, based on literature evidence, a group of fourteen cancer stemness-modulating (CSM) circular RNAs (circRNAs) in colorectal cancer (CRC), which we termed CSM-circRNAs. In the present work, we show that the proteins regulated by these CRC CSM-circRNAs, with one exception for which information is currently unavailable, are bona fide modulators of cancer stemness across a wide range of cancer types. We, therefore, designate these proteins as CSM-proteins. As chemoresistance is a major trait of cancer stemness, we further investigated the molecular mechanisms through which CSM-proteins contribute to chemoresistance. Our analysis reveals that twelve CRC CSM-proteins are implicated in chemoresistance across fourteen cancer types and resistance to ten therapeutic agents. Nine distinct chemoresistance mechanisms are identified and organized into five broader functional axes: survival, drug processing, genome maintenance, plasticity and adaptation, leading us to propose an integrated mechanistic framework for CSM-protein-mediated chemoresistance. Most CSM-proteins operate across multiple functional axes in different cancer contexts, with survival-associated mechanisms, particularly apoptosis evasion, and epithelial-mesenchymal transition-associated plasticity emerging as the predominant modes of chemoresistance. Furthermore, transcriptional regulatory CSM-proteins exhibit broader mechanistic profiles than other molecular categories, although the strength and extent of evidence vary across proteins and cancer types. Taken together, the proposed CSM-protein pan-cancer chemoresistance framework offers a biologically and therapeutically relevant regulatory network for understanding the mechanisms underlying cancer chemoresistance based predominantly on preclinical evidence. Our findings may provide a preclinical conceptual foundation for the development of combinatorial therapeutic strategies targeting cancer stemness and chemoresistance through the CSM-circRNA-CSM-protein regulatory axis.

Cancer stemness↗
PubMed2005

BRCA1 regulation of transcription.

BRCA1, a tumor suppressor gene on chromosome 17q21, was identified in 1994 based on its linkage to hereditary breast and ovarian cancer syndromes. The BRCA1 gene encodes a 220 kDa nuclear phosphoprotein. Studies aimed at elucidating the mechanisms of its tumor suppressor activity have revealed, in part, that BRCA1 participates in the DNA damage response and acts to maintain the integrity of the genome. This activity is generic and does not account for the propensity of BRCA1 mutation carriers to develop specific tumor types rather than a broad spectrum of cancers. In addition to genome maintenance, BRCA1 has been found to broadly regulate gene transcription, even though it is not itself a sequence-specific DNA-binding transcription factor. The ability of BRCA1 to function as a coregulator of transcription may underlie some of its tumor suppressor activity and may explain the tissue-specific nature of this activity. This review will focus on how BRCA1 selectively regulates transcription and how this regulatory function may relate to tumor suppression.

Animals↗
PubMed2026

Slow PPi release enhances fidelity of the SARS-CoV-2 RNA dependent RNA polymerase.

Viral RNA-dependent RNA polymerases (RdRps) must balance replication speed with fidelity, preserving genome integrity while permitting enough variability for viral adaptation. The SARS-CoV-2 RdRp complex (non-structural protein 12/7/8) achieves this through the interplay of its intrinsic replication fidelity and a potential proofreading exonuclease complex (NSP10/14). Here, we comprehensively quantify the intrinsic fidelity of the SARS-CoV-2 RdRp through direct pre-steady-state kinetic analyses of nucleotide incorporation across all possible templating bases paired with incoming nucleotides. We discovered substantial variation in discrimination against mismatches ranging from one error in 103 to 108 (median of 105). Crucially, our data reveal a slow pyrophosphate release step that significantly enhances fidelity by effectively introducing a kinetic checkpoint after nucleotide incorporation. The error rates we measured for the RdRp align closely with observed in vivo mutation rates, suggesting that the exonuclease complex may play a less critical role than previously assumed in correcting mistakes during polymerization. These insights advance our understanding of SARS-CoV-2 replication fidelity, and the role of various subcomplexes in genome maintenance and adaptation.

SARS-CoV-2↗
PubMed2026

Comprehensive profiling of antibiotic resistance genes and functional clusters of orthologous groups annotation of gut microbiota in Indonesian Kedu chickens.

Antibiotic resistance is a growing global health concern, with poultry systems acting as important reservoirs of antibiotic resistance genes (ARGs). However, resistome and functional profiles of indigenous chickens raised under traditional systems remain underexplored. This study aimed to characterize the antibiotic resistome, virulence factor genes, and metabolic potential of gut microbiota in Indonesian Kedu chickens using a shotgun metagenomic approach. Digesta samples from five gastrointestinal segments of 21 healthy adult chickens were analyzed through high-throughput sequencing. ARGs were identified using the Comprehensive Antibiotic Resistance Database (CARD) and Antibiotic Resistance Genes Databases (ARDB), while virulence factors and functional genes were annotated using Virulence Factor Database (VFDB), Clusters of Orthologous Groups (COG), and Carbohydrate-Active EnZymes (CAZy) databases. Results revealed a diverse resistome dominated by multidrug resistance and efflux pump mechanisms, with prominent genes associated with fluoroquinolone, tetracycline, β-lactam, and glycopeptide resistance. The detection of clinically relevant ARGs suggests that genetic determinants associated with antimicrobial resistance are present in the gut microbiota of traditionally raised Kedu chickens, although metagenomic data alone cannot determine whether these genes are actively expressed or confer phenotypic resistance. Virulence factor analysis showed functions related to adherence, immune evasion, iron acquisition, quorum sensing, and efflux activity, reflecting strong microbial adaptability. Functional profiling demonstrated enrichment in translation, carbohydrate and amino acid metabolism, genome maintenance, and cell envelope biogenesis. Additionally, CAZyme analysis indicated a high capacity for complex polysaccharide degradation, supporting efficient utilization of fiber-rich traditional diets. In conclusion, this study provides a comprehensive metagenomic overview of antibiotic resistance and functional potential in Kedu chicken gut microbiota, emphasizing the importance of incorporating indigenous poultry into antimicrobial resistance surveillance within a One Health framework.

Antibiotic resistance genes↗
PubMed2004

Trypanosoma cruzi contains a single detectable uracil-DNA glycosylase and repairs uracil exclusively via short patch base excision repair.

Enzymes involved in genomic maintenance of human parasites are attractive targets for parasite-specific drugs. The parasitic protozoan Trypanosoma cruzi contains at least two enzymes involved in the protection against potentially mutagenic uracil, a deoxyuridine triphosphate nucleotidohydrolase (dUTPase) and a uracil-DNA glycosylase belonging to the highly conserved UNG-family. Uracil-DNA glycosylase activities excise uracil from DNA and initiate a multistep base-excision repair (BER) pathway to restore the correct nucleotide sequence. Here we report the biochemical characterisation of T.cruzi UNG (TcUNG) and its contribution to the total uracil repair activity in T.cruzi. TcUNG is shown to be the major uracil-DNA glycosylase in T.cruzi. The purified recombinant TcUNG exhibits substrate preference for removal of uracil in the order ssU>U:G>U:A, and has no associated thymine-DNA glycosylase activity. T.cruzi apparently repairs U:G DNA substrate exclusively via short-patch BER, but the DNA polymerase involved surprisingly displays a vertebrate POLdelta-like pattern of inhibition. Back-up UDG activities such as SMUG, TDG and MBD4 were not found, underlying the importance of the TcUNG enzyme in protection against uracil in DNA and as a potential target for drug therapy.

Amino Acid Sequence↗
PubMed2006

Chronic exposure to sublethal doses of radiation mimetic Zeocin selects for clones deficient in homologous recombination.

DNA double-strand breaks (DSBs) are highly toxic lesions leading to genome variability/instability. The balance between homologous recombination (HR) and non-homologous end-joining (NHEJ), two alternative DSB repair systems, is essential to ensure genome maintenance in mammalian cells. Here, we transfected CHO hamster cells with the pcDNA3.1/Zeo plasmid, and selected transfectants with Zeocin, a bleomycin analog which produces DSBs. Despite the presence of a Zeocin resistance gene in pcDNA3.1/Zeo, Zeocin induced 8-10 gamma-H2AX foci per cell. This shows that the Zeocin resistance gene failed to fully detoxify cells treated with Zeocin, and that during selection cells were submitted to a chronic sublethal DSB stress. Selected clones show decreases in both spontaneous and induced intrachromosomal HR. In contrast, in an in vitro assay, these clones show an increase in NHEJ products specific to the KU86 pathway. We selected cells, in the absence of pcDNA3.1/Zeo, with low and sublethal doses of Zeocin, producing a mean 8-10 gamma-H2AX foci per cell. Newly selected clones exhibited similar phenotypes: HR decrease accompanied by an increase in KU86-dependent NHEJ efficiency. Thus chronic exposure to sublethal numbers of DSBs selects cells whose HR versus NHEJ balance is altered. This may well have implications for radio- and chemotherapy, and for management of environmental hazards.

Animals↗
PubMed2005

Conferring substrate specificity to DNA helicases: role of the RecQ HRDC domain.

RecQ DNA helicases are multidomain enzymes that play pivotal roles in genome maintenance pathways. While the ATPase and helicase activities of these enzymes can be attributed to the conserved catalytic core domain, the role of the Helicase-and-RNase-D-C-terminal (HRDC) domain in RecQ function has yet to be elucidated. Here, we report the crystal structure of the E. coli RecQ HRDC domain, revealing a globular fold that resembles known DNA binding domains. We show that this domain preferentially binds single-stranded DNA and identify its DNA binding surface. HRDC domain mutations in full-length RecQ lead to surprising differences in its structure-specific DNA binding properties. These data support a model in which naturally occurring variations in DNA binding residues among diverse RecQ homologs serve to target these enzymes to distinct substrates and provide insight into a mechanism whereby RecQ enzymes have evolved distinct functions in organisms that encode multiple recQ genes.

Amino Acid Sequence↗
PubMed2006

Molecular basis for phosphorylation-dependent, PEST-mediated protein turnover.

Proteasomal-mediated rapid turnover of proteins is often modulated by phosphorylation of PEST sequences. The E2 protein from papillomavirus participates in gene transcription, DNA replication, and episomal genome maintenance. Phosphorylation of a PEST sequence located in a flexible region accelerates its degradation. NMR analysis of a 29 amino acid peptide fragment derived from this region shows pH-dependent polyproline II and alpha helix structures, connected by a turn. Phosphorylation, in particular that at serine 301, disrupts the overall structure, and point mutations have either stabilizing or destabilizing effects. There is an excellent correlation between the thermodynamic stability of different peptides and the half-life of E2 proteins containing the same mutations in vivo. The structure around the PEST region appears to have evolved a marginal stability that is finely tunable by phosphorylation. Thus, conformational stability, rather than recognition of a phosphate modification, modulates the degradation of this PEST sequence by the proteasome machinery.

Amino Acid Motifs↗