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Fluorescent reporter assay reveals ribonucleotides promote mismatch correction in vivo.

Ribonucleotides can serve as a strand discrimination signal in reconstituted in vitro biochemical mismatch repair (MMR) assays, but the influence of ribonucleotides on mismatch correction has not been measured directly in vivo. We have developed a fluorescence-based host cell reactivation assay that reports correction of a mismatch in proximity of a site-specifically incorporated ribonucleotide. A ribonucleotide leads to enhanced mismatch correction. While neither inactivation of a single allele nor knockdown of RNaseH2 is sufficient to suppress ribonucleotide directed MMR, a modest but statistically significant impairment for repair of mismatches in the presence of an embedded ribonucleotide is observed in RNaseH2 knockout cell lines. Reporter plasmids with ribonucleotides located in either the 3' or 5' orientation are robustly repaired in MMR-proficient cells but are weakly repaired in MMR-deficient cells, underscoring their utility as effective MMR reporters. Significant ribonucleotide-enhanced mismatch correction was consistently observed in MMR-deficient cells when the ribonucleotide is in the 3' orientation. The presence of a ribonucleotide led to enhanced MMR even in RNaseH2 knockout cells, suggesting that other enzymes may promote ribonucleotide-directed MMR. Loss of RNaseH2 was not sufficient to confer significant resistance to the alkylating agent, temozolomide, in support of a model in which ribonucleotide-directed repair events make minor contributions to the canonical MMR pathway in mammalian cells. We propose a model in which MMR-independent ribonucleotide enhanced correction of mismatches can proceed by ribonucleotide excision repair when the ribonucleotide is in the 5' direction, and proceeds by an unknown mechanism when the ribonucleotide is in the 3' direction.

DNA Mismatch Repair

Luciferase-Based Reporter Assay for the Assessment of Aurora A-Kinase Activity in Mitotic Cycle.

Luciferase-based reporter assay is an important tool that employs bioluminescence to quickly and precisely investigate the gene of interest's promoter activity by reporter gene expression at the transcriptional level. The promoter of the gene of interest is fused with the reporter gene (a gene that produces luciferase enzymes) and then transfected into the cells. Luciferase is an enzyme that catalyzes a chemical reaction to produce light. The bioluminescence activity of the luciferase gene in the transfected cells is directly proportional to the expression of the gene of interest, which is measured by using a luminometer. In this chapter, we outline the use of a dual-reporter luciferase assay to measure Aurora A kinase activity during the mitotic cycle.

Genes, Reporter

Interrogation of functional variants in COPD GWAS loci by massively parallel reporter assays.

RATIONALE: Genome-wide association study (GWAS) loci often contain many linked variants, making it difficult to determine which variant is functionally relevant. Massively parallel reporter assays (MPRA) allow experimental testing of candidate variants to identify those with regulatory activity. Prior chronic obstructive pulmonary disease (COPD) MPRA studies have largely focused on individual loci, whereas broader multi-locus, multi-cell-type interrogation remains limited. OBJECTIVES: We aim to identify functional variants in five COPD GWAS loci across three lung-relevant cell types. METHODS: We screened 1120 variants using MPRA in epithelial (16HBE), fibroblast (MRC5), and endothelial (HUVEC) cells followed by reporter assay validation. Public Hi-C, ChIP-seq and ATAC-seq datasets were analyzed to evaluate chromatin context near candidate variants. We further performed CRISPR interference (CRISPRi) targeting variant-containing regions and measured gene expression by RT-qPCR in primary normal human bronchial epithelial (NHBE) cells using two gRNAs per variant. Co-immunoprecipitation was performed to test interaction between selected candidate genes. MEASUREMENTS AND MAIN RESULTS: In MPRA, we identified 25 variants with allele-specific effects (∼2% of tested variants). Enrichment of H3K27Ac and open chromatin near rs35421223 was detected in 16HBE cells. CRISPRi identified two SNP-gene pairs, RUVBL1 and RAB7A regulated by rs35421223 in both the 16HBE cell line and primary NHBE cells. We detected interaction between RUVBL1 and the known COPD gene product FAM13A. CONCLUSIONS: Screening COPD loci across three cell types identified functional regulatory variants and linked them to candidate target genes for future mechanistic studies.

Journal Article

Establishment of a STAT6 Reporter Assay for Screening Environmental Toxicants Affecting Allergic Airway Inflammation.

Air pollution-associated allergic airway inflammation is an increasing public health concern. Interleukin‑4 (IL‑4) and interleukin‑13 (IL‑13), which activate the Signal Transducer and Activator of Transcription 6 (STAT6) pathway, a central mediator of allergic airway inflammation, may modulate the respiratory toxicities of pollutants. The present study describes the generation and validation of a stable STAT6 luciferase reporter assay in human airway epithelial cells for evaluating environmental toxicants that modulate STAT6 signaling. Human bronchial epithelial 16HBE14o- cells were transduced with a STAT6-responsive luciferase reporter using a lentiviral vector, followed by optimization of puromycin selection and multiplicity of infection, and monoclonal isolation by limiting dilution. A stable clone with strong and reproducible induction across serial passages was selected. Reporter responsiveness was validated by IL-4/IL-13 stimulation, and STAT6 dependence was confirmed using selective STAT6, STAT5, and STAT3 inhibitors. Assay performance was quantified by Z'-factor analysis, which indicated reproducible signal separation. Furthermore, the assay was applied to individual air-pollution constituents, and benzo[b]fluoranthene and particulate matter significantly increased STAT6 reporter activity. This method provides a scalable approach for measuring STAT6 activity in airway epithelial cells and for prioritizing environmental toxicants that modulate allergic airway signaling.

STAT6 Transcription Factor

Uniform processing and analysis of IGVF massively parallel reporter assay data with MPRAsnakeflow.

As researchers and clinicians seek to identify human genomic alterations relevant to traits and disorders, identifying and aggregating evidence providing mechanistic support for associations between alterations and phenotypes remains challenging. In particular, the study of noncoding genomic variation remains a major challenge because of the lack of accurate functional annotation for activity in a given context and across alleles. Experimental evidence is critical for prioritizing and interpreting functional effects of genetic alterations. Massively parallel reporter assays (MPRAs) have emerged as a powerful high-throughput approach, enabling quantification of regulatory element activity and allelic effects, as well as systematic dissection of gene regulatory logic and variant effects across different contexts. However, the diversity of MPRA designs, lack of standardized formats, and many potential processing parameters hamper data integration, reproducibility, and meta-analyses across studies. To address these challenges, the Impact of Genomic Variation on Function (IGVF) Consortium established an MPRA focus group to develop community standards, including harmonized file formats, and robust analysis pipelines for a wide range of library types and experimental designs. Here, we present these formats and comprehensive computational tools, MPRAlib and MPRAsnakeflow, for uniform processing from raw sequencing reads to counts, processing, and visualization. Using diverse MPRA data sets, we investigated technical variability sources including barcode sequence bias, outlier barcodes, and delivery method (episomal vs. lentiviral). Our results establish best practices for MPRA data generation and analysis, facilitating robust, reproducible research and large-scale integration. The presented tools and standards are publicly available, providing a foundation for future collaborative efforts in regulatory genomics.

Humans

TENT5C functions as a corepressor in the ligand-bound glucocorticoid receptor and estrogen receptor α complexes.

Terminal nucleotidyltransferase 5C (TENT5C) is a noncanonical poly(A) polymerase that promotes cancer suppression. TENT5C has been proposed to mediate the susceptibility of multiple myeloma to treatment with dexamethasone, a steroid hormone analog that binds to the glucocorticoid receptor (GR). However, the relationship between TENT5C and nuclear receptor (NR) signaling remains unclear. In this study, we investigate the regulatory role of TENT5C in the GR and estrogen receptor α (ERα) ligand complexes. We find that TENT5C acts as a corepressor of both GR and ERα. Molecular dynamics simulations indicate that the third TENT5C LXXLL motif directly interacts with ERα, but not GR. The physical interaction of TENT5C and ERα is supported by co-immunoprecipitation assays. Reporter assays show that mutations to the third TENT5C LXXLL motif disrupt TENT5C-mediated repression of ERα but do not affect the repression of the GR complex. In addition, the disruption of TENT5C poly(A) polymerase activity does not appear to affect TENT5C repression of ERα in the cell lines studied. Taken together, our findings highlight a role of TENT5C as an NR corepressor, differentially modulating GR- and ERα-induced transcriptional activity.

Receptors, Glucocorticoid

Comprehensive genomic profiling and tumor mutational burden in parathyroid carcinoma: a nationwide real-world study from Japan.

PURPOSE: Parathyroid carcinoma (PC) is an extremely rare endocrine malignancy with limited treatment options for unresectable or recurrent cases. With the increasing use of comprehensive genomic profiling (CGP), treatment based on genomic findings is becoming more common. However, the frequency and clinical significance of elevated tumor mutational burden (TMB) in PC remain unclear because previous studies have been limited by small sample sizes. METHODS: We retrospectively analyzed genomic and clinical data of patients with PC registered in the Center for Cancer Genomics and Advanced Therapeutics database in Japan between June 2019 and March 2025. TMB values were obtained as reported by each CGP assay. TMB-H was defined as TMB ≥ 10 mut/Mb for descriptive analyses. We also assessed genomic alterations, microsatellite instability (MSI) status, and clinicogenomic characteristics. RESULTS: Twenty-five patients with PC were included. The median assay-reported TMB was 4.0 mut/Mb (range, 0-35). Seven tumors (28.0%) had assay-reported TMB values of ≥ 10 mut/Mb, including three (12.0%) with TMB ≥ 20 mut/Mb. The most frequently altered genes were CDC73 (40%), TP53 (32%), and MEN1 (24%). No co-alterations were observed between CDC73 and MEN1 or between CDC73 and TP53. One tumor was MSI-high and was included in the TMB-H group. POLE alterations were detected in three cases, including two tumors in the TMB-H group. CONCLUSION: This nationwide, real-world study demonstrated that a subset of PCs showed elevated assay-reported TMB values and genomic features potentially related to abnormalities in DNA replication or repair pathways. These findings support the clinical relevance of comprehensive genomic profiling in identifying the molecular heterogeneity and potential therapeutic opportunities for this rare malignancy.

Humans

Screening of Estrogenic and Antiestrogenic Effects of Estradiol, Bisphenol A, and Fulvestrant Using 2D and 3D Breast Cancer Cell Systems With a Luciferase Reporter Gene Assay.

Endocrine-disrupting chemicals (EDCs) like bisphenol A (BPA) pose health risks by interfering with hormones. This study develops and utilizes in vitro 2D and 3D cell models to evaluate the estrogenic and antiestrogenic properties of compounds. Human breast cancer cell lines T47D and MCF7, stably transfected with a luciferase reporter gene (ERE-LUC), were first compared in 2D. Due to the significantly higher sensitivity and responsiveness observed in the T47D line during preliminary 2D screenings, this cell line was exclusively selected for the development of the 3D spheroid model. Cells were treated with 17β-estradiol (E2), BPA, and Fulvestrant (FUL) to assess cell viability and luciferase activity. In 2D models, T47D ERE-LUC cells showed higher responsiveness than MCF7 ERE-LUC, which failed to show significant luciferase induction with E2. In the 3D T47D model, cells exhibited significant and robust changes in luciferase activity in response to E2 and BPA, highlighting the enhanced fidelity of 3D cultures in replicating tissue conditions compared to their 2D counterparts. The study highlights the effectiveness of 3D models over 2D in evaluating estrogenic activity. Specifically, the 3D T47D ERE-LUC system serves as a superior, sensitive, and reliable platform for screening EDCs, offering benefits in cost, data speed, and reduced in vivo reliance.

Humans

Plasma naltrexone kinetics after intravenous bolus administration in dogs and monkeys.

This investigation generated data characterize a specific electron-capture GLC assay reported previously for naltrexone and applied the method to a determination of naltrexone pharmacokinetics. Extraction efficiencies are reported for the assay, and mass spectral evidence indicates that naltrexone forms a triester when derivatized for electron-capture GLC with pentafluoropropionic anhydride and a base catalyst. Plasma level-time data for intravenous naltrexone at two dose levels in monkeys yielded no evidence of dose-dependent kinetics. A two-compartment open pharmacokinetic model was fitted to plasma level-time data for naltrexone in two dogs and yielded a total body clearance of 51-55 ml/min/kg. Urine collected for 0-24 hr contained 36% of the dose as naltrexone conjugates with less than 1% as unchanged naltrexone. Plasma level-time data for intravenous naltrexone in six monkeys yielded an average terminal half-life of 7.8 hr and a total body clearance of 64 ml/min/kg. The total body clearance for naltrexone was greater than the hepatic plasma or blood flow in both dogs and monkeys. This finding, together with the extremely low renal excretion of naltrexone, suggests the existence of elimination mechanisms besides liver metabolism and renal excretion.

Animals

Reporter Gene Assays to Measure FOXO-Specific Transcriptional Activity.

The forkhead box O (FOXO) family of transcription factors translates environmental cues into precise gene expression patterns maintaining cellular equilibrium while influencing critical determinations of cell destiny and differentiation. FOXO proteins exert their effects through specific consensus binding to promoter sites within target genes. Notably, among the array of techniques available for assessing the transcriptional activity of FOXO factors, the utilization of luciferase-based reporters emerges as particularly distinctive. Luciferase, an enzyme sourced from bioluminescent organisms, instigates the oxidation of luciferin, culminating in the generation of oxyluciferin accompanied by discernible luminescence, a quantifiable event readily gauged using a luminometer. The adoption of luciferase activity as a measure in transcriptional assays is widespread due to its numerous advantages including simplicity, remarkable reproducibility, and high sensitivity. Moreover, the continuous advancements witnessed in luciferase-based vectors and measurement reagents bestow notable flexibility upon this methodology. Luciferase-based reporters offer a powerful tool for uncovering constituents within the signaling pathways governing FOXO factor function. Furthermore, these assays are also suitable for evaluating the efficacy of FOXO-targeting agents, whether they be inhibitors or activators. Here, we present a comprehensive, step-by-step elucidation of a commonly employed assay, adeptly quantifying the potential of small molecular compounds to amplify FOXO-specific transcriptional activity in U2OS cells.

Genes, Reporter

IFNL1 gene promoter single nucleotide polymorphism rs7247086 enhances transcription through a STAT-binding site.

A single nucleotide polymorphism (SNP) within the human interferon lambda 1 (IFN-L1, IFN-λ1) gene promoter, rs7247086 (C/T) has been reported to be associated with severe dengue and possibly with psoriasis and COVID-19. However, its functional nature is unknown. The present study was undertaken to examine the effect of rs7247086 on transcription, by utilizing promoter and enhancer-reporter assays. We see that the T allele completes a consensus signal transducer and activator of transcription (STAT)-binding site. While we did not find strong evidence to show that the STAT-binding site drove transcription from the IFNL1 gene promoter, we saw that it acts like an enhancer in reporter assays. The T allele of rs7247086 within the STAT-binding site significantly increased transcription of the reporter gene compared to the C allele when incorporated into enhancer-reporter constructs in both HEK293 and A549 cell lines. Mechanistically, we obtained evidence from electrophoretic mobility shift assays to show that the T allele binds to STAT proteins more strongly than the C allele. In a cohort of healthy individuals, we saw that the T allele carriers, specifically males but not females, had significantly increased secretion of IFN-λ1 from their peripheral blood mononuclear cells after stimulation. Lastly, rs7247086 significantly associated with psoriasis, only in males but not in females.

Humans

Germline noncoding risk variants influence clonal hematopoiesis through altered hematopoietic enhancer activity.

Clonal hematopoiesis of indeterminate potential (CHIP) is a precursor condition characterized by the expansion of mutant hematopoietic stem and progenitor cell (HSPC) clones that increases the risk of hematologic malignancies. Although genome-wide association studies have identified multiple non-coding loci associated with CHIP susceptibility, their mechanisms remain unclear. We hypothesized that CHIP risk variants alter enhancer activity in HSPCs. To test this, we screened 1,374 non-coding variants from 51 CHIP-associated loci using a Massively Parallel Reporter Assay (MPRA) in the CD34+ fraction of MUTZ-3 cells. We identified 87 regulatory variants across 32 loci. Targeted genome editing in hematopoietic cells and complementary reporter assays in primary human HSPCs validated enhancer activity for variants regulating NKD2, FLT3, and MSI2. Functional studies demonstrated that increased MSI2 expression, modeling the effect of the CHIP risk allele, promotes clonal expansion of TET2-deficient HSPCs, providing a mechanistic link between inherited non-coding variation and CHIP clonal expansion.

Journal Article

ZNF695 Promotes Colorectal Cancer Progression Through Transcriptional Activation of CBX8 and Subsequent Wnt/β-Catenin Signaling Activation.

In this investigation, we examined the functional mechanism of the transcription factor zinc finger protein 695 (ZNF695) and its target gene chromobox protein homolog 8 (CBX8) in colorectal cancer (CRC) migration and invasion. HCT-116 and LOVO cell lines were used to establish cell models with knocked-down ZNF695 and knocked-down or over-expressed CBX8. To comprehensively evaluate the functional contributions of ZNF695 and CBX8 to cellular phenotypes, we employed CCK-8, wound-healing, and Transwell assays to evaluate cell proliferation, migration, and invasion, respectively. To assess the impact of ZNF695 on tumor progression, we generated a xenograft model utilizing nude mice. A FLAG-ZNF695 expression plasmid was constructed, and ChIP-seq experiments were performed. By integrating mRNA sequencing data following ZNF695 knockdown with highly expressed genes in CRC from the TCGA database, CBX8 was identified as a putative downstream target of ZNF695. We employed a dual-luciferase reporter assay to validate the specific binding affinity of ZNF695 toward the CBX8 promoter region. To elucidate the specific biological cascades modulated by ZNF695 and CBX8, we conducted a comprehensive pathway enrichment analysis. Rescue experiments were conducted to determine whether the ZNF695/CBX8 regulatory axis upregulates the expression of the Wnt signaling pathway downstream targets, AXIN2 and CCND1. Both in vitro assays and in vivo models confirmed that silencing ZNF695 dramatically suppresses CRC cell proliferation, migration, and invasion, while concurrently impeding tumor progression. ChIP-seq coupled with dual-luciferase reporter assays substantiated the direct binding of ZNF695 to the CBX8 promoter. Furthermore, CBX8 depletion significantly attenuated the migratory and invasive phenotypes of CRC cells. Restoring CBX8 expression effectively rescued the migratory and invasive deficits in CRC cells induced by ZNF695 silencing. Re-expression of CBX8 in ZNF695-silenced cells restored Wnt/β-catenin signaling activity, accompanied by increased expression of AXIN2 and CCND1. ZNF695 promotes CRC progression by transcriptionally activating CBX8 and subsequently enhancing Wnt/β-catenin signaling, thereby promoting tumor cell proliferation, migration, and invasion.

Humans

The toxin-antitoxin system SavRS contributes to vancomycin resistance in vancomycin-intermediate Staphylococcus aureus by mediating cell wall thickening.

BACKGROUND: The emergence of vancomycin-intermediate Staphylococcus aureus (VISA) has significantly challenged the treatment of S. aureus infection. Toxin-antitoxin (TA) systems have been reported to mediate bacterial stress adaptation and virulence, but their role in vancomycin resistance remains elusive. This study investigated the vancomycin resistance mechanism regulated by the TA system SavRS in VISA. METHODS: savRS mutants in Mu50 and XN108 were generated via homologous recombination. To investigate the regulatory mechanism of vancomycin resistance mediated by savRS in VISA, phenotypic analyses including MICs, growth kinetics and cell wall thickness measurements were performed. Expression of cell wall synthesis-related genes was analysed using quantitative RT-PCR (RT-qPCR) and promoter-lacZ reporter assay. Electrophoretic mobility shift assay (EMSA) was performed to assess the binding of SavRS to the promoters of the cell wall synthesis-related genes. Pull-down assay identified an upstream regulatory element of savRS associated with vancomycin resistance. Quantitative assessment of bacterial burden in murine organ systems following vancomycin administration revealed the critical regulatory role of savRS in mediating vancomycin resistance in vivo. RESULTS: Compared with the WT, the savRS mutant exhibited enhanced vancomycin sensitivity, accelerated growth and reduced cell wall thickness. Correspondingly, RT-qPCR revealed marked down-regulation of the cell wall synthesis-related genes (glyS, dltA, scdA, pbp2, ddl). EMSA and promoter-lacZ reporter assay confirmed direct binding of SavRS to a conserved promoter motif, MGHYYTCCTCA. Pull-down assay identified UspA as an upstream regulator of SavRS, demonstrating that UspA directly controls savRS transcription and modulates VISA resistance. Mouse infection experiments showed that savRS promotes VISA to vancomycin resistance in vivo. CONCLUSIONS: SavRS critically regulates vancomycin resistance in VISA.

Cell Wall

miR-6388 regulates granulosa cell function in sheep by targeting GDF9 and modulating the TGF-β signaling pathway.

Litter size is an economically important trait in sheep and is closely associated with ovarian follicular development and granulosa cell (GC) function. This study investigated the association between GDF9 polymorphisms and litter size, and examined the post-transcriptional regulation of GDF9 by miR-6388 in ovine GCs. Variants were initially identified by Sanger sequencing in 20 ewes, and subsequently genotyped in 377 three-year-old ewes, including 231 Sonid (SN) sheep and 146 Ujimqin (UM) sheep for association analysis. Candidate miRNAs targeting litter size-associated variants in the GDF9 3'UTR were predicted, and the miR-6388-GDF9 interaction was evaluated using dual-luciferase reporter assays. RT-qPCR, Western blotting, EdU incorporation, and flow cytometry were used to assess endogenous GDF9 expression and GC function. Twelve single-nucleotide polymorphisms were identified, including the putatively novel variant g.42114076C > G. The linkage disequilibrium block comprising g.42116936C > T, g.42113821T > A, and g.42113962G > A polymorphisms of GDF9 was significantly associated with litter size in both SN and UM sheep, whereas the c.477G > A was associated with litter size only in UM sheep. Reporter assays showed that the GDF9 3'UTR region carrying the G allele of g.42113962G > A was more responsive to miR-6388-mediated repression than the region carrying the A allele. miR-6388 overexpression reduced GDF9 mRNA and GDF9 protein levels, inhibited GC proliferation, altered cell-cycle distribution, and promoted apoptosis, whereas miR-6388 knockdown increased GDF9 expression and GC proliferation and reduced apoptosis. These cellular changes were accompanied by altered expression of cell-cycle and apoptosis-related genes and TGF-β signaling-related components.

Animals

LncRNA DNAJC3-AS1 promotes gastric cancer malignancy through miR-576-5p-mediated upregulation of LYPLA1.

Long non-coding RNAs (lncRNAs) are involved in tumor progression, but the role of lnc-DNAJC3-AS1 in gastric cancer (GC) remains unclear. This study aimed to investigate the biological function and regulatory mechanism of lnc-DNAJC3-AS1 in GC. Reverse transcription quantitative PCR (RT-qPCR) was used to detect the expression levels of lnc-DNAJC3-AS1, miR-576-5p, and LYPLA1, and Western blot was used to analyze protein expression. The Cancer Genome Atlas (TCGA) database and clinical samples were used to evaluate their clinical relevance. Cell viability, cell cycle distribution, apoptosis, migration, and invasion were assessed using Cell Counting Kit-8 (CCK-8), flow cytometry, wound-healing, Transwell, and immunofluorescence assays. Dual-luciferase reporter assay, RNA immunoprecipitation (RIP), fluorescence in situ hybridization (FISH), and rescue assays were performed to explore the potential regulatory relationship among lnc-DNAJC3-AS1, miR-576-5p, and LYPLA1. A xenograft tumor model was also established to evaluate the role of lnc-DNAJC3-AS1 in vivo. The results showed that lnc-DNAJC3-AS1 and LYPLA1 were upregulated, whereas miR-576-5p was downregulated in GC tissues and cells. Knockdown of lnc-DNAJC3-AS1 inhibited GC cell viability, migration, and invasion, induced G0/G1 phase arrest and apoptosis, and suppressed tumor growth in vivo. Mechanistically, lnc-DNAJC3-AS1 was mainly localized in the cytoplasm and was associated with miR-576-5p-related RNA-induced silencing complex (RISC) complexes. MiR-576-5p targeted LYPLA1, and restoration of miR-576-5p or knockdown of LYPLA1 partially attenuated the effects of lnc-DNAJC3-AS1 overexpression on GC cell phenotypes and LYPLA1 enzymatic activity. These findings suggest that lnc-DNAJC3-AS1 promotes GC progression, at least in part, through the miR-576-5p/LYPLA1 pathway, providing a potential target for GC treatment.

Gastric cancer

A general framework to over-express tRNA-derived fragments from their parental tRNAs in mammalian cells.

tRNA-derived fragments (tRFs), generated from the cleavage of mature or precursor tRNAs are a category of regulatory noncoding RNAs with diverse functions in physiological or pathophysiological conditions. Here we describe a framework for the over-expression of tRFs from their parental tRNAs in mammalian cells. The process involves bioinformatics analysis to identify specific tRNAs that produce the tRF, PCR amplification of corresponding tRNA genes, and insertion into expression vectors. Transfection is carried out in HEK293T cells and detection of tRFs is achieved through northern blotting and dual luciferase reporter assays. In the latter, a complementary sequence to the tRF of interest is inserted into the luciferase reporter. By observing the reduction in luciferase activity, we can validate the expression of tRFs. This method enables precise study of tRF functions and their roles in cellular processes.

Humans

A systematic strategy for identifying causal single nucleotide polymorphisms and their target genes on Juvenile arthritis risk haplotypes.

BACKGROUND: Although genome-wide association studies (GWAS) have identified multiple regions conferring genetic risk for juvenile idiopathic arthritis (JIA), we are still faced with the task of identifying the single nucleotide polymorphisms (SNPs) on the disease haplotypes that exert the biological effects that confer risk. Until we identify the risk-driving variants, identifying the genes influenced by these variants, and therefore translating genetic information to improved clinical care, will remain an insurmountable task. We used a function-based approach for identifying causal variant candidates and the target genes on JIA risk haplotypes. METHODS: We used a massively parallel reporter assay (MPRA) in myeloid K562 cells to query the effects of 5,226 SNPs in non-coding regions on JIA risk haplotypes for their ability to alter gene expression when compared to the common allele. The assay relies on 180 bp oligonucleotide reporters ("oligos") in which the allele of interest is flanked by its cognate genomic sequence. Barcodes were added randomly by PCR to each oligo to achieve > 20 barcodes per oligo to provide a quantitative read-out of gene expression for each allele. Assays were performed in both unstimulated K562 cells and cells stimulated overnight with interferon gamma (IFNg). As proof of concept, we then used CRISPRi to demonstrate the feasibility of identifying the genes regulated by enhancers harboring expression-altering SNPs. RESULTS: We identified 553 expression-altering SNPs in unstimulated K562 cells and an additional 490 in cells stimulated with IFNg. We further filtered the SNPs to identify those plausibly situated within functional chromatin, using open chromatin and H3K27ac ChIPseq peaks in unstimulated cells and open chromatin plus H3K4me1 in stimulated cells. These procedures yielded 42 unique SNPs (total = 84) for each set. Using CRISPRi, we demonstrated that enhancers harboring MPRA-screened variants in the TRAF1 and LNPEP/ERAP2 loci regulated multiple genes, suggesting complex influences of disease-driving variants. CONCLUSION: Using MPRA and CRISPRi, JIA risk haplotypes can be queried to identify plausible candidates for disease-driving variants. Once these candidate variants are identified, target genes can be identified using CRISPRi informed by the 3D chromatin structures that encompass the risk haplotypes.

Humans