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Analysis of different expression RNA binding protein genes in mouse microglia cell from the brains of mice 72 h after subarachnoid hemorrhage or sham operation.

BACKGROUND: The prognosis of brain injury caused by subarachnoid hemorrhage (SAH) is poor. Previous studies showed that abnormal function of RBPs might be involved in brain injury, neuroinflammation and further affect microglia homeostasis. However, no studies have systematically analyzed the genome-wide abnormal expression of RBPs genes in microglia during SAH. METHODS: RNA-seq data of microglia from the SAH mouse group (SAH) and control sham-operated mouse group (sham) were downloaded from the GEO database in GSE167957, including four samples from the sham group and four samples from the SAH group for subsequent analysis.Utilizing GO and KEGG functional enrichment analyses, we conducted a comprehensive study of differentially expressed genes (DEGs), alternative splicing patterns, and co-expression networks to gain deeper insights into the differential expression of RNA-binding proteins (RBPs) and differential alternative splicing events (ASEs) between the SAH (subarachnoid hemorrhage) and sham groups. This analysis aimed to elucidate the potential mechanisms underlying the aberrant expression of RBPs in microglia during brain injury caused by SAH. RESULTS: ASEs and co-expression analyses of differentially expressed RBPs and differential ASEs were carried out in microglia in terms of gene expression. GO and KEGG functional enrichment analysis showed that aberrantly expressed RBPs such as Mcm7, Mtdh, SRSF3, and Hnrnpa2b1 may affect and regulate downstream Csnk1d, Uckl1 and other protein phosphorylation-related genes by alterative splicing. CONCLUSION: RBPs were aberrantly expressed in microglia during the development of brain injury secondary to SAH, regulating alterative splicing of downstream genes and influencing the progression of SAH brain injury in this study. This implies that RBPs are important for the identification of new therapeutic targets for brain injury after SAH.

Animals

The structured mRNA element 45ABC mediates auto- and cross-regulation of RBP45 genes via alternative splicing.

Alternative splicing (AS) is a common gene regulatory mechanism involving distinct interactions between trans-acting factors and cis-regulatory elements on the precursor messenger RNA (pre-mRNA). In this study, we have functionally characterized the structured motif 45ABC, which is located in the pre-mRNAs of RNA-binding protein (RBP) 45 genes in many plant species. Our data revealed that this element mediates a negative auto- and cross-regulatory feedback loop via AS of the three 45ABC-containing RBP45 genes in Arabidopsis thaliana. We identified a G-rich stretch within the first stem as a potential RBP45 binding site and observed increased RBP45-dependent AS upon structural weakening of this pairing element. The second stem includes the alternative 5' splice site being activated in the presence of RBP45. Based on the known interaction between RBP45 homologs and U1 snRNP components required for 5' splice site recognition, we propose that RBP45 recruitment to stem I of 45ABC may induce usage of the alternative 5' splice site in stem II. The resulting splicing variant is unproductive, thereby diminishing RBP45 expression. Analysing the splicing-regulatory impact of the three At-RBP45 genes in auto- and cross-regulation and a transcriptome-wide manner revealed unequal genetic redundancy with a major role of RBP45B. Furthermore, phenotypical analysis of single- and higher-order rbp45 mutants pointed at these genes' functions in controlling primary root growth and flowering time. Taken together, we demonstrated that both sequence and structural features of 45ABC are critical for proper splicing control, balancing RBP45 expression and functions in plants via a conserved mRNA motif.

Alternative Splicing

Musashi1 Contribution to Glioblastoma Development via Regulation of a Network of DNA Replication, Cell Cycle and Division Genes.

RNA-binding proteins (RBPs) function as master regulators of gene expression. Alterations in their levels are often observed in tumors with numerous oncogenic RBPs identified in recent years. Musashi1 (Msi1) is an RBP and stem cell gene that controls the balance between self-renewal and differentiation. High Msi1 levels have been observed in multiple tumors including glioblastoma and are often associated with poor patient outcomes and tumor growth. A comprehensive genomic analysis identified a network of cell cycle/division and DNA replication genes and established these processes as Msi1's core regulatory functions in glioblastoma. Msi1 controls this gene network via two mechanisms: direct interaction and indirect regulation mediated by the transcription factors E2F2 and E2F8. Moreover, glioblastoma lines with Msi1 knockout (KO) displayed increased sensitivity to cell cycle and DNA replication inhibitors. Our results suggest that a drug combination strategy (Msi1 + cell cycle/DNA replication inhibitors) could be a viable route to treat glioblastoma.

DNA replication

Rbp-Jκ controls NK cell late maturation and migration via chromatin landscape remodeling.

The transcriptional regulator Rbp-Jκ is a pivotal molecular switch in Notch signaling; however, its cell-intrinsic role in natural killer (NK) cell maturation and migration remains incompletely understood. Here, we demonstrate that NK cell-specific deletion of Rbp-Jκ (Ncr1iCre × Rbp-Jκfl/fl, Rbp-JκΔNK) impairs NK cell terminal maturation and migration, as evidenced by increased retention of NK cells in bone marrow, a reduced number of circulating NK cells and decreased expression of migration mediators (CD62L, S1pr5, and Cx3cr1). Despite exhibiting an activated phenotype, Rbp-Jκ-deficient NK cells fail to control B16F10 lung metastases in vivo because of impaired tissue mobilization. Multiomics (scRNA-seq/scATAC-seq, bulk ATAC-seq, and CUT&Tag) reveal that Rbp-Jκ orchestrates chromatin remodeling in NK cells, suppressing the expression of genes related to NK cell activation and cytotoxicity while promoting the expression of genes involved in ribosome and oxidative phosphorylation. Notably, Rbp-Jκ directly binds to the Kruppel-like factor 2 (Klf2) promoter, and loss of Rbp-Jκ reduces both the mRNA and protein levels of Klf2. Klf2 overexpression rescues the decreased expression of CD62L and CX3CR1 in Rbp-Jκ-deficient NK cells. The cooccupancy of Rbp-Jκ and Klf2 at shared genomic loci is confirmed by ChIP-qPCR. In summary, our study reveals that Rbp-Jκ acts as a master regulator of NK cell terminal maturation and tissue homing via chromatin reprogramming, with Klf2 acting as its critical downstream transcription factor.

Animals

Identification of RBP binding sites using RNA deaminases.

RNA-binding proteins (RBPs) are critical regulators of gene expression and RNA processing. Identification of their binding sites has important implications for their physiological and disease-related functions. Crosslinking and immunoprecipitation, followed by sequencing (CLIP-seq) and its derivatives, are the most commonly used methods to identify RBP binding sites, but are laborious and require a large amount of starting material. Recent advancements harnessing RNA deaminases in fusion to any RBP of interest, allow for the profiling of RBP binding sites from low-input samples in simpler procedures. Among these efforts, we developed STAMP (Surveying Targets by APOBEC-Mediated Profiling), which efficiently detects RBP-RNA interactions. This chapter describes the detailed protocol for the STAMP method, including plasmid construction, delivery and sorting, library preparation and bioinformatic data analysis.

RNA-Binding Proteins

Integrated multi-omics identification of m6A-SNP-related diagnostic biomarkers in amyotrophic lateral sclerosis.

BACKGROUND: Amyotrophic lateral sclerosis (ALS) lacks reliable and minimally invasive biomarkers for early diagnosis. m6A-associated single-nucleotide polymorphisms (m6A-SNPs) may influence RNA methylation and gene expression, offering opportunities to identify clinically relevant diagnostic markers. METHODS: We integrated eQTLGen cis-eQTL data, RMVar m6A-SNP annotations, and ALS transcriptomic datasets to identify m6A-SNP-related genes. Random Forest and LASSO regression were combined to screen robust diagnostic markers. A nomogram was constructed and validated using independent cohorts. Immune infiltration, predicted m6A modification sites, and potential RBP-SNP interactions were assessed. Peripheral blood samples from ALS patients were used for exploratory validation of gene expression and global m6A levels. RESULTS: We identified 109 ALS-associated m6A-SNP-related genes with cis-eQTL signals and narrowed these to seven candidate diagnostic markers (TMED5, OXR1, BRI3, FEM1C, SUZ12, EIF2AK4, and TJAP1). The seven-gene model outperformed the individual markers in the training cohort and retained moderate discrimination in the independent validation cohort. ALS samples showed differences in inferred immune-cell composition, including monocytes, neutrophils, and T-cell subsets. The selected SNP loci were located near predicted m6A sites and annotated RBP-binding regions. Exploratory clinical validation showed significant upregulation of FEM1C and SUZ12 at both mRNA and protein levels, accompanied by reduced global m6A modification. CONCLUSIONS: Through multi-omics integration and exploratory clinical validation, this study identifies m6A-SNP-related candidate markers associated with ALS. The findings support further evaluation of m6A-related signatures for ALS discrimination and molecular characterization, while larger independent cohorts and additional calibration are required before clinical application.

Humans

Avian riboflavinuria IX. Qualitative action of a mutant gene in chicken on riboflavin-binding protein synthesis.

Laying chickens normally produce a riboflavin-binding protein (RBP) essential for the transfer of vitamin B2 to the egg. A mutant line of chickens (rdrd) is incapable of synthesizing functional RBP. The rdrd laying hens contain a component in the liver and the magnum of the oviduct which cross-reacts with rabbit antiserum specific for RBP. No crossreacting material (CRM) was observed in eggs or blood of rdrd hens. CRM is absent in extracts of livers of rdrd males, but it can be induced in roosters of this genotype by estradiol. CRM appears to be less immunogenic on a weight basis than RBP, and it carries less net negative charge. No measurable riboflavin-binding capacity was found for newly isolated or degraded CRM.

Animals

Identification of a necroptosis-related lncRNA prognostic signature and the hub RBP HNRNPK in esophageal squamous cell carcinoma.

ObjectiveEsophageal squamous cell carcinoma (ESCC) is a malignant tumor with poor prognosis. Necroptosis is important for tumor immunity, but its role in ESCC remains unclear. This retrospective bioinformatics study aimed to investigate the prognostic value of necroptosis-related long non-coding RNAs (lncRNAs) and to identify key lncRNA-binding proteins (RBPs) in ESCC patients.MethodsRNA transcriptome and clinical data of ESCC patients were obtained from The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) databases. Necroptosis-related lncRNAs were identified through correlation analysis with necroptosis-related genes, subjected to consensus cluster analysis, and used to construct a prognostic risk model via least absolute shrinkage and selection operator (LASSO) regression. The hub RBP was experimentally validated by quantitative polymerase chain reaction (qPCR) using 30 pairs of ESCC and adjacent normal tissues from patients who underwent surgical resection.ResultsA total of 30 necroptosis-related lncRNAs were significantly correlated with overall survival (OS). The upregulated lncRNAs in the risk model were associated with high immune scores, innate immune cell infiltration, cluster 2 classification, and advanced T-stage disease (p&#x2009;<&#x2009;0.05). Three hub RBPs (HNRNPA1, HNRNPC, and HNRNPK) were identified through protein-protein interaction network analysis. qPCR confirmed that HNRNPK was significantly overexpressed in ESCC tissues compared to adjacent normal tissues (p&#x2009;<&#x2009;0.05).ConclusionsThe necroptosis-related lncRNA risk model is an independent prognostic factor for ESCC patients. HNRNPK was identified as a hub RBP significantly overexpressed in ESCC tissues. We hypothesize that HNRNPK may promote tumor progression through regulating proto-oncogene expression or modulating the immune microenvironment, though this requires further mechanistic validation.

Humans

Effect of TGF beta on liver genes expression. Antagonistic effect of TGF beta on IL-6-stimulated genes in Hep 3B cells.

The effect of transforming growth factor beta (TGF beta) on the expression of a group of liver genes has been investigated in the hepatoma cell line Hep 3B. TGF beta induces a decrease of the basal level of apolipoprotein A-II (ApoA-II), retinol binding protein (RBP) and alpha-fetoprotein (alpha Fp). Furthermore, TGF beta efficiently antagonizes the IL-6-induction of hemopexin (Hpx) and haptoglobin (Hp) and alpha 1-acid glycoprotein (AGP). These effects of TGF beta are apparently mediated by post-transcriptional mechanism(s). These findings, together with previously reported data on the inhibitory effect of TGF beta on acute phase genes (e.g. ApoA-I and albumin), suggest a role for TGF beta in the regulation of expression of liver genes.

Apolipoprotein A-II

Proposed interaction between insulin and retinoblastoma protein.

Retinoblastoma protein (RB) is a tumor suppressor gene product involved in embryogenesis and cell cycle progression. One of the major mechanisms leading to RB dysfunction is complex formation with viral oncoproteins using the common RB binding motif Leu X Cys X Glu (LXCXE) which has also been identified in cellular ligands, e.g., RBP-1 and RBP-2. p107, a cellular protein with RB sequence homology, has been shown to bind to the same viral oncoproteins associating with RB and is therefore thought to contribute to cell cycle regulation. It has recently been suggested that insulin stimulates gene transcription through direct association with an, as yet, unidentified intracellular transcription factor. Due to the central roles of RB and p107 in coupling external growth signals with the progression of the cell cycle clock, we have hypothesized that these two proteins might be candidates for mediating the effects of insulin on DNA. We report here the identification of a region in the B-chain of human insulin that has the sequence LXCXE. Based on this finding we predict that the insulin B-chain may interact with RB and/or p107. Since we have also identified sequences hydropathically related to LXCXE in insulin-like growth factor I (IGF-I) and II (IGF-II), but not in relaxin, nerve growth factor, epidermal growth factor, glucagon or beta-endorphin, we further propose that both IGF-I and -II may assemble with RB and/or p107, too. Moreover, binding sites on RB and p107 identical with those suggested for viral oncoproteins and cellular ligands are predicted for insulin/IGF-I/IGF-II by using the hydropathic complementarity approach.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence

ARID5A RNA-binding coordinates microglial defense and ferroptosis in iPSC-derived models.

RNA-binding proteins (RBPs) are key regulators of gene expression that shape cellular function in health and disease. However, the roles of RBPs in immune cells within the central nervous system (CNS) remain poorly understood. Here, we identify ARID5A as an RBP highly expressed in microglia and uncover its RNA-mediated regulatory functions using integrated multi-omics analyses of its RNA, DNA, and protein interactions. ARID5A regulates the splicing and translation of its RNA targets, many of which are integral to lysosomal, immune, and iron metabolism pathways. We confirm the functional relevance of this ARID5A-dependent RNA regulatory network by demonstrating that ARID5A modulates lysosomal activity, cytokine secretion, iron accumulation, and ferroptosis in iPSC-derived microglia. We further demonstrate that knockdown of microglial ARID5A reduces neuronal ferroptosis in co-cultures, underscoring the interconnected nature of these pathways. Moreover, in microglia harboring the TREM2-T66M mutation, ARID5A depletion restores dysregulated lysosomal and metabolic functions. Our results highlight the importance of protein-RNA interactions in regulating microglial cell biology.

Microglia

Hexokinase 2 is an RNA-binding protein that regulates mRNA translation independently of glycolysis and induces melanoma cell proliferation.

Although metabolic benefits of glycolysis have been extensively described in tumor cells, the extra-metabolic functions linked to this energetic pathway in tumor growth and cell proliferation have not been clearly established yet. Recently, some key glycolytic enzymes, such as glyceraldehyde-3-phosphate dehydrogenase and pyruvate kinase 2, were reported to regulate mRNA translation. Translational control of gene expression is considered as a critical effector in cancer biology, representing a highly promising area of research. Here, we report that Hexokinase 2 (HK2), a glucose kinase that catalyzes the first step of glycolysis at the outer mitochondrial membrane (OMM), is an RNA-binding protein (RBP) that regulates mRNA translation in melanoma cell lines. Polysome profiling experiments followed by RNA sequencing indicate that the translational regulation exerted by HK2 is partly independent of the metabolic status or the glycolytic pathway. We found that HK2 specifically regulates translation of the mRNA encoding SOX10, a transcription factor implicated in the regulation of tumor initiation, maintenance, and progression in melanoma. RNA-protein interaction assays, including CrossLinking ImmunoPrecipitation (CLIP), indicate that HK2 is an RBP whose interaction with RNA is independent of its enzymatic activity, its ability to bind glucose or its association with the OMM. HK2 directly interacts with the 5' untranslated region (5'UTR) of the SOX10 mRNA through a stem-loop RNA secondary structure. Using RNA-protein proximity ligation assays and a fluorescence-based ribosome-bound mRNA mapping method, we found that high glucose conditions, which promote the release of HK2 from the OMM, induce an increase in HK2-SOX10 mRNA interaction and SOX10 mRNA translation in the cytoplasm. We further showed that HK2-dependent SOX10 mRNA translation is involved in melanoma cell proliferation and colony formation. Collectively, our data highlight a nonmetabolic function of HK2 acting as an RBP and translation regulator.

Hexokinase

Variants leading to ELAVL2 haploinsufficiency cause a neurodevelopmental disorder with prominent cognitive, behavioral, and neurological features.

RNA-binding proteins (RBPs) regulate gene expression, and a number of RBPs have been implicated in brain function and behavior. Here, we report 16 individuals with a neurodevelopmental disorder and de novo heterozygous variants in ELAVL2, encoding an RBP not previously linked to Mendelian disease. Thirteen individuals were identified through GeneMatcher. Their ELAVL2 variants include two structural, five nonsense, and six missense variants, supporting haploinsufficiency as the primary disease mechanism. The cohort presented with developmental delay, intellectual disability, autism spectrum disorder, seizures, sleep problems, sensory processing issues, emotional instability, and difficulty with socialization. Three additional variants (two missense and one terminal exon truncation), each previously reported in a different large cohort study, were also included for follow-up investigations. We provide multiple lines of evidence linking variants in ELAVL2 to the observed neurodevelopmental and behavioral phenotypes. First, we show that common genetic variants in ELAVL2 are significantly associated with intelligence, motor development, sleep-related traits, and sociability in the general population. Drosophila loss-of-function models provide further independent evidence for a conserved role in the regulation of seizure-like behavior, sensory processing, and sleep. Molecular studies confirm that some of the missense variants are deleterious, leading to decreased protein levels. Together, our integrative study combining Mendelian genetics, clinical and association studies, and animal and molecular modeling supports variants in ELAVL2 as a cause of a neurodevelopmental disorder, with haploinsufficiency as the disease mechanism, and identifies crucial roles of ELAVL2 in neuronal function, cognition, and behavior.

Humans

Prenatal BPA exposure perturbs RNA-binding protein-mediated splicing regulation and synaptogenesis in the developing cerebellum in a sex-dependent manner.

BACKGROUND: Autism spectrum disorder (ASD) is a pervasive neurodevelopmental condition characterized by social communication deficits, exhibiting a male bias in prevalence. Emerging evidence suggests that prenatal exposure to bisphenol A (BPA) may perturb neurodevelopmental trajectories relevant to ASD. While the cerebellum is increasingly recognized as a brain region implicated in ASD pathophysiology, the impact of gestational BPA exposure on its post-transcriptional alternative splicing machinery remains fundamentally undefined. METHODS: Here, we investigated sex-dependent effects of prenatal BPA exposure on the alternative splicing landscape of the neonatal rat cerebellum. We utilized RNA-seq to profile differential alternative splicing (DAS) events. Ingenuity Pathway Analysis (IPA) was used to predict biological functions and canonical pathways, and to construct the interactome network of DAS genes. To explore candidate upstream regulatory mechanisms, we performed in silico molecular docking and used high-resolution melting (HRM) qRT-PCR to validate selected splicing events. Furthermore, we assessed in vitro cellular phenotypes in primary cerebellar neurons by measuring MTS-based viability and Syn1/Psd95 puncta colocalization. RESULTS: Prenatal BPA exposure was associated with widespread DAS in genes enriched for ASD-relevant pathways in the neonatal rat cerebellum. To our knowledge, this study is the first to report molecular docking analyses predicting favorable interactions between BPA and several candidate RNA-binding proteins (RBPs), including CPEB1, RALYL, HNRNPDL, and ACO1. Our findings support a model in which BPA may perturb RBP-associated splicing regulation, including altered splicing of chromatin regulators such as Ccar1 in males. These molecular and cellular findings were accompanied by sex-stratified differences in neuronal viability and synaptic puncta measurements. BPA exposure was associated with an increased MTS viability signal in male primary cerebellar neurons, together with significant reductions in Psd95 and Syn1 puncta density, whereas female neurons showed significantly increased synaptic puncta colocalization together with reduced viability. CONCLUSIONS: In this study, we propose that prenatal BPA may be relevant to ASD-related neurodevelopmental pathways through sex-dependent changes in RBP-associated alternative splicing, including altered splicing of Ccar1 in males, together with distinct cellular outcomes. Together, these findings identify the developing cerebellum as a sensitive target of prenatal BPA exposure and highlight alternative splicing as a candidate pathway relevant to ASD biology.

Animals

Genetic regulation of CPEB3-mediated alternative polyadenylation associated with survival of patients with hepatocellular carcinoma.

BACKGROUND: Alternative polyadenylation (APA) is a key post-transcriptional mechanism that regulates gene expression by modulating 3'UTR length, its dysregulation has been implicated in carcinogenesis. How genetic variants influence APA to affect hepatocellular carcinoma (HCC) prognosis remains unclear. METHODS: Prognosis-APA quantitative trait loci (apaQTL) were performed using genotype and APA profiling from TCGA data. A two-stage survival analysis in 848 Chinese and 369 TCGA LIHC patients and functional validation were used to identify prognostic apaQTL in HCC progression. RESULTS: A total of 2,025 and 817 significant APA events were identified in Chinese and TCGA cohort, respectively. Besides, 859 events were associated with poor prognosis in HCC and enriched in RNA splicing / metabolism pathways. We detected 32,034 significant apaQTLs, predominantly enriched in 3'UTRs and RBP-binding regions. CPEB3 was prioritized as a key APA regulator RBP; its low expression correlated with poor patient survival and promoted proliferation, migration, and invasion in HCC cells. Notably, a functional apaQTL variant rs2037547, located in GSK3B and mediated by CPEB3, demonstrated a poor survival of HCC patients in both cohort (pooled HR=1.29, p=0.016). Mechanistically, rs2037547 promoted aberrant APA at proximal poly(A) sites of GSK3B through CPEB3, leading to increased expression of short 3'UTR isoform. This regulatory alteration enhanced HCC cell proliferation, invasion, and migration, and contributed to HCC progression. CONCLUSION: These findings elucidated the distinct role of apaQTL-mediated APA dysregulation in HCC prognosis, providing insights for prognostic stratification and potential targets for personalized therapy in HCC.

RNA-binding proteins

[Mechanism of action of retinoids in a new therapeutic approach to acute promyelocytic leukemia].

Vitamin A (retinol) and retinoic acid, its natural derivative, play an important role in the growth, differentiation and development of known normal tissues. Retinoids have recently become of interest to research in areas as diverse as dermatology, embryonal development and cancer research. Retinol is the major retinoid transported in the blood and tissues by its specific carrier retinol binding protein (RBP). The normal level of retinol in plasma is regulated very precisely by retinol homeostasis. RBP-retinol circulation supplies target cells, which then activate retinol into retinoic acid (RA) if they possess the NAD-dependent enzymatic oxidation system. RA, which is one of the most active metabolites of retinol, is also present in low concentration in the blood and the RA rate formation varies from tissues depending on specific need of the cell. The cellular transport and biological activity of retinoids may be mediated by their specific cytoplasmic binding proteins cellular retinol binding protein (CRBP) and the cellular retinoic acid binding protein (CRABP) which may function as shuttles targetting RA to nucleosol fraction and/or as regulator of cellular concentration of RA. The nuclear proteins RARs (retinoic acid receptors), which are members of the nuclear receptor superfamily are likely to be the final transducers of the RA signal at the gene expression. All-trans retinoic acid (ATRA) is able to specifically differentiate the malignant cells from leukemic patients with APL in short-term culture. For this reason, APL patients were successfully treated with ATRA (Chinese and French results). Acute promyelocytic leukemia M3 (French-American-British FAB classification) is a rare disease (10% of AML), characterized by a reciprocal chromosome 15-17 translocation. It has been shown that the chromosome 17 breakpoint of the translocation is localized within the RAR alpha gene. Due to the t(15;17) RAR alpha gene translocated to a gene PML on chromosome 15 resulting in synthesis of PML/RAR alpha fusion messenger RNA. Detection of PML/RAR alpha transcript is now a molecular marker of the disease. The abnormal PML/RAR alpha protein exhibits altered transcription activation properties when compared with RAR alpha. Clinical trials have demonstrated that ATRA is extremely efficient in inducing complete remission in APL patients. The morphologic finding of maturing elements in the bone marrow and peripheral blood during retinoic acid treatment indicates that the remission is obtained without hypoplasia and suggests that a differentiating mechanism is involved.(ABSTRACT TRUNCATED AT 400 WORDS)

Carrier Proteins

Mudskipper detects combinatorial RNA binding protein interactions in multiplexed CLIP data.

The uncovering of protein-RNA interactions enables a deeper understanding of RNA processing. Recent multiplexed crosslinking and immunoprecipitation (CLIP) technologies such as antibody-barcoded eCLIP (ABC) dramatically increase the throughput of mapping RNA binding protein (RBP) binding sites. However, multiplex CLIP datasets are multivariate, and each RBP suffers non-uniform signal-to-noise ratio. To address this, we developed Mudskipper, a versatile computational suite comprising two components: a Dirichlet multinomial mixture model to account for the multivariate nature of ABC datasets and a softmasking approach that identifies and removes non-specific protein-RNA interactions in RBPs with low signal-to-noise ratio. Mudskipper demonstrates superior precision and recall over existing tools on multiplex datasets and supports analysis of repetitive elements and small non-coding RNAs. Our findings unravel splicing outcomes and variant-associated disruptions, enabling higher-throughput investigations into diseases and regulation mediated by RBPs.

RNA-Binding Proteins

Genome-scale CRISPR screening uncovers SRSF6 as a target to sensitize hepatocellular carcinoma to radiotherapy.

BACKGROUND & AIMS: Radiotherapy confers clinical benefits to patients with hepatocellular carcinoma (HCC) across all stages, yet its clinical efficacy is limited by radioresistance. This study aimed to identify key regulators of HCC radiosensitivity through genome-wide functional screening. METHODS: A genome-wide CRISPR-Cas9 screen in Huh7 cells identified radiosensitivity regulators, with SRSF6 validated by siRNA knockdown and &#x3b3;-H2AX assessment. Stable shRNA-mediated SRSF6 knockdown was established in Huh7 and HepG2 cells, followed by clonogenic, EdU incorporation, apoptosis, micronucleus, and comet assays. Mechanistically, RNA-seq, Western blotting, mRNA stability assays, RIP-qPCR, and RAD51 overexpression rescue assays were performed. The therapeutic potential of the SRSF6 inhibitor indacaterol was evaluated using MTS assays, HCC xenograft mouse models (BALB/c-nu/nu, n = 28), and HCC patient-derived organoids (PDOs) (n = 3). In addition, SRSF6 expression and its correlation with patient survival were analyzed using data from The Cancer Genome Atlas and a tissue microarray (n = 14 HCC and 14 paired adjacent non-tumorous liver samples). RESULTS: We identified the RNA-binding protein SRSF6 as a driver of HCC radioresistance. SRSF6 depletion enhanced the radiosensitivity of HCC cells (p <0.05-0.0001) by post-transcriptionally destabilizing the mRNAs of critical DNA repair genes (p <0.05-0.0001), thereby impairing radiation-induced DNA damage repair. The radiosensitizing effect of SRSF6 depletion was partially abrogated by ectopic overexpression of the core DNA repair protein RAD51 (p <0.05-0.001). Indacaterol exhibited cytotoxic effects on HCC cells (p <0.05-0.0001) and enhanced the antitumor efficacy of radiation in vivo (p <0.05-0.0001), as further validated across multiple HCC patient-derived organoids (p <0.05-0.0001). CONCLUSIONS: SRSF6 is a key regulator of HCC radioresistance through its post-transcriptional control of DNA repair capacity, and represents a novel therapeutic target to sensitize HCC to radiotherapy. IMPACT AND IMPLICATIONS: In this study, we performed a genome-wide CRISPR-Cas9 knockout library screen to dissect the molecular determinants governing HCC radiosensitivity, and identified RNA-binding protein SRSF6 as a driver of HCC radioresistance. We demonstrate that SRSF6 depletion disrupts the post-transcriptional stability of key DNA repair gene mRNAs and enhances HCC radiosensitivity. These findings are important for radiation oncologists and translational researchers, as they identify SRSF6-dependent RNA regulation as a critical determinant of radiotherapy response in HCC. Practically, we show that the clinically approved bronchodilator indacaterol suppresses SRSF6 function and enhances the antitumor efficacy of radiotherapy, offering a readily repurposable pharmacological strategy to overcome radioresistance. These implications are based on preclinical evidence across multiple models; however, future clinical trials are needed to validate the safety and efficacy of indacaterol-based radiosensitization in patients with HCC.

DNA repair