Ribonucleoprotein Biogenesis Research Articles

Endogenous adenine mediates kidney injury in diabetic models and predicts diabetic kidney disease in patients.

Diabetic kidney disease (DKD) can lead to end-stage kidney disease (ESKD) and mortality; however, few mechanistic biomarkers are available for high-risk patients, especially those without macroalbuminuria. Urine from participants with diabetes from the Chronic Renal Insufficiency Cohort (CRIC) study, the Singapore Study of Macro-angiopathy and Micro-vascular Reactivity in Type 2 Diabetes (SMART2D), and the American Indian Study determined whether urine adenine/creatinine ratio (UAdCR) could be a mechanistic biomarker for ESKD. ESKD and mortality were associated with the highest UAdCR tertile in the CRIC study and SMART2D. ESKD was associated with the highest UAdCR tertile in patients without macroalbuminuria in the CRIC study, SMART2D, and the American Indian study. Empagliflozin lowered UAdCR in nonmacroalbuminuric participants. Spatial metabolomics localized adenine to kidney pathology, and single-cell transcriptomics identified ribonucleoprotein biogenesis as a top pathway in proximal tubules of patients without macroalbuminuria, implicating mTOR. Adenine stimulated matrix in tubular cells via mTOR and stimulated mTOR in mouse kidneys. A specific inhibitor of adenine production was found to reduce kidney hypertrophy and kidney injury in diabetic mice. We propose that endogenous adenine may be a causative factor in DKD.

The cancer testis antigen TDRD1 regulates prostate cancer proliferation by associating with the snRNP biogenesis machinery.

Prostate cancer is the most commonly diagnosed noncutaneous cancer in American men. TDRD1, a germ cell-specific gene, is erroneously expressed in more than half of prostate tumors, but its role in prostate cancer development remains elusive. In this study, we identified a PRMT5-TDRD1 signaling axis that regulates the proliferation of prostate cancer cells. PRMT5 is a protein arginine methyltransferase essential for small nuclear ribonucleoprotein (snRNP) biogenesis. Methylation of Sm proteins by PRMT5 is a critical initiation step for assembling snRNPs in the cytoplasm, and the final snRNP assembly takes place in Cajal bodies in the nucleus. By mass spectrum analysis, we found that TDRD1 interacts with multiple subunits of the snRNP biogenesis machinery. In the cytoplasm, TDRD1 interacts with methylated Sm proteins in a PRMT5-dependent manner. In the nucleus, TDRD1 interacts with Coilin, the scaffold protein of Cajal bodies. Ablation of TDRD1 in prostate cancer cells disrupted the integrity of Cajal bodies, affected the snRNP biogenesis, and reduced cell proliferation. Taken together, this study represents the first characterization of TDRD1 functions in prostate cancer development and suggests TDRD1 as a potential therapeutic target for prostate cancer treatment.

SMN post-translational modifications in spinal muscular atrophy.

Since its first identification as the gene responsible for spinal muscular atrophy (SMA), the range of survival motor neuron (SMN) protein functions has increasingly expanded. This multimeric complex plays a crucial role in a variety of RNA processing pathways. While its most characterized function is in the biogenesis of ribonucleoproteins, several studies have highlighted the SMN complex as an important contributor to mRNA trafficking and translation, axonal transport, endocytosis, and mitochondria metabolism. All these multiple functions need to be selectively and finely modulated to maintain cellular homeostasis. SMN has distinct functional domains that play a crucial role in complex stability, function, and subcellular distribution. Many different processes were reported as modulators of the SMN complex activities, although their contribution to SMN biology still needs to be elucidated. Recent evidence has identified post-translational modifications (PTMs) as a way to regulate the pleiotropic functions of the SMN complex. These modifications include phosphorylation, methylation, ubiquitination, acetylation, sumoylation, and many other types. PTMs can broaden the range of protein functions by binding chemical moieties to specific amino acids, thus modulating several cellular processes. Here, we provide an overview of the main PTMs involved in the regulation of the SMN complex with a major focus on the functions that have been linked to SMA pathogenesis.

FANCI is Associated with Poor Prognosis and Immune Infiltration in Liver Hepatocellular Carcinoma.

Objective: This study aimed to validate FANCI as a potential marker for both prognosis and therapy in liver hepatocellular carcinoma. Method: FANCI expression data were acquired from GEPIA, HPA, TCGA, and GEO databases. The impact of clinicopathological features was analyzed by UALCAN. The prognosis of Liver Hepatocellular Carcinoma (LIHC) patients with highly expressed FANCI was constructed utilizing Kaplan-Meier Plotter. GEO2R was employed to identify differentially expressed genes (DEGs). Metascape was used to analyze functional pathways correlations. Protein-Protein interaction (PPI) networks were generated by Cytoscape. Furthermore, molecular complex detection (MCODE) was utilized to recognize Hub genes, which were selected to establish a prognostic model. Lastly, the relationship between FANCI and immune cell infiltration in LIHC was examined. Results: Compared to adjacent tissues, FANCI expression levels were significantly higher in LIHC tissues and were positively correlated to the cancer grade, stage, and prior hepatitis B virus (HBV) infection. High expression of FANCI was found to be associated with poor prognosis in LIHC (HR=1.89, p<0.001). DEGs that were positively correlated with FANCI were involved in various processes, including the cell cycle, VEGF pathway, immune system processes, and biogenesis of ribonucleoproteins. MCM10, TPX2, PRC1, and KIF11 were identified as key genes closely related to FANCI and poor prognosis. A reliable five-variable prognostic model was constructed with strong predictive capability. Lastly, a positive correlation was observed between FANCI expression and tumor-infiltration levels of CD8+ T cells, B cells, regulatory T (Tregs), CD4+ T helper 2 (Th2), and macrophage M2 cells. Conclusion: FANCI may hold promise as a potential biomarker for predicting prognostic outcomes, and a valuable therapeutic target for LIHC patients, with a focus on anti-proliferation, anti-chemoresistance, and combination with immunotherapy.

Survival motor neuron protein and neurite degeneration are regulated by Gemin3 in spinal muscular atrophy motoneurons.

Spinal Muscular Atrophy (SMA) is a genetic neuromuscular disorder caused by reduction of the ubiquitously expressed protein Survival Motor Neuron (SMN). Low levels of SMN impact on spinal cord motoneurons (MNs) causing their degeneration and progressive muscle weakness and atrophy. To study the molecular mechanisms leading to cell loss in SMN-reduced MNs, we analyzed the NF-κB intracellular pathway in SMA models. NF-κB pathway activation is required for survival and regulates SMN levels in cultured MNs. Here we describe that NF-κB members, inhibitor of kappa B kinase beta (IKKβ), and RelA, were reduced in SMA mouse and human MNs. In addition, we observed that Gemin3 protein level was decreased in SMA MNs, but not in non-neuronal SMA cells. Gemin3 is a core member of the SMN complex responsible for small nuclear ribonucleoprotein biogenesis, and it regulates NF-κB activation through the mitogen-activated protein kinase TAK1. Our experiments showed that Gemin3 knockdown reduced SMN, IKKβ, and RelA protein levels, and caused significant neurite degeneration. Overexpression of SMN increased Gemin3 protein in SMA MNs, but did not prevent neurite degeneration in Gemin3 knockdown cells. These data indicated that Gemin3 reduction may contribute to cell degeneration in SMA MNs.

Prp43/DHX15 exemplify RNA helicase multifunctionality in the gene expression network.

Dynamic regulation of RNA folding and structure is critical for the biogenesis and function of RNAs and ribonucleoprotein (RNP) complexes. Through their nucleotide triphosphate-dependent remodelling functions, RNA helicases are key modulators of RNA/RNP structure. While some RNA helicases are dedicated to a specific target RNA, others are multifunctional and engage numerous substrate RNAs in different aspects of RNA metabolism. The discovery of such multitasking RNA helicases raises the intriguing question of how these enzymes can act on diverse RNAs but also maintain specificity for their particular targets within the RNA-dense cellular environment. Furthermore, the identification of RNA helicases that sit at the nexus between different aspects of RNA metabolism raises the possibility that they mediate cross-regulation of different cellular processes. Prominent and extensively characterized multifunctional DEAH/RHA-box RNA helicases are DHX15 and its Saccharomyces cerevisiae (yeast) homologue Prp43. Due to their central roles in key cellular processes, these enzymes have also served as prototypes for mechanistic studies elucidating the mode of action of this type of enzyme. Here, we summarize the current knowledge on the structure, regulation and cellular functions of Prp43/DHX15, and discuss the general concept and implications of RNA helicase multifunctionality.

Distinct nuclear and cytoplasmic assemblies and interactomes of the mammalian CTLH E3 ligase complex.

The C-terminal to LisH (CTLH) complex is a newly discovered multi-subunit E3 ubiquitin ligase and its cellular functions are poorly characterized. Although some CTLH subunits have been found to localize in both the nucleus and cytoplasm of mammalian cells, differences between the compartment-specific complexes have not been explored. Here, we show that the CTLH complex forms different molecular mass complexes in nuclear and cytoplasmic fractions. Loss of WDR26 severely decreased nuclear CTLH complex subunit levels and impaired higher-order CTLH complex formation, revealing WDR26 as a critical determinant of the nuclear stability of the CTLH complex. Through affinity purification coupled to mass spectrometry of endogenous RanBPM (also called RANBP9), a CTLH complex member, from nuclear and cytoplasmic fractions, we identified over 170 compartment-specific interactors involved in various conserved biological processes, such as ribonucleoprotein biogenesis and chromatin assembly. We validated the nuclear-specific RanBPM interaction with macroH2A1 and the cytoplasm-specific interaction with tankyrase-1/2 (encoded by TNKS and TNKS2). Overall, this study provides critical insights into CTLH complex function and composition in both the cytoplasm and nucleus.

Identification of Signaling Pathways and Phase Separating Domains that Drive Cajal Body Formation

Cajal bodies (CBs) are membraneless subnuclear domains that contribute to the biogenesis and maturation of ribonucleoproteins (RNPs) which take part in fundamental cellular activities such as translation, pre‐mRNA splicing, and telomere maintenance. Partitioning of CBs occurs through liquid‐liquid phase separation (LLPS) where the CB marker protein, coilin, is thought to scaffold the CB. However, the formation of CBs and the regulation of CB number has not been fully elucidated. Disease states such as cancer and preeclampsia have altered CB expression, thus additional insight into CB condensation would provide an important cellular model system that could be used to investigate these and other diseases. We hypothesize that the post‐translational modification (PTM) of coilin regulates CB formation and number by influencing the LLPS of coilin via residues in its intrinsically disordered region (IDR). Here we show, for the first time, a cycloheximide inducible model of CB formation in fibroblasts without increasing coilin concentration. We are also able to induce CB formation by inhibiting kinase GSK3β with indirubin, as well as abolish CB formation by inhibiting phosphatases PP1 and PP2A with okadaic acid. Lastly, we have identified two phase‐separating domains in coilin’s IDR using the phase separation predicting software ParSe. Deletion of each domain prevents CB formation in HeLa cells but does not prevent coilin’s self‐interaction. Collectively, these data will be able to help us understand the role of coilin’s scaffolding capabilities via LLPS mediated CB condensation, as well as provide an important cellular model system that can be used to investigate CB functionality in disease states where CB formation is dysregulated.

Coilin Modulates Nuclear Organization by Promoting Protein SUMOylation

Coilin was first identified as the marker protein for Cajal Bodies (CBs). However, CBs are only abundant in neuronal, embryonic, and cancer cells, while primary cells have few CBs. Even in cells with CBs, 70% of coilin is nucleoplasmic, not found in CBs. CBs are subnuclear domains that function in small nuclear ribonucleoprotein (snRNP) biogenesis as well as production of telomerase RNP, expression and 3’end processing of small nuclear RNAs (snRNAs), small nucleolar RNAs (snoRNAs), and small CB‐associated RNAs (scaRNAs). The function of nucleoplasmic coilin is not well understood. We have previously shown that coilin promotes miRNA biogenesis by promoting phosphorylation of the Microprocessor component, DGCR8, at its S377 residue in both cells with and without CBs. We have since identified 7 additional serine residues of DGCR8 with decreased phosphorylation in coilin knockdown through phosphoproteomic analysis of HeLa cells. In addition to phosphorylation, the addition of a small ubiquitin‐like modifier (SUMO), or SUMOylation, of DGCR8 also increases its stability. Because of coilin’s role in the promotion of one post‐translational modification, here we aimed to test the hypothesis that coilin knockdown alters protein SUMOylation and results in altered nuclear organization. We conducted a series of siRNA knockdowns, Western blots, and immunoprecipitation experiments. Here we show, for the first time, that coilin knockdown results in global decrease of protein SUMOylation in cells with (HeLa) and without CBs (WI‐38), suggesting that regulation of protein SUMOylation may be a function of nucleoplasmic coilin. Specifically, we found that coilin knockdown results in decreased SUMOylation of DGCR8 and Speckled protein 100kDa (Sp100), a major component of the promyelocytic leukemia nuclear body (PML‐NB). Sp100 is vital to PML‐NB formation, and decreased SUMOylation of Sp100 decreases its stability. This information led us to the second part of our hypothesis. We used immunofluorescence and found that coilin knockdown results in decreased numbers of PML‐NBs per cell. To summarize, we have identified coilin as a regulator of protein phosphorylation, SUMOylation, and nuclear organization.

Telomerase holoenzymes

Telomerase is unusual genome replication machinery. The eukaryotic reverse transcriptase ribonucleoprotein (RNP) supplements telomeric simple‐sequence repeat tracts at chromosome ends by new repeat synthesis. Using each chromosome 3’ end as primer and an internal region of the integral telomerase RNA subunit as template, telomerase reiteratively reverse transcribes its short template into tandem single‐stranded telomeric repeats. Lagging‐strand DNA replication machinery and processing enzymes then create the functional telomere structure of duplex repeats with a 3’ overhang that can be single‐stranded, form alternative DNA structures such as G‐quadruplex, or invade the duplex region to form a displacment loop (D‐loop) of telomeric repeats termed the t‐loop.Two and a half decades of research in the Collins lab led the way to a resolution for several puzzles that were facing the telomere and telomerase field since soon after telomerase discovery by Carol Greider and Elizabeth Blackburn. How do telomerase reverse transcriptase protein (TERT) and telomerase RNA co‐fold in a hierarchical, complex process of cellular telomerase RNP biogenesis, and how does this drastically limit the amount of telomerase made by even the most strongly telomerase‐positive human cancer and stem cells? How can a precisely defined region within telomerase RNA be used as template? How does the template‐product duplex unpair and reform in a different template register to enable processive repeat synthesis? How is telomerase brought to telomeres and how does each telomere control telomerase activity according to its individual length to generate telomere length homeostasis?Human telomerase RNA (hTR) relies on proteins shared with H/ACA‐family small nucleolar RNAs for its processing, stability, and assembly with TERT. Inherited and spontaneous mutations in these H/ACA proteins cause disease syndromes by reducing telomerase function, as do subsequently identified mutations in hTR and TERT. Understanding of how these mutations compromise telomerase function has emerged from new high‐resolution structures of telomerase holoenzymes from the ciliate Tetrahymena thermophila and human cells, the two model systems of Collins lab research, and from understanding control of telomerase function at telomeres.

RNA at the surface of phase-separated condensates impacts their size and number

Although it is now recognized that specific RNAs and protein families are critical for the biogenesis of ribonucleoprotein (RNP) condensates, how these molecular constituents determine condensate size and morphology is unknown. To circumvent the biochemical complexity of endogenous RNP condensates, the use of programmable tools to reconstitute condensate formation with minimal constituents can be instrumental. Here we report a methodology to form RNA-containing condensates in living cells programmed to specifically recruit a single RNA species. Our bioengineered condensates are made of ArtiGranule scaffolds composed of an orthogonal protein that can bind to a specific heterologously expressed RNA. These scaffolds undergo liquid-liquid phase separation in cells and can be chemically controlled to prevent condensation or to trigger condensate dissolution. We found that the targeted RNAs localize at the condensate surface, either as isolated RNA molecules or as a homogenous corona of RNA molecules around the condensate. The recruitment of RNA changes the material properties of condensates by hardening the condensate body. Moreover, the condensate size scales with RNA surface density; the higher the RNA density is, the smaller and more frequent the condensates are. These results suggest a mechanism based on physical constraints, provided by RNAs at the condensate surface, that limit condensate growth and coalescence.

Emerging roles of DNA topoisomerases in the regulation of R-loops

R-loops are comprised of a DNA:RNA hybrid and a displaced single-strand DNA (ssDNA) that reinvades the DNA duplex behind the moving RNA polymerase. Because they have several physiological functions within the cell, including gene expression, chromosomal segregation, and mitochondrial DNA replication, among others, R-loop homeostasis is tightly regulated to ensure normal functioning of cellular processes. Thus, several classes of enzymes including RNases, helicases, topoisomerases, as well as proteins involved in splicing and the biogenesis of messenger ribonucleoproteins, have been implicated in R-loop prevention, suppression, and resolution. There exist six topoisomerase enzymes encoded by the human genome that function to introduce transient DNA breaks to relax supercoiled DNA. In this mini-review, we discuss functions of DNA topoisomerases and their emerging role in transcription, replication, and regulation of R-loops, and we highlight how their role in maintaining genome stability can be exploited for cancer therapy.

Spinal Muscular Atrophy Patient iPSC-Derived Motor Neurons Display Altered Proteomes at Early Stages of Differentiation.

Spinal muscular atrophy (SMA) is an autosomal recessive neurodegenerative disorder characterized by loss of motor neurons (MN) in the spinal cord leading to progressive muscle atrophy and weakness. SMA is caused by mutations in the survival motor neuron 1 (SMN1) gene, resulting in reduced levels of survival motor neuron (SMN) protein. The mechanisms that link SMN deficiency to selective motor neuron dysfunction in SMA remain largely unknown. We present here, for the first time, a comprehensive quantitative TMT-10plex proteomics analysis that covers the development of induced pluripotent stem cell-derived MNs from both healthy individuals and SMA patients. We show that the proteomes of SMA samples segregate from controls already at early stages of neuronal differentiation. The altered proteomic signature in SMA MNs is associated with mRNA splicing, ribonucleoprotein biogenesis, organelle organization, cellular biogenesis, and metabolic processes. We highlight several known SMN-binding partners and evaluate their expression changes during MN differentiation. In addition, we compared our study to human and mouse in vivo proteomic studies revealing distinct and similar signatures. Altogether, our work provides a comprehensive resource of molecular events during early stages of MN differentiation, containing potentially therapeutically interesting protein expression profiles for SMA.

Pathogenic variants in the survival of motor neurons complex gene GEMIN5 cause cerebellar atrophy.

Cerebellar ataxia is a genetically heterogeneous disorder. GEMIN5 encoding an RNA-binding protein of the survival of motor neuron complex, is essential for small nuclear ribonucleoprotein biogenesis, and it was recently reported that biallelic loss-of-function variants cause neurodevelopmental delay, hypotonia, and cerebellar ataxia. Here, whole-exome analysis revealed compound heterozygous GEMIN5 variants in two individuals from our cohort of 162 patients with cerebellar atrophy/hypoplasia. Three novel truncating variants and one previously reported missense variant were identified: c.2196dupA, p.(Arg733Thrfs*6) and c.1831G > A, p.(Val611Met) in individual 1, and c.3913delG, p.(Ala1305Leufs*14) and c.4496dupA, p.(Tyr1499*) in individual 2. Western blotting analysis using lymphoblastoid cell lines derived from both affected individuals showed significantly reduced levels of GEMIN5 protein. Zebrafish model for null variants p.(Arg733Thrfs*6) and p.(Ala1305Leufs*14) exhibited complete lethality at 2 weeks and recapitulated a distinct dysplastic phenotype. The phenotypes of affected individuals and the zebrafish mutant models strongly suggest that biallelic loss-of-function variants in GEMIN5 cause cerebellar atrophy/hypoplasia.

Assembly of higher-order SMN oligomers is essential for metazoan viability and requires an exposed structural motif present in the YG zipper dimer.

Protein oligomerization is one mechanism by which homogenous solutions can separate into distinct liquid phases, enabling assembly of membraneless organelles. Survival Motor Neuron (SMN) is the eponymous component of a large macromolecular complex that chaperones biogenesis of eukaryotic ribonucleoproteins and localizes to distinct membraneless organelles in both the nucleus and cytoplasm. SMN forms the oligomeric core of this complex, and missense mutations within its YG box domain are known to cause Spinal Muscular Atrophy (SMA). The SMN YG box utilizes a unique variant of the glycine zipper motif to form dimers, but the mechanism of higher-order oligomerization remains unknown. Here, we use a combination of molecular genetic, phylogenetic, biophysical, biochemical and computational approaches to show that formation of higher-order SMN oligomers depends on a set of YG box residues that are not involved in dimerization. Mutation of key residues within this new structural motif restricts assembly of SMN to dimers and causes locomotor dysfunction and viability defects in animal models.

The Cajal body protein coilin is a regulator of the miR-210 hypoxamiR and influences MIR210HG alternative splicing.

Hypoxia is a severe stressor to cellular homeostasis. At the cellular level, low oxygen triggers the transcription of a variety of genes supporting cell survival and oxygen homeostasis mediated by transcription factors, such as hypoxia-inducible factors (HIFs). Among many determinants dictating cell responses to hypoxia and HIFs are microRNAs (miRNAs). Cajal bodies (CBs), subnuclear structures involved in ribonucleoprotein biogenesis, have been recently proven to contribute to miRNA processing and biogenesis but have not been studied under hypoxia. Here, we show, for the first time, a hypoxia-dependent increase in CB number in WI-38 primary fibroblasts, which normally have very few CBs. Additionally, the CB marker protein coilin is upregulated in hypoxic WI-38 cells. However, the hypoxic coilin upregulation was not seen in transformed cell lines. Furthermore, we found that coilin is needed for the hypoxic induction of a well-known hypoxia-induced miRNA (hypoxamiR), miR-210, as well as for the hypoxia-induced alternative splicing of the miR-210 host gene, MIR210HG. These findings provide a new link in the physiological understanding of coilin, CBs and miRNA dysregulation in hypoxic pathology.

An autoantigen profile of human A549 lung cells reveals viral and host etiologic molecular attributes of autoimmunity in COVID-19

We aim to establish a comprehensive COVID-19 autoantigen atlas in order to understand autoimmune diseases caused by SARS-CoV-2 infection. Based on the unique affinity between dermatan sulfate and autoantigens, we identified 348 proteins from human lung A549 cells, of which 198 are known targets of autoantibodies. Comparison with current COVID data identified 291 proteins that are altered at protein or transcript level in SARS-CoV-2 infection, with 191 being known autoantigens. These known and putative autoantigens are significantly associated with viral replication and trafficking processes, including gene expression, ribonucleoprotein biogenesis, mRNA metabolism, translation, vesicle and vesicle-mediated transport, and apoptosis. They are also associated with cytoskeleton, platelet degranulation, IL-12 signaling, and smooth muscle contraction. Host proteins that interact with and that are perturbed by viral proteins are a major source of autoantigens. Orf3 induces the largest number of protein alterations, Orf9 affects the mitochondrial ribosome, and they and E, M, N, and Nsp proteins affect protein localization to membrane, immune responses, and apoptosis. Phosphorylation and ubiquitination alterations by viral infection define major molecular changes in autoantigen origination. This study provides a large list of autoantigens as well as new targets for future investigation, e.g., UBA1, UCHL1, USP7, CDK11A, PRKDC, PLD3, PSAT1, RAB1A, SLC2A1, platelet activating factor acetylhydrolase, and mitochondrial ribosomal proteins. This study illustrates how viral infection can modify host cellular proteins extensively, yield diverse autoantigens, and trigger a myriad of autoimmune sequelae. Our work provides a rich resource for studies into “long COVID” and related autoimmune sequelae.

MRE11 Is Crucial for Malaria Parasite Transmission and Its Absence Affects Expression of Interconnected Networks of Key Genes Essential for Life.

The meiotic recombination 11 protein (MRE11) plays a key role in DNA damage response and maintenance of genome stability. However, little is known about its function during development of the malaria parasite Plasmodium. Here, we present a functional, ultrastructural and transcriptomic analysis of Plasmodium parasites lacking MRE11 during its life cycle in both mammalian and mosquito vector hosts. Genetic disruption of Plasmodium berghei mre11 (PbMRE11) results in significant retardation of oocyst development in the mosquito midgut associated with cytoplasmic and nuclear degeneration, along with concomitant ablation of sporogony and subsequent parasite transmission. Further, absence of PbMRE11 results in significant transcriptional downregulation of genes involved in key interconnected biological processes that are fundamental to all eukaryotic life including ribonucleoprotein biogenesis, spliceosome function and iron–sulfur cluster assembly. Overall, our study provides a comprehensive functional analysis of MRE11′s role in Plasmodium development during the mosquito stages and offers a potential target for therapeutic intervention during malaria parasite transmission.

Folding heterogeneity in the essential human telomerase RNA three-way junction.

Telomeres safeguard the genome by suppressing illicit DNA damage responses at chromosome termini. To compensate for incomplete DNA replication at telomeres, most continually dividing cells, including many cancers, express the telomerase ribonucleoprotein (RNP) complex. Telomerase maintains telomere length by catalyzing de novo synthesis of short DNA repeats using an internal telomerase RNA (TR) template. TRs from diverse species harbor structurally conserved domains that contribute to RNP biogenesis and function. In vertebrate TRs, the conserved regions 4 and 5 (CR4/5) fold into a three-way junction (TWJ) that binds directly to the telomerase catalytic protein subunit and is required for telomerase function. We have analyzed the structural properties of the human TR (hTR) CR4/5 domain using a combination of in vitro chemical mapping, secondary structural modeling, and single-molecule structural analysis. Our data suggest the essential P6.1 stem–loop within CR4/5 is not stably folded in the absence of the telomerase reverse transcriptase in vitro. Rather, the hTR CR4/5 domain adopts a heterogeneous ensemble of conformations. Finally, single-molecule FRET measurements of CR4/5 and a mutant designed to stabilize the P6.1 stem demonstrate that TERT binding selects for a structural conformation of CR4/5 that is not the dominant state of the TERT-free in vitro RNA ensemble.

The Impact of Coilin Nonsynonymous SNP Variants E121K and V145I on Cell Growth and Cajal Body Formation: The First Characterization.

Coilin is the main component of Cajal body (CB), a membraneless organelle that is involved in the biogenesis of ribonucleoproteins and telomerase, cell cycle, and cell growth. The disruption of CBs is linked to neurodegenerative diseases and potentially cancers. The coilin gene (COIL) contains two nonsynonymous SNPs: rs116022828 (E121K) and rs61731978 (V145I). Here, we investigated for the first time the functional impacts of these coilin SNPs on CB formation, coilin subcellular localization, microtubule formation, cell growth, and coilin expression and protein structure. We revealed that both E121K and V145I mutants could disrupt CB formation and result in various patterns of subcellular localization with survival motor neuron protein. Noteworthy, many of the E121K cells showed nucleolar coilin accumulation. The microtubule regrowth and cell cycle assays indicated that the E121K cells appeared to be trapped in the S and G2/M phases of cell cycle, resulting in reduced cell proliferation. In silico protein structure prediction suggested that the E121K mutation caused greater destabilization on the coilin structure than the V145I mutation. Additionally, clinical bioinformatic analysis indicated that coilin expression levels could be a risk factor for cancer, depending on the cancer types and races.