Cytochrome c oxidase deficiency detection in human fibroblasts using scanning electrochemical microscopy.

Cytochrome c oxidase deficiency (COXD) is an inherited disorder characterized by the absence or mutation in the genes encoding for the cytochrome c oxidase protein (COX). COX deficiency results in severe muscle weakness, heart, liver, and kidney disorders, as well as brain damage in infants and adolescents, leading to death in many cases. With no cure for this disorder, finding an efficient, inexpensive, and early means of diagnosis is essential to minimize symptoms and long-term disabilities. Furthermore, muscle biopsy, the traditional detection method, is invasive, expensive, and time-consuming. This study demonstrates the applicability of scanning electrochemical microscopy to quantify COX activity in living human fibroblast cells. Taking advantage of the interaction between the redox mediator N, N, N', N'-tetramethyl-para-phenylene-diamine, and COX, the enzymatic activity was successfully quantified by monitoring current changes using a platinum microelectrode and determining the apparent heterogeneous rate constant k0 using numerical modeling. This study provides a foundation for developing a diagnostic method for detecting COXD in infants, which has the potential to increase treatment effectiveness and improve the quality of life of affected individuals.

Nuclear SRP9/SRP14 heterodimer transcriptionally regulates 7SL and BC200 RNA expression.

The SRP9/SRP14 heterodimer is a central component of signal recognition particle (SRP) RNA (7SL) processing and Alu retrotransposition. In this study, we sought to establish the role of nuclear SRP9/SRP14 in the transcriptional regulation of 7SL and BC200 RNA. 7SL and BC200 RNA steady-state levels, rate of decay, and transcriptional activity were evaluated under SRP9/SRP14 knockdown conditions. Immunofluorescent imaging, and subcellular fractionation of MCF-7 cells, revealed a distinct nuclear localization for SRP9/SRP14. The relationship between this localization and transcriptional activity at 7SL and BC200 genes was also examined. These findings demonstrate a novel nuclear function of SRP9/SRP14 establishing that this heterodimer transcriptionally regulates 7SL and BC200 RNA expression. We describe a model in which SRP9/SRP14 cotranscriptionally regulate 7SL and BC200 RNA expression. Our model is also a plausible pathway for regulating Alu RNA transcription and is consistent with the hypothesized roles of SRP9/SRP14 transporting 7SL RNA into the nucleolus for posttranscriptional processing, and trafficking of Alu RNA for retrotransposition.

Distinct domain organization and diversity of 2'-5'-oligoadenylate synthetases.

The 2'-5'-oligoadenylate synthetases (OAS) are important components of the innate immune system that recognize viral double-stranded RNA (dsRNA). Upon dsRNA binding, OAS generate 2'-5'-linked oligoadenylates (2-5A) that activate ribonuclease L (RNase L), halting viral replication. The OAS/RNase L pathway is thus an important antiviral pathway and viruses have devised strategies to circumvent OAS activation. OAS enzymes are divided into four classes according to size: small (OAS1), medium (OAS2), and large (OAS3) that consist of one, two, and three OAS domains, respectively, and the OAS-like protein (OASL) that consists of one OAS domain and tandem domains similar to ubiquitin. Early investigation of the OAS enzymes hinted at the recognition of dsRNA by OAS, but due to size differences amongst OAS family members combined with the lack of structural information on full-length OAS2 and OAS3, the regulation of OAS catalytic activity by dsRNA was not well understood. However, the recent biophysical studies of OAS have highlighted overall structure and domain organization. In this review, we present a detailed examination of the OAS literature and summarized the investigation on 2'-5'-oligoadenylate synthetases.

Promoting physical activity in rheumatoid arthritis through a physiotherapist led behaviour change-based intervention (PIPPRA): a feasibility randomised trial.

Physical activity (PA) is recommended as a key component in the management of people with rheumatoid arthritis (RA). The objective of this study was to examine the feasibility of a physiotherapist led, behaviour change (BC) theory-informed, intervention to promote PA in people with RA who have low levels of current PA. A feasibility randomised trial (ClinicalTrials.gov NCT03644160) of people with RA over 18 years recruited from outpatient rheumatology clinics and classified as insufficiently physically active using the Godin-Shephard Leisure Time Physical Activity Questionnaire. Participants were randomised to intervention group (4 BC physiotherapy sessions in 8 weeks) delivered in person/virtually or control group (PA information leaflet only). Feasibility targets (eligibility, recruitment, and refusal), protocol adherence and acceptability were measured. Health care professionals (HCPs) involved in the study and patients in the intervention and control arms were interviewed to determine acceptability. Descriptive statistics were used to analyse the data with SPSS (v27) with interviews analysed using content analysis using NVivo (v14). Three hundred and twenty participants were identified as potentially eligible, with n = 183 (57%) eligible to participate, of which n = 58 (32%) consented to participate. The recruitment rate was 6.4 per month. Due to the impact of COVID-19 on the study, recruitment took place over two separate phases in 2020 and 2021. Of the 25 participants completing the full study, 23 were female (mean age 60 years (SD 11.5)), with n = 11 allocated to intervention group and n = 14 to control. Intervention group participants completed 100% of sessions 1 & 2, 88% of session 3 and 81% of session 4. The study design and intervention were acceptable overall to participants, with enhancements suggested. The PIPPRA study to improve promote physical activity in people with RA who have low PA levels was feasible, acceptable and safe. Despite the impact of COVID-19 on the recruitment and retention of patients, the study provides preliminary evidence that this physiotherapist led BC intervention is feasible and a full definitive intervention should be undertaken. Health care professionals involved in the study delivery and the patient participants described a number of positive aspects to the study with some suggestions to enhance the design. These findings hence inform the design of a future efficacy-focused clinical trial.

Supportive Housing for Sexual and Gender Minority Individuals with Criminal Justice Histories: Challenges and Opportunities Identified by Providers and Clients.

Sexual and gender minority (SGM) individuals experience high rates of homelessness and criminal justice system involvement, underscoring the need for supportive housing services. To explore the service needs of this population, we interviewed providers (n = 11) and clients (n = 10) from eight supportive housing organizations working with SGM populations in Los Angeles County, USA. We used the Consolidated Framework for Implementation Research to synthesize interview responses into themes (by domain and cross-cutting). Take-aways included the need for investment in systems of care for vulnerable SGM populations; the particular marginalization of Trans individuals and providers that serve them; the roles of supportive housing staff, residents, and leadership in cultivating an affirming environment; prevalence of discrimination and stigma within supportive housing programs and broader society; and the complex interrelationships among SGM identity, homelessness, and criminal justice system involvement. These findings have important implications for supportive housing services and related policy.

Photoactive monofunctional platinum(II) anticancer complexes of multidentate phenanthridine-containing ligands: photocytotoxicity and evidence for interaction with DNA.

Pt(II) complexes supported by chelating, multidentate ligands containing π-extended, planar phenanthridine (benzo[c]quinoline) donors (RLPtCl) exhibit a promising in vitro therapeutic index compared with phenanthriplatin, a leading preclinical anticancer complex containing a monodentate phenanthridine ligand. Here, we report evidence for non-specific interactions of CF3LPtCl with DNA through intercalation-mediated turn-on luminescence in O2-saturated aqueous buffer. Brief irradiation with visible light (490 nm) was also found to drastically increase the activity of CF3LPtCl, with photocytotoxicity increased up to 87% against a variety of human cancer cell lines. Mechanistic studies highlight significantly improved cellular uptake of CF3LPtCl compared with cisplatin, with localization in the nucleus and mitochondria triggering effective apoptosis. Photosensitization experiments with 1,3-diphenylisobenzofuran demonstrate that CF3LPtCl efficiently mediates the generation of singlet dioxygen (1O2), highlighting the potential of RLPtCl in photodynamic therapy.

'I learnt so much about being active': experiences of people with rheumatoid arthritis on the impact of a physiotherapist-led intervention to encourage physical activity.

INTRODUCTION: Physical activity (PA) is an important component in improving the health of people with rheumatoid arthritis (RA). A Physiotherapist-led Intervention to Promote PA in people with RA (PIPPRA) was undertaken using the Behaviour Change (BC) Wheel. A qualitative study was conducted post intervention involving participants and healthcare professionals who participated in a pilot RCT. METHODS: Face-to-face semi-structured interviews were conducted with the schedule exploring: experience and views of the intervention; experience and suitability of outcome measures used; and perceptions of BC and PA. Thematic analysis was used as an analytical approach. The COREQ checklist provided guidance throughout. RESULTS: Fourteen participants and eight healthcare staff participated. Three main themes were generated from participants: (1) positive experience of intervention - 'I found it very knowledgeable to help me get stronger'; (2) improvement in self-management - '… motivate me maybe to go back to doing a little bit more exercise'; and (3) negative impact of COVID-19 - 'I don't think doing it online again would be really good at all'. Two main themes were generated from healthcare professionals: (1) positive learning experience of delivery - 'Really made me realise the importance of discussing physical activity with patients'; and (2) positive approach to recruitment - 'Very professional team showing the importance of having a study member on site'. DISCUSSION: Participants had a positive experience of being involved in a BC intervention in order to improve their PA and found it acceptable as an intervention. Healthcare professionals also had a positive experience, in particular the importance of recommending PA in empowering patients.

Feasibility of a physiotherapist-led behaviour change intervention to improve physical activity in people with rheumatoid arthritis.

INTRODUCTION: Physical activity (PA) interventions incorporating behaviour change (BC) theory are needed to improve PA levels in people with rheumatoid arthritis. A pilot feasibility study of a Physiotherapist-led Intervention to Promote PA in Rheumatoid Arthritis (PIPPRA) was undertaken to obtain estimates for recruitment rate, participant retention and protocol adherence. METHODS: Participants were recruited at University Hospital (UH) rheumatology clinics and randomly assigned to control group (physical activity information leaflet) or intervention group (four BC physiotherapy sessions in 8 weeks). Inclusion criteria were diagnosis of RA (ACR/EULAR 2010 classification criteria), aged 18+ years and classified as insufficiently physically active. Ethical approval was obtained from the UH research ethics committee. Participants were assessed at baseline (T0), 8 weeks (T1) and 24 weeks (T2). Descriptive statistics and t-tests were used to analyse the data with SPSS v22. RESULTS: 320 participants were approached about the study with n=183 (57%) eligible to participate and n=58 (55%) consented to participate (recruitment rate: 6.4 per month; refusal rate 59%). Due to the impact of COVID-19 on the study, n=25 (43%) participants completed the study (n=11 (44%) intervention and n=14 (56%) control). Of the 25, n=23 (92%) were female, mean age was 60 years (s.d. 11.5). Intervention group participants completed 100% of BC sessions 1 and 2, 88% completed session 3 and 81% completed session 4. DISCUSSION: The intervention to promote physical activity was feasible and safe and provides a framework for larger intervention studies. Based on these findings, a fully powered trial is recommended.

The noncoding RNA BC200 associates with polysomes to positively regulate mRNA translation in tumor cells.

BC200 is a noncoding RNA elevated in a broad spectrum of tumor cells that is critical for cell viability, invasion, and migration. Overexpression studies have implicated BC200 and the rodent analog BC1 as negative regulators of translation in both cell-based and in vitro translation assays. Although these studies are consistent, they have not been confirmed in knockdown studies and direct evidence for this function is lacking. Herein, we have demonstrated that BC200 knockdown is correlated with a decrease in global translation rates. As this conflicts with the hypothesis that BC200 is a translational suppressor, we overexpressed BC200 by transfection of in vitro transcribed RNA and transient expression from transfected plasmids. In this context BC200 suppressed translation; however, an innate immune response confounded the data. To overcome this, breast cancer cells stably overexpressing BC200 and various control RNAs were developed by selection for genomic incorporation of a plasmid coexpressing BC200 and the neomycin resistance gene. Stable overexpression of BC200 was associated with elevated translation levels in pooled stable cell lines and isolated single-cell clones. Cross-linking sucrose density gradient centrifugation demonstrated an association of BC200 and its reported binding partners SRP9/14, CSDE1, DHX36, and PABPC1 with both ribosomal subunits and polysomal RNA, an association not previously observed owing to the labile nature of the interactions. In summary, these data present a novel understanding of BC200 function as well as optimized methodology that has far reaching implications in the study of noncoding RNAs, particularly within the context of translational regulatory mechanisms.

An RNA guanine quadruplex regulated pathway to TRAIL-sensitization by DDX21.

DDX21 is a newly discovered RNA G-quadruplex (rG4) binding protein with no known biological rG4 targets. In this study we used label-free proteomic MS/MS to identify 26 proteins that are expressed at significantly different levels in cells expressing an rG4-binding deficient DDX21 (M4). MS data are available via ProteomeXchange with identifier PXD013501. From this list we validate MAGED2 as a protein that is regulated by DDX21 through rG4 in its 5'-UTR. MAGED2 protein levels, but not mRNA levels, are reduced by half in cells expressing DDX21 M4. MAGED2 has a repressive effect on TRAIL-R2 expression that is relieved under these conditions, resulting in elevated TRAIL-R2 mRNA and protein in MCF-7 cells, rendering them sensitive to TRAIL-mediated apoptosis. Our work identifies the role of DDX21 in regulation at the translational level through biologically relevant rG4 and shows that MAGED2 protein levels are regulated, at least in part, by the potential to form rG4 in their 5'-UTRs.

Predicting human RNA quadruplex helicases through comparative sequence approaches and helicase mRNA interactome analyses.

RNA quadruplexes are non-canonical nucleic acid structures involved in several human disease states and are regulated by a specific subset of RNA helicases. Given the difficulty in identifying RNA quadruplex helicases due to the multifunctionality of these enzymes, we sought to provide a comprehensive in silico analysis of features found in validated RNA quadruplex helicases to predict novel human RNA quadruplex helicases. Using the 64 human RNA helicases, we correlated their amino acid compositions with subsets of RNA quadruplex helicases categorized by varying levels of evidence of RNA quadruplex interaction. Utilizing phylogenetic and synonymous/non-synonymous substitution analyses, we identified an evolutionarily conserved pattern involving predicted intrinsic disorder and a previously identified motif. We analyzed available next-generation sequencing data to determine which RNA helicases directly interacted with predicted RNA quadruplex regions intracellularly and elucidated the relationship with miRNA binding sites adjacent to RNA quadruplexes. Finally, we performed a phylogenetic analysis of all 64 human RNA helicases to establish how RNA quadruplex detection and unwinding activity may be conserved among helicase subfamilies. This work furthers the understanding of commonalities between RNA quadruplex helicases and provides support for the future validation of several human RNA helicases.

Alu RNA and their roles in human disease states.

Alu RNA are implicated in the poor prognosis of several human disease states. These RNA are transcription products of primate specific transposable elements called Alu elements. These elements are extremely abundant, comprising over 10% of the human genome, and 100 to 1000 cytoplasmic copies of Alu RNA per cell. Alu RNA do not have a single universal functional role aside from selfish self-propagation. Despite this, Alu RNA have been found to operate in a diverse set of translational and transcriptional mechanisms. This review will focus on the current knowledge of Alu RNA involved in human disease states and known mechanisms of action. Examples of Alu RNA that are transcribed in a variety of contexts such as introns, mature mRNA, and non-coding transcripts will be discussed. Past and present challenges in studying Alu RNA, and the future directions of Alu RNA in basic and clinical research will also be examined.

The feasibility of an exercise intervention to improve sleep (time, quality and disturbance) in people with rheumatoid arthritis: a pilot RCT.

Current rheumatology guidelines recommend exercise as a key component in the management of people with RA, however, what is lacking is evidence on its impact on sleep. Objective is to assess the feasibility of a walking-based intervention on TST, sleep quality, and sleep disturbance and to generate potential effect size estimates for a main trial. Participants were recruited at weekly rheumatology clinics and through social media. Patients with RA were randomized to a walking-based intervention consisting of 28 sessions, spread over 8 weeks (2-5 times/week), with 1 per week being supervised by a physiotherapist, or to a control group who received verbal and written advice on the benefits of exercise. Primary outcomes were recruitment, retention, protocol adherence and participant experience. The study protocol was published and registered in ClinicalTrials.gov NCT03140995. One hundred and one (101) people were identified through clinics, 36 through social media. Of these, 24 met the eligibility criteria, with 20 randomized (18% recruitment; 100% female; mean age 57 (SD 7.3 years). Ten intervention participants (100%) and eight control participants (80%) completed final assessments, with both groups equivalent for all variables at baseline. Participants in the intervention group completed 87.5% of supervised sessions and 93% of unsupervised sessions. No serious adverse events were related to the intervention. Pittsburgh Sleep Quality Index global score showed a significant mean improvement between the exercise group-6.6 (SD 3.3) compared to the control group-0.25 (SD 1.1) (p = 0.012); Intervention was feasible, safe and highly acceptable to study participants, with those participants in the exercise group reporting improvements in sleep duration and sleep quality compared to the control group. Based on these findings, a fully powered randomized trial is recommended. Trial registration number: ClinicalTrials.gov Identifier: NCT03140995 (April 25th, 2017).

Structural and Hydrodynamic Characterization of Dimeric Human Oligoadenylate Synthetase 2.

Oligoadenylate synthetases (OASs) are a family of interferon-inducible enzymes that require double-stranded RNA (dsRNA) as a cofactor. Upon binding dsRNA, OAS undergoes a conformational change and is activated to polymerize ATP into 2'-5'-oligoadenylate chains. The OAS family consists of several isozymes, with unique domain organizations to potentially interact with dsRNA of variable length, providing diversity in viral RNA recognition. In addition, oligomerization of OAS isozymes, potentially OAS1 and OAS2, is hypothesized to be important for 2'-5'-oligoadenylate chain building. In this study, we present the solution conformation of dimeric human OAS2 using an integrated approach involving small-angle x-ray scattering, analytical ultracentrifugation, and dynamic light scattering techniques. We also demonstrate OAS2 dimerization using immunoprecipitation approaches in human cells. Whereas mutation of a key active-site aspartic acid residue prevents OAS2 activity, a C-terminal mutation previously hypothesized to disrupt OAS self-association had only a minor effect on OAS2 activity. Finally, we also present the solution structure of OAS1 monomer and dimer, comparing their hydrodynamic properties with OAS2. In summary, our work presents the first, to our knowledge, dimeric structural models of OAS2 that enhance our understanding of the oligomerization and catalytic function of OAS enzymes.

Impact of double-stranded RNA characteristics on the activation of human 2'-5'-oligoadenylate synthetase 2 (OAS2).

Human 2'-5' oligoadenylate synthetases (OAS) are a family of interferon-inducible proteins that, upon activation by double-stranded RNA, polymerize ATP into 2'-5' linked oligoadenylates. In this study, we probed the RNA cofactor specificity of the two smallest isozymes, OAS1 and OAS2. First, we developed a strategy for the expression and purification of recombinant human OAS2 from eukaryotic cells and quantified the activity of the enzyme relative to OAS1 in vitro. We then confirmed that both OAS2 domains, as opposed to only the domain containing the canonical catalytic aspartic acid triad, are required for enzymatic activity. Enzyme kinetics of both OAS1 and OAS2 in the presence of a variety of RNA binding partners enabled characterization of the maximum reaction velocity and apparent RNA-protein affinity of activating RNAs. While in this study OAS1 can be catalytically activated by dsRNA of any length greater than 19 bp, OAS2 showed a marked increase in activity with increasing dsRNA length with a minimum requirement of 35 bp. Interestingly, activation of OAS2 was also more efficient when the dsRNA contained 3'-overhangs, despite no significant impact on binding affinity. Highly structured viral RNAs that are established OAS1 activators were not able to activate OAS2 enzymatic activity based on the lack of extended stretches of dsRNA of greater than 35 bp. Together these results may highlight distinct subsets of biological RNAs to which different human OAS isozymes respond.

N-alkylated linear heptamethine polyenes as potent non-azole leads against Candida albicans fungal infections.

In this study, eighteen heptamethine dyes were synthesised and their antifungal activities were evaluated against three clinically relevant yeast species.. The eighteen dyes were placed within classes based on their core subunit i.e. 2,3,3-trimethylindolenine (5a-f), 1,1,2-trimethyl-1H-benzo[e]indole (6a-f), or 2-methylbenzothiazole (7a-f). The results presented herein imply that the three families of cyanine dyes, in particular compounds 5a-f, show high potential as selective scaffolds to treat C. albicans infections. This opens up the opportunity for further optimisation and investigation of this class compounds for potential antifungal treatment.

Comprehensive analysis of the BC200 ribonucleoprotein reveals a reciprocal regulatory function with CSDE1/UNR.

BC200 is a long non-coding RNA primarily expressed in brain but aberrantly expressed in various cancers. To gain a further understanding of the function of BC200, we performed proteomic analyses of the BC200 ribonucleoprotein (RNP) by transfection of 3' DIG-labelled BC200. Protein binding partners of the functionally related murine RNA BC1 as well as a scrambled BC200 RNA were also assessed in both human and mouse cell lines. Stringent validation of proteins identified by mass spectrometry confirmed 14 of 84 protein binding partners and excluded eight proteins that did not appreciably bind BC200 in reverse experiments. Gene ontology analyses revealed general roles in RNA metabolic processes, RNA processing and splicing. Protein/RNA interaction sites were mapped with a series of RNA truncations revealing three distinct modes of interaction involving either the 5' Alu-domain, 3' A-rich or 3' C-rich regions. Due to their high enrichment values in reverse experiments, CSDE1 and STRAP were further analyzed demonstrating a direct interaction between CSDE1 and BC200 and indirect binding of STRAP to BC200 via heterodimerization with CSDE1. Knock-down studies identified a reciprocal regulatory relationship between CSDE1 and BC200 and immunofluorescence analysis of BC200 knock-down cells demonstrated a dramatic reorganization of CSDE1 into distinct nuclear foci.

Structure and hydrodynamics of a DNA G-quadruplex with a cytosine bulge.

The identification of four-stranded G-quadruplexes (G4s) has highlighted the fact that DNA has additional spatial organisations at its disposal other than double-stranded helices. Recently, it became clear that the formation of G4s is not limited to the traditional G3+NL1G3+NL2G3+NL3G3+ sequence motif. Instead, the G3 triplets can be interrupted by deoxythymidylate (DNA) or uridylate (RNA) where the base forms a bulge that loops out from the G-quadruplex core. Here, we report the first high-resolution X-ray structure of a unique unimolecular DNA G4 with a cytosine bulge. The G4 forms a dimer that is stacked via its 5'-tetrads. Analytical ultracentrifugation, static light scattering and small angle X-ray scattering confirmed that the G4 adapts a predominantly dimeric structure in solution. We provide a comprehensive comparison of previously published G4 structures containing bulges and report a special γ torsion angle range preferentially populated by the G4 core guanylates adjacent to bulges. Since the penalty for introducing bulges appears to be negligible, it should be possible to functionalize G4s by introducing artificial or modified nucleotides at such positions. The presence of the bulge alters the surface of the DNA, providing an opportunity to develop drugs that can specifically target individual G4s.

Assessment of Different Methods for Pediatric Meningitis Dosing Clinical Decision Support.

BACKGROUND: Indication-specific medication dosing support is needed to improve pediatric dosing support. OBJECTIVE: To compare the sensitivity and positive predictive value (PPV) of different meningitis dosing alert triggers and dosing error rates between antimicrobials with and without meningitis order sentences. METHODS: We retrospectively analyzed 4-months of pediatric orders for antimicrobials with meningitis-specific dosing. At the time of the order, it was determined if the antimicrobial was for meningitis management, if a cerebrospinal fluid (CSF) culture was ordered, and if a natural language processing (NLP) system could detect "meningitis" in clinical notes. RESULTS: Of 1383 orders, 243 were for the management of meningitis. A CSF culture or NLP combination trigger searching the electronic health record since admission yielded the greatest sensitivity for detecting meningitis management (67.5%, P < 0.01 vs others), but dosing error detection was similar if the trigger only searched 48 hours preceding the order (68.8% vs 62.5%, P = 0.125). Using a CSF culture alone and a 48-hour time frame had a higher PPV versus a combination with a 48-hour time frame (97.1% vs 80.9%, P < 0.001), and both triggers had a higher PPV than others ( P < 0.001). Antimicrobials with meningitis order sentences had fewer dosing errors (19.8% vs 43.2%, P < 0.01). Conclusion and Relevance: A meningitis dosing alert triggered by a combination of a CSF culture or NLP system and a 48-hour triggering time frame could provide reasonable sensitivity and PPV for meningitis dosing errors. Order sentences with indication-specific recommendations may provide additional dosing support, but additional studies are needed.

Human DDX21 binds and unwinds RNA guanine quadruplexes.

Guanine quadruplexes (G4s) are an important structure of nucleic acids (DNA and RNA) with roles in several cellular processes. RNA G4s require specialized unwinding enzymes, of which only two have been previously identified. We describe the results of a simple and specific mass spectrometry guided method used to screen HEK293T cell lysate for G4 binding proteins. From these results, we validated the RNA helicase protein DDX21. DDX21 is an established RNA helicase, but has not yet been validated as a G4 binding protein. Through biochemical techniques, we confirm that DDX21-quadruplex RNA interactions are direct and mediated via a site of interaction at the C-terminus of the protein. Furthermore, through monitoring changes in nuclease sensitivity we show that DDX21 can unwind RNA G4. Finally, as proof of principle, we demonstrate the ability of DDX21 to suppress the expression of a protein with G4s in the 3΄ UTR of its mRNA.