Functional link between DEAH/RHA helicase Prp43 activation and ATP base binding

Contrasting functions of ATP hydrolysis by MDA5 and LGP2 in viral RNA sensing

Cytosolic long dsRNA, among the most potent proinflammatory signals, is recognized by melanoma differentiation-associated protein 5 (MDA5). MDA5 binds dsRNA cooperatively forming helical filaments. ATP hydrolysis by MDA5 fulfills a proofreading function by promoting dissociation of shorter endogenous dsRNs from MDA5 while allowing longer viral dsRNAs to remain bound leading to activation of interferon-β responses. Here, we show that adjacent MDA5 subunits in MDA5-dsRNA filaments hydrolyze ATP cooperatively, inducing cooperative filament disassembly. Consecutive rounds of ATP hydrolysis amplify the filament footprint, displacing tightly bound proteins from dsRNA. Our electron microscopy and biochemical assays show that LGP2 binds to dsRNA at internal binding sites through noncooperative ATP hydrolysis. Unlike MDA5, LGP2 has low nucleic acid selectivity and can hydrolyze GTP and CTP as well as ATP. Binding of LGP2 to dsRNA promotes nucleation of MDA5 filament assembly resulting in shorter filaments. Molecular modeling identifies an internally bound MDA5-LGP2-RNA complex, with the LGP2 C-terminal tail forming the key contacts with MDA5. These contacts are specifically required for NTP-dependent internal RNA binding. We conclude that NTPase-dependent binding of LGP2 to internal dsRNA sites complements NTPase-independent binding to dsRNA ends, via distinct binding modes, to increase the number and signaling output of MDA5-dsRNA complexes.

Molecular functions of RNA helicases during ribosomal subunit assembly

During their biogenesis, the ribosomal subunits undergo numerous structural and compositional changes to achieve their final architecture. RNA helicases are a key driving force of such remodelling events but deciphering their particular functions has long been challenging due to lack of knowledge of their molecular functions and RNA substrates. Advances in the biochemical characterisation of RNA helicase activities together with new insights into RNA helicase binding sites on pre-ribosomes and structural snapshots of pre-ribosomal complexes containing RNA helicases now open the door to a deeper understanding of precisely how different RNA helicases contribute to ribosomal subunit maturation.

Structure and function of spliceosomal DEAH-box ATPases

Splicing of precursor mRNAs is a hallmark of eukaryotic cells, performed by a huge macromolecular machine, the spliceosome. Four DEAH-box ATPases are essential components of the spliceosome, which play an important role in the spliceosome activation, the splicing reaction, the release of the spliced mRNA and intron lariat, and the disassembly of the spliceosome. An integrative approach comprising X-ray crystallography, single particle cryo electron microscopy, single molecule FRET, and molecular dynamics simulations provided deep insights into the structure, dynamics and function of the spliceosomal DEAH-box ATPases.

Conformational dynamics of the RNA binding channel regulates loading and translocation of the DEAH-box helicase Prp43

The DEAH-box helicase Prp43 has essential functions in pre-mRNA splicing and ribosome biogenesis, remodeling structured RNAs. To initiate unwinding, Prp43 must first accommodate a single-stranded RNA segment into its RNA binding channel. This allows translocation of the helicase on the RNA. G-patch (gp) factors activate Prp43 in its cellular context enhancing the intrinsically low ATPase and RNA unwinding activity. It is unclear how the RNA loading process is accomplished by Prp43 and how it is regulated by its substrates, ATP and RNA, and the G-patch partners. We developed single-molecule (sm) FRET reporters on Prp43 from Chaetomium thermophilum to monitor the conformational dynamics of the RNA binding channel in Prp43 in real-time. We show that the channel can alternate between open and closed conformations. Binding of Pfa1(gp) and ATP shifts the distribution of states towards channel opening, facilitating the accommodation of RNA. After completion of the loading process, the channel remains firmly closed during successive cycles of ATP hydrolysis, ensuring stable interaction with the RNA and processive translocation. Without Pfa1(gp), it remains predominantly closed preventing efficient RNA loading. Our data reveal how the ligands of Prp43 regulate the structural dynamics of the RNA binding channel controlling the initial binding of RNA.

Regulation of the DEAH/RHA helicase Prp43 by the G-patch factor Pfa1

The DEAH/RHA helicase Prp43 remodels protein-RNA complexes during pre-messenger RNA (mRNA) splicing and ribosome biogenesis. The helicase activity and ATP turnover are intrinsically low and become activated by G-patch (gp) factors in the specific cellular context. The gp motif connects the helicase core to the flexible C-terminal domains, but it is unclear how this affects RecA domain movement during catalysis and the unwinding of RNA substrates. We developed single-molecule Förster Resonance Energy Transfer (smFRET) reporters to study RecA domain movements within Prp43 in real time. Without Pfa1(gp), the domains approach each other adopting predominantly a closed conformation. The addition of Pfa1(gp) induces an open state, which becomes even more prevalent during interaction with RNA. In the open state, Prp43 has reduced contacts with bound nucleotide and shows rapid adenosine diphosphate (ADP) release accelerating the transition from the weak (ADP) to the strong (apo) RNA binding state. Using smFRET labels on the RNA to probe substrate binding and unwinding, we demonstrate that Pfa1(gp) enables Prp43(ADP) to switch between RNA-bound and RNA-unbound states instead of dissociating from the RNA. ATP binding to the apo-enzyme induces the translocation along the RNA, generating the unwinding force required to melt proximal RNA structures. During ATP turnover, Pfa1(gp) stimulates alternating of the RecA domains between open and closed states. Consequently, the translocation becomes faster than dissociation from the substrate in the ADP state, allowing processive movement along the RNA. We provide a mechanistic model of DEAH/RHA helicase motility and reveal the principles of Prp43 regulation by G-patch proteins.

Defining the Functional Interactome of Spliceosome-Associated G-Patch Protein Gpl1 in the Fission Yeast Schizosaccharomyces pombe

Pre-mRNA splicing plays a fundamental role in securing protein diversity by generating multiple transcript isoforms from a single gene. Recently, it has been shown that specific G-patch domain-containing proteins are critical cofactors involved in the regulation of splicing processes. In this study, using the knock-out strategy, affinity purification and the yeast-two-hybrid assay, we demonstrated that the spliceosome-associated G-patch protein Gpl1 of the fission yeast S. pombe mediates interactions between putative RNA helicase Gih35 (SPAC20H4.09) and WD repeat protein Wdr83, and ensures their binding to the spliceosome. Furthermore, RT-qPCR analysis of the splicing efficiency of deletion mutants indicated that the absence of any of the components of the Gpl1-Gih35-Wdr83 complex leads to defective splicing of fet5 and pwi1, the reference genes whose unspliced isoforms harboring premature stop codons are targeted for degradation by the nonsense-mediated decay (NMD) pathway. Together, our results shed more light on the functional interactome of G-patch protein Gpl1 and revealed that the Gpl1-Gih35-Wdr83 complex plays an important role in the regulation of pre-mRNA splicing in S. pombe.

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.

A model for DHX15 mediated disassembly of A-complex spliceosomes

A critical step of pre-mRNA splicing is the recruitment of U2 snRNP to the branch point sequence of an intron. U2 snRNP conformation changes extensively during branch helix formation, and several RNA-dependent ATPases are implicated in the process. However, the molecular mechanisms involved remain to be fully dissected. We took advantage of the differential nucleotide triphosphates requirements for DExD/H-box enzymes to probe their contributions to in vitro spliceosome assembly. Both ATP and GTP hydrolysis support the formation of A-complex, indicating the activity of a DEAH-enzyme because DEAD-enzymes are selective for ATP. We immunodepleted DHX15 to assess its involvement, and although splicing efficiency decreases with reduced DHX15, A-complex accumulation incongruently increases. DHX15 depletion also results in the persistence of the atypical ATP-independent interaction between U2 snRNP and a minimal substrate that is otherwise destabilized in the presence of either ATP or GTP. These results lead us to hypothesize that DHX15 plays a quality control function in U2 snRNP's engagement with an intron. In efforts to identify the RNA target of DHX15, we determined that an extended polypyrimidine tract is not necessary for disruption of the atypical interaction between U2 snRNP and the minimal substrate. We also examined U2 snRNA by RNase H digestion and identified nucleotides in the branch binding region that become accessible with both ATP and GTP hydrolysis, again implicating a DEAH-enzyme. Together, our results demonstrate that multiple ATP-dependent rearrangements are likely involved in U2 snRNP addition to the spliceosome and that DHX15 may have an expanded role in maintaining splicing fidelity.

Regulation of DEAH-box RNA helicases by G-patch proteins

RNA helicases of the DEAH/RHA family form a large and conserved class of enzymes that remodel RNA protein complexes (RNPs) by translocating along the RNA. Driven by ATP hydrolysis, they exert force to dissociate hybridized RNAs, dislocate bound proteins or unwind secondary structure elements in RNAs. The sub-cellular localization of DEAH-helicases and their concomitant association with different pathways in RNA metabolism, such as pre-mRNA splicing or ribosome biogenesis, can be guided by cofactor proteins that specifically recruit and simultaneously activate them. Here we review the mode of action of a large class of DEAH-specific adaptor proteins of the G-patch family. Defined only by their eponymous short glycine-rich motif, which is sufficient for helicase binding and stimulation, this family encompasses an immensely varied array of domain compositions and is linked to an equally diverse set of functions. G-patch proteins are conserved throughout eukaryotes and are even encoded within retroviruses. They are involved in mRNA, rRNA and snoRNA maturation, telomere maintenance and the innate immune response. Only recently was the structural and mechanistic basis for their helicase enhancing activity determined. We summarize the molecular and functional details of G-patch-mediated helicase regulation in their associated pathways and their involvement in human diseases.

The G-patch activators Pfa1 and PINX1 exhibit different modes of interaction with the Prp43 RNA helicase

Prp43 is a DEAH-box RNA helicase involved in both splicing and ribosome biogenesis. Its activities are directly stimulated by several co-activators that share a G-patch domain. The substrates of Prp43, its mechanism of action and the modes of interaction with and activation by G-patch proteins have been only partially characterized. We investigated how Pfa1 and PINX1, two G-patch proteins involved in ribosome biogenesis, interact with Prp43. We demonstrate that a protruding loop connecting the β4 and β5 strands of Prp43 OB fold is crucial for the binding of the G-patch domain of Pfa1. However, neither this loop nor the entire OB fold of Prp43 is essential for PINX1 binding. We conclude that the binding modes of Pfa1 and PINX1 G-patches to Prp43 are different. Nevertheless, stimulation of the ATPase and helicase activities of Prp43 by both full-length Pfa1 and PINX1 requires the β4-β5 loop. Moreover, we show that disruption of this loop completely abrogates Prp43 activity during yeast ribosome biogenesis but does not prevent its integration within pre-ribosomal particles. We propose that the β4-β5 loop plays a crucial role in the transmission of conformational changes induced by binding of the G-patch to Prp43 active site and substrate RNA.

Structural basis for DEAH-helicase activation by G-patch proteins

RNA helicases exert mechanical force that changes RNA configurations in many essential cellular pathways, e.g., during mRNA maturation or assembly of ribosomes. DEAH helicases work by translocating along RNA and thereby unwind RNA duplexes or dissociate bound proteins. Because DEAH proteins are poor enzymes without intrinsic selectivity for target RNAs, they require adapter proteins that recruit them to functional sites and enhance their catalytic activity. One essential class of DEAH activators is formed by G-patch proteins, which bind helicases via their eponymous glycine-rich motif. We solved the structure of a G-patch bound to helicase DHX15. Our analysis suggests that G-patches tether mobile sections of DEAH helicases together and activate them by stabilizing a functional conformation with high RNA affinity.

RNA helicases of the DEAH/RHA family are involved in many essential cellular processes, such as splicing or ribosome biogenesis, where they remodel large RNA–protein complexes to facilitate transitions to the next intermediate. DEAH helicases couple adenosine triphosphate (ATP) hydrolysis to conformational changes of their catalytic core. This movement results in translocation along RNA, which is held in place by auxiliary C-terminal domains. The activity of DEAH proteins is strongly enhanced by the large and diverse class of G-patch activators. Despite their central roles in RNA metabolism, insight into the molecular basis of G-patch–mediated helicase activation is missing. Here, we have solved the structure of human helicase DHX15/Prp43, which has a dual role in splicing and ribosome assembly, in complex with the G-patch motif of the ribosome biogenesis factor NKRF. The G-patch motif binds in an extended conformation across the helicase surface. It tethers the catalytic core to the flexibly attached C-terminal domains, thereby fixing a conformation that is compatible with RNA binding. Structures in the presence or absence of adenosine diphosphate (ADP) suggest that motions of the catalytic core, which are required for ATP binding, are still permitted. Concomitantly, RNA affinity, helicase, and ATPase activity of DHX15 are increased when G-patch is bound. Mutations that detach one end of the tether but maintain overall binding severely impair this enhancement. Collectively, our data suggest that the G-patch motif acts like a flexible brace between dynamic portions of DHX15 that restricts excessive domain motions but maintains sufficient flexibility for catalysis.

Sgd1 is an MIF4G domain-containing cofactor of the RNA helicase Fal1 and associates with the 5' domain of the 18S rRNA sequence

Assembly of eukaryotic ribosomal subunits is a complex and dynamic process involving the action of more than 200 trans-acting assembly factors. Although recent cryo-electron microscopy structures have provided information on architecture of several pre-ribosomal particles and the binding sites of many AFs, the RNA and protein interactions of many other AFs not captured in these snapshots still remain elusive. RNA helicases are key regulators of structural rearrangements within pre-ribosomal complexes and here we have analysed the eIF4A-like RNA helicase Fal1 and its putative cofactor Sgd1. Our data show that these proteins interact directly via the MIF4G domain of Sgd1 and that the MIF4G domain of Sgd1 stimulates the catalytic activity of Fal1 in vitro. The catalytic activity of Fal1, and the interaction between Fal1 and Sgd1, are required for efficient pre-rRNA processing at the A₀, A₁ and A₂ sites. Furthermore, Sgd1 co-purifies the early small subunit biogenesis factors Lcp5 and Rok1, suggesting that the Fal1-Sgd1 complex likely functions within the SSU processome. In vivo crosslinking data reveal that Sgd1 binds to helix H12 of the 18S rRNA sequence and we further demonstrate that this interaction is formed by the C-terminal region of the protein, which is essential for its function in ribosome biogenesis.

The DEAH-box RNA helicase Dhr1 contains a remarkable carboxyl terminal domain essential for small ribosomal subunit biogenesis

Ribosome biogenesis is an essential process in all living cells, which entails countless highly sequential and dynamic structural reorganization events. These include formation of dozens RNA helices through Watson-Crick base-pairing within ribosomal RNAs (rRNAs) and between rRNAs and small nucleolar RNAs (snoRNAs), transient association of hundreds of proteinaceous assembly factors to nascent precursor (pre-)ribosomes, and stable assembly of ribosomal proteins. Unsurprisingly, the largest group of ribosome assembly factors are energy-consuming proteins (NTPases) including 25 RNA helicases in budding yeast. Among these, the DEAH-box Dhr1 is essential to displace the box C/D snoRNA U3 from the pre-rRNAs where it is bound in order to prevent premature formation of the central pseudoknot, a dramatic irreversible long-range interaction essential to the overall folding of the small ribosomal subunit. Here, we report the crystal structure of the Dhr1 helicase module, revealing the presence of a remarkable carboxyl-terminal domain essential for Dhr1 function in ribosome biogenesis in vivo and important for its interaction with its coactivator Utp14 in vitro. Furthermore, we report the functional consequences on ribosome biogenesis of DHX37 (human Dhr1) mutations found in patients suffering from microcephaly and other neurological diseases.

Identification of proteins associated with splicing factors Ntr1, Ntr2, Brr2 and Gpl1 in the fission yeast Schizosaccharomyces pombe

The spliceosome is a complex molecular machine assembled from many components, which catalyzes the removal of introns from mRNA precursors. Our previous study revealed that the Nrl1 (NRDE-2 like 1) protein associates with spliceosome proteins and regulates pre-mRNA splicing and homologous recombination-dependent R-loop formation in the fission yeast Schizosaccharomyces pombe. Here, we identify proteins associated with splicing factors Ntr1, Ntr2, Brr2 and Gpl1, a poorly characterized G-patch domain-containing protein required for efficient splicing. This work provides new evidence that Nrl1 and splicing factors physically interact and reveals additional insights into the protein interaction network of the spliceosome. We discuss implications of these findings in the light of recent progress in our understanding of how Nrl1 and splicing factors ensure genome stability.

Molecular mechanism of the RNA helicase DHX37 and its activation by UTP14A in ribosome biogenesis

Eukaryotic ribosome biogenesis is a highly orchestrated process involving numerous assembly factors including ATP-dependent RNA helicases. The DEAH helicase DHX37 (Dhr1 in yeast) is activated by the ribosome biogenesis factor UTP14A to facilitate maturation of the small ribosomal subunit. We report the crystal structure of DHX37 in complex with single-stranded RNA, revealing a canonical DEAH ATPase/helicase architecture complemented by a structurally unique carboxy-terminal domain (CTD). Structural comparisons of the nucleotide-free DHX37-RNA complex with DEAH helicases bound to RNA and ATP analogs reveal conformational changes resulting in a register shift in the bound RNA, suggesting a mechanism for ATP-dependent 3'-5' RNA translocation. We further show that a conserved sequence motif in UTP14A interacts with and activates DHX37 by stimulating its ATPase activity and enhancing RNA binding. In turn, the CTD of DHX37 is required, but not sufficient, for interaction with UTP14A in vitro and is essential for ribosome biogenesis in vivo. Together, these results shed light on the mechanism of DHX37 and the function of UTP14A in controlling its recruitment and activity during ribosome biogenesis.

MtDNA population variation in Myalgic encephalomyelitis/Chronic fatigue syndrome in two populations: a study of mildly deleterious variants

Myalgic Encephalomyelitis (ME), also known as Chronic Fatigue Syndrome (CFS) is a debilitating condition. There is growing interest in a possible etiologic or pathogenic role of mitochondrial dysfunction and mitochondrial DNA (mtDNA) variation in ME/CFS. Supporting such a link, fatigue is common and often severe in patients with mitochondrial disease. We investigate the role of mtDNA variation in ME/CFS. No proven pathogenic mtDNA mutations were found. We then investigated population variation. Two cohorts were analysed, one from the UK (n = 89 moderately affected; 29 severely affected) and the other from South Africa (n = 143 moderately affected). For both cohorts, ME/CFS patients had an excess of individuals without a mildly deleterious population variant. The differences in population variation might reflect a mechanism important to the pathophysiology of ME/CFS.

Human RNA cap1 methyltransferase CMTr1 cooperates with RNA helicase DHX15 to modify RNAs with highly structured 5' termini

The 5′-cap structure, characteristic for RNA polymerase II-transcribed RNAs, plays important roles in RNA metabolism. In humans, RNA cap formation includes post-transcriptional modification of the first transcribed nucleotide by RNA cap1 methyltransferase (CMTr1). Here, we report that CMTr1 activity is hindered towards RNA substrates with highly structured 5′ termini. We found that CMTr1 binds ATP-dependent RNA DHX15 helicase and that this interaction, mediated by the G-patch domain of CMTr1, has an advantageous effect on CMTr1 activity towards highly structured RNA substrates. The effect of DHX15 helicase activity is consistent with the strength of the secondary structure that has to be removed for CMTr1 to access the 5′-terminal residues in a single-stranded conformation. This is, to our knowledge, the first demonstration of the involvement of DHX15 in post-transcriptional RNA modification, and the first example of a molecular process in which DHX15 directly affects the activity of another enzyme. Our findings suggest a new mechanism underlying the regulatory role of DHX15 in the RNA capping process. RNAs with highly structured 5′ termini constitute a significant fraction of the human transcriptome. Hence, CMTr1–DHX15 cooperation is likely to be important for the metabolism of RNA polymerase II-transcribed RNAs.

This article is part of the theme issue ‘5′ and 3′ modifications controlling RNA degradation’.

Crystal Structure of the Escherichia coli DExH-Box NTPase HrpB

Eukaryotic DExH-box proteins are important post-transcriptional gene regulators, many of which employ RNA-stimulated nucleoside triphosphatase activity to remodel RNAs or ribonucleoprotein complexes. However, bacterial DExH-box proteins are structurally and functionally poorly characterized. We report the crystal structure of the Escherichia coli DExH-box protein HrpB. A globular head is composed of dual RecA, winged-helix, helical bundle and oligonucleotide/oligosaccharide-binding domains, resembling a compact version of eukaryotic DExH-box proteins. Additionally, HrpB harbors a C-terminal region not found in proteins with known structure, which bestows the protein with unique interaction potential. Interaction and activity assays showed that the protein binds RNA but not DNA, hydrolyzes all nucleoside triphosphates in an RNA-stimulated manner, but does not unwind diverse model RNAs in vitro. These observations can be rationalized by detailed comparisons with structurally characterized eukaryotic DExH-box proteins. Comparative phenotypic analyses of an E. coli hrpB knockout mutant suggested diverse functions of HrpB homologs in different bacteria.

Crystal structure of the spliceosomal DEAH-box ATPase Prp2

The DEAH-box ATPase Prp2 plays a key role in the activation of the spliceosome as it promotes the transition from the Bact to the catalytically active B* spliceosome. Here, four crystal structures of Prp2 are reported: one of the nucleotide-free state and three different structures of the ADP-bound state. The overall conformation of the helicase core, formed by two RecA-like domains, does not differ significantly between the ADP-bound and the nucleotide-free states. However, intrinsic flexibility of Prp2 is observed, varying the position of the C-terminal domains with respect to the RecA domains. Additionally, in one of the structures a unique ADP conformation is found which has not been observed in any other DEAH-box, DEAD-box or NS3/NPH-II helicase.

DHX15 regulates CMTR1-dependent gene expression and cell proliferation

DHX15 helicase regulates CMTR1-dependent first transcribed nucleotide ribose O-2 methylation.

CMTR1 contributes to mRNA cap formation by methylating the first transcribed nucleotide ribose at the O-2 position. mRNA cap O-2 methylation has roles in mRNA stabilisation and translation, and self-RNA tolerance in innate immunity. We report that CMTR1 is recruited to serine-5–phosphorylated RNA Pol II C-terminal domain, early in transcription. We isolated CMTR1 in a complex with DHX15, an RNA helicase functioning in splicing and ribosome biogenesis, and characterised it as a regulator of CMTR1. When DHX15 is bound, CMTR1 activity is repressed and the methyltransferase does not bind to RNA pol II. Conversely, CMTR1 activates DHX15 helicase activity, which is likely to impact several nuclear functions. In HCC1806 breast carcinoma cell line, the DHX15–CMTR1 interaction controls ribosome loading of a subset of mRNAs and regulates cell proliferation. The impact of the CMTR1–DHX15 interaction is complex and will depend on the relative expression of these enzymes and their interactors, and the cellular dependency on different RNA processing pathways.

Unravelling the Mechanisms of RNA Helicase Regulation

RNA helicases are critical regulators at the nexus of multiple pathways of RNA metabolism, and in the complex cellular environment, tight spatial and temporal regulation of their activity is essential. Dedicated protein cofactors play key roles in recruiting helicases to specific substrates and modulating their catalytic activity. Alongside individual RNA helicase cofactors, networks of cofactors containing evolutionarily conserved domains such as the G-patch and MIF4G domains highlight the potential for cross-regulation of different aspects of gene expression. Structural analyses of RNA helicase-cofactor complexes now provide insight into the diverse mechanisms by which cofactors can elicit specific and coordinated regulation of RNA helicase action. Furthermore, post-translational modifications (PTMs) and long non-coding RNA (lncRNA) regulators have recently emerged as novel modes of RNA helicase regulation.

Studying structure and function of spliceosomal helicases

The splicing of eukaryotic precursor mRNAs requires the activity of at least three DEAD-box helicases, one Ski2-like helicase and four DEAH-box helicases. High resolution structures for five of these spliceosomal helicases were obtained by means of X-ray crystallography. Additional low resolution structural information could be derived from single particle cryo electron microscopy and small angle X-ray scattering. The functional characterization includes biochemical methods to measure the ATPase and helicase activities. This review gives an overview on the techniques used to gain insights in to the structure and function of spliceosomal helicases.