Novel regulatory principles of the spliceosomal Brr2 RNA helicase and links to retinal disease in humans

Mozaffari‐Jovin, Sina; Wandersleben, Traudy; Santos, K.F.; Will, Cindy L.; Lührmann, Reinhard; Wahl, Markus C.

doi:10.4161/rna.28353

Cited by 42 publications

(55 citation statements)

References 72 publications

(126 reference statements)

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“…Fine-tuning of the binding strength of the Jab1 C-terminal tail to the Brr2 RNAbinding tunnel likely relies on the intrinsically unstructured nature of this tail. 88 Taken together, presently available structures of isolated Brr2-Jab1 complexes, tri-snRNPs and spliceosomes in combination with functional studies support the notion that the NTR is essential to shut off Brr2 activity during tri-snRNP assembly and during several stages of splicing, and that the Jab1 domain remains stably bound to Brr2 during all phases of splicing, in which Brr2 is present (Fig. 1).…”

Section: Brr2 Regulation During Splicingsupporting

confidence: 63%

“…53,56 The functional relevance of this mode of Brr2 inhibition is underscored by the observation that mutations in Prp8, which affect residues in the Jab1 C-terminal tail and interfere with its function, lead to a severe form of retinitis pigmentosa in human. 53,88 The tail insertion was first observed in the structure of a human Brr2-Jab1 complex, 53 in which the Brr2 subunit lacked all elements of the NTR except the NC-clamp, but was not seen in a slightly further truncated yeast Brr2-Jab1 complex. 38 These findings raised the question whether the Jab1 tail insertion is conserved among organisms.…”

Section: Brr2 Regulation Via Trans-acting Factorsmentioning

confidence: 98%

“…53,88 Likewise, Jab1 bearing an intact tail can enhance Brr2 activity and efficiency in vitro after displacement of the tail by larger amounts of substrate RNA. 53,88 Recent studies suggested that Jab1-mediated stimulation of Brr2 might be required at the stage of spliceosome catalytic activation, during which Brr2 needs to unwind U4/U6 di-snRNA decorated with U4/U6 proteins; addition of the U4/U6 di-snRNP proteins Snu13, Prp31 and Prp3 led to a stepwise decrease in unwinding activity, which could be efficiently restored upon addition of Jab1 DC . 29 On the molecular level, Jab1-mediated Brr2 activation may in part be due to bridging of the N-terminal HB and RecA2 domains by the proximal portion of the Jab1 tail (Fig.…”

Section: Brr2 Regulation Via Trans-acting Factorsmentioning

confidence: 99%

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Functions and regulation of the Brr2 RNA helicase during splicing

2016

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Pre-mRNA splicing entails the stepwise assembly of an inactive spliceosome, its catalytic activation, splicing catalysis and spliceosome disassembly. Transitions in this reaction cycle are accompanied by compositional and conformational rearrangements of the underlying RNA-protein interaction networks, which are driven and controlled by 8 conserved superfamily 2 RNA helicases. The Ski2-like helicase, Brr2, provides the key remodeling activity during spliceosome activation and is additionally implicated in the catalytic and disassembly phases of splicing, indicating that Brr2 needs to be tightly regulated during splicing. Recent structural and functional analyses have begun to unravel how Brr2 regulation is established via multiple layers of intra-and inter-molecular mechanisms. Brr2 has an unusual structure, including a long N-terminal region and a catalytically inactive C-terminal helicase cassette, which can auto-inhibit and auto-activate the enzyme, respectively. Both elements are essential, also serve as protein-protein interaction devices and the N-terminal region is required for stable Brr2 association with the tri-snRNP, tri-snRNP stability and retention of U5 and U6 snRNAs during spliceosome activation in vivo. Furthermore, a C-terminal region of the Prp8 protein, comprising consecutive RNase H-like and Jab1/MPN-like domains, can both up-and downregulate Brr2 activity. Biochemical studies revealed an intricate cross-talk among the various cis-and transregulatory mechanisms. Comparison of isolated Brr2 to electron cryo-microscopic structures of yeast and human U4/U6 U5 tri-snRNPs and spliceosomes indicates how some of the regulatory elements exert their functions during splicing. The various modulatory mechanisms acting on Brr2 might be exploited to enhance splicing fidelity and to regulate alternative splicing. KEYWORDSPre-mRNA splicing; regulation of pre-mRNA splicing; remodeling of RNAprotein complexes; RNA helicase structure, function and regulation; spliceosome catalytic activation

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Section: Brr2 Regulation During Splicingsupporting

confidence: 63%

Section: Brr2 Regulation Via Trans-acting Factorsmentioning

confidence: 98%

Section: Brr2 Regulation Via Trans-acting Factorsmentioning

confidence: 99%

See 1 more Smart Citation

Functions and regulation of the Brr2 RNA helicase during splicing

2016

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“…This is an interesting result, as Brr2 is expected to unwind U4/U6 in the context of the trisnRNP (Laggerbauer et al 1998;Raghunathan and Guthrie 1998), dissociating it into three individual snRNPs (free U4, U5, and U6), and suggests that more is required to activate Brr2 to unwind U4/U6. Thus, it is likely that, though the binding affinity between Brr2 and the Prp8 Jab1/MPN domain is high (Mozaffari-Jovin et al 2014), the Prp8 Jab1/MPN tail can dissociate from the Brr2 RNA binding pocket upon minute conformational changes. This is consistent with a previous Brr2 Prp8 Jab1/MPN domain co-crystal (Nguyen et al 2013), where the density corresponding to the Prp8 Jab1/MPN tail is absent.…”

Section: Characterization Of a Prp8-rp Splicing Defectmentioning

confidence: 99%

“…Later biochemical studies revealed that the Prp8 Jab1/MPN domain also stimulates Brr2 helicase activity while suppressing Brr2 ATPase activity (Pena et al 2007;Maeder et al 2009;Mozaffari-Jovin et al 2014). Further studies have revealed additional complexity.…”

Section: Introductionmentioning

confidence: 99%

Prp8 retinitis pigmentosa mutants cause defects in the transition between the catalytic steps of splicing

Mayerle

Guthrie

2016

RNA

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Pre-mRNA splicing must occur with high fidelity and efficiency for proper gene expression. The spliceosome uses DExD/H box helicases to promote on-pathway interactions while simultaneously minimizing errors. Prp8 and Snu114, an EF2-like GTPase, regulate the activity of the Brr2 helicase, promoting RNA unwinding by Brr2 at appropriate points in the splicing cycle and repressing it at others. Mutations linked to retinitis pigmentosa (RP), a disease that causes blindness in humans, map to the Brr2 regulatory region of Prp8. Previous in vitro studies of homologous mutations in Saccharomyces cerevisiae show that Prp8-RP mutants cause defects in spliceosome activation. Here we show that a subset of RP mutations in Prp8 also causes defects in the transition between the first and second catalytic steps of splicing. Though Prp8-RP mutants do not cause defects in splicing fidelity, they result in an overall decrease in splicing efficiency. Furthermore, genetic analyses link Snu114 GTP/GDP occupancy to Prp8-dependent regulation of Brr2. Our results implicate the transition between the first and second catalytic steps as a critical place in the splicing cycle where Prp8-RP mutants influence splicing efficiency. The location of the Prp8-RP mutants, at the "hinge" that links the Prp8 Jab1-MPN regulatory "tail" to the globular portion of the domain, suggests that these Prp8-RP mutants inhibit regulated movement of the Prp8 Jab1/MPN domain into the Brr2 RNA binding channel to transiently inhibit Brr2. Therefore, in Prp8-linked RP, disease likely results not only from defects in spliceosome assembly and activation, but also because of defects in splicing catalysis.

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Cajal body function in genome organization and transcriptome diversity

et al. 2016

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Nuclear bodies contribute to nonrandom organization of the human genome and nuclear function. Using a major prototypical nuclear body, the Cajal body, as an example, we suggest that these structures assemble at specific gene loci located across the genome as a result of high transcriptional activity. Subsequently, target genes are physically clustered in close proximity in Cajal body-containing cells. However, Cajal bodies are observed in only a limited number of human cell types, including neuronal and cancer cells. Ultimately, Cajal body depletion perturbs splicing kinetics by reducing target small nuclear RNA (snRNA) transcription and limiting the levels of spliceosomal snRNPs, including their modification and turnover following each round of RNA splicing. As such, Cajal bodies are capable of shaping the chromatin interaction landscape and the transcriptome by influencing spliceosome kinetics. Future studies should concentrate on characterizing the direct influence of Cajal bodies upon small nuclear RNA gene transcriptional dynamics.

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Novel regulatory principles of the spliceosomal Brr2 RNA helicase and links to retinal disease in humans

Cited by 42 publications

References 72 publications

Functions and regulation of the Brr2 RNA helicase during splicing

Functions and regulation of the Brr2 RNA helicase during splicing

Prp8 retinitis pigmentosa mutants cause defects in the transition between the catalytic steps of splicing

Cajal body function in genome organization and transcriptome diversity

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