A Synthetic Biology Approach Identifies the Mammalian UPR RNA Ligase RtcB

Lu, Yao; Liang, Feng; Wang, Xiaozhong

doi:10.1016/j.molcel.2014.06.032

Cited by 208 publications

(185 citation statements)

References 53 publications

(95 reference statements)

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“…Likewise, RtcB is required for tRNA splicing in humans (Popow et al 2011). Moreover, RtcB activity is also required for XBP1 splicing during the unfolded protein response in metazoa Kosmaczewski et al 2014;Lu et al 2014). Attesting to the importance of Archease activating RtcB in mammals, a decrease in the concentration of Archease has been shown to impair both tRNA splicing and XBP1 splicing Popow et al 2014).…”

Section: Discussionmentioning

confidence: 99%

“…RtcB is an essential enzyme for the ligation of tRNAs in metazoa (Popow et al 2011), and possibly archaea Sarmiento et al 2013), upon intron removal by the tRNA splicing endonuclease (Abelson et al 1998;Popow et al 2012). RtcB is also essential for the ligation of XBP1 exons in metazoa upon intron removal by IRE1, which initiates the unfolded protein response during endoplasmic reticulum stress Kosmaczewski et al 2014;Lu et al 2014). RtcB-catalyzed RNA ligation proceeds through three nucleotidyl transfer steps, with 2 ′ ,3 ′ -cyclic phosphate termini being hydrolyzed to 3 ′ -p termini in a step that precedes 3 ′ -p activation with GMP Chakravarty and Shuman 2012;Chakravarty et al 2012).…”

Section: Introductionmentioning

confidence: 99%

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Coevolution of RtcB and Archease created a multiple-turnover RNA ligase

Desai

Beltrame

Raines

2015

RNA

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RtcB is a noncanonical RNA ligase that joins either 2 ′ ,3 ′ -cyclic phosphate or 3 ′ -phosphate termini to 5 ′ -hydroxyl termini. The genes encoding RtcB and Archease constitute a tRNA splicing operon in many organisms. Archease is a cofactor of RtcB that accelerates RNA ligation and alters the NTP specificity of the ligase from Pyrococcus horikoshii. Yet, not all organisms that encode RtcB also encode Archease. Here we sought to understand the differences between Archease-dependent and Archease-independent RtcBs so as to illuminate the evolution of Archease and its function. We report on the Archeasedependent RtcB from Thermus thermophilus and the Archease-independent RtcB from Thermobifida fusca. We find that RtcB from T. thermophilus can catalyze multiple turnovers only in the presence of Archease. Remarkably, Archease from P. horikoshii can activate T. thermophilus RtcB, despite low sequence identity between the Archeases from these two organisms. In contrast, RtcB from T. fusca is a single-turnover enzyme that is unable to be converted into a multiple-turnover ligase by Archease from either P. horikoshii or T. thermophilus. Thus, our data indicate that Archease likely evolved to support multiple-turnover activity of RtcB and that coevolution of the two proteins is necessary for a functional interaction.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Coevolution of RtcB and Archease created a multiple-turnover RNA ligase

Desai

Beltrame

Raines

2015

RNA

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“…In yeast cells (Saccharomyces cerevisiae), activated Ire1p cleaves the unspliced HAC1 mRNA at two RNA stem-loops to excise an intervening 252-base intron, and then the tRNA ligase Trl1p joins the two exons followed by removal of the junctional 2 ′ phosphate in the second step by 2 ′ phosphotransferase Tpt1p, generating the spliced form of HAC1 mRNA (Sidrauski et al 1996;Sidrauski and Walter 1997;Schwer et al 2004). Similarly, in metazoans, IRE1α first removes a 23-nt (Caenorhabditis elegans and Drosophila melanogaster) or 26-nt (mammals) intron from the unspliced XBP1 mRNA (Tirasophon et al 1998;Shen et al 2001;Yoshida et al 2001;Calfon et al 2002), and the proximally located tRNA ligase RTCB joins the two cleaved XBP1 exons to generate a mature mRNA to produce the spliced form of XBP1 (Kosmaczewski et al 2014;Lu et al 2014). XBP1 mRNA appears to be the only substrate for IRE1α for splicing, as sophisticated searches for other substrates have failed (Bai et al 2014).…”

Section: Eif2α Kinasesmentioning

confidence: 99%

Physiological/pathological ramifications of transcription factors in the unfolded protein response

2017

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Numerous environmental, physiological, and pathological insults disrupt protein-folding homeostasis in the endoplasmic reticulum (ER), referred to as ER stress. Eukaryotic cells evolved a set of intracellular signaling pathways, collectively termed the unfolded protein response (UPR), to maintain a productive ER protein-folding environment through reprogramming gene transcription and mRNA translation. The UPR is largely dependent on transcription factors (TFs) that modulate expression of genes involved in many physiological and pathological conditions, including development, metabolism, inflammation, neurodegenerative diseases, and cancer. Here we summarize the current knowledge about these mechanisms, their impact on physiological/pathological processes, and potential therapeutic applications.

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“…Activated IRE1α cleaves two specific sites of the precursor form of XBP1 (XBP1u) mRNA (14, 15). The recently identified RtcB joins the 5′ and 3′ fragments, which results in the removal of the 26-base fragment in the middle of the open-reading frame (16)(17)(18)(19). This splicing reaction creates a translational frame shift.…”

mentioning

confidence: 99%

Autonomous translational pausing is required for XBP1u mRNA recruitment to the ER via the SRP pathway

Kanda

Yanagitani

Yokota

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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Unconventional mRNA splicing on the endoplasmic reticulum (ER) membrane is the sole conserved mechanism in eukaryotes to transmit information regarding misfolded protein accumulation to the nucleus to activate the stress response. In metazoans, the unspliced form of X-box-binding protein 1 (XBP1u) mRNA is recruited to membranes as a ribosome nascent chain (RNC) complex for efficient splicing. We previously reported that both hydrophobic (HR2) and translational pausing regions of XBP1u are important for the recruitment of its own mRNA to membranes. However, its precise location and the molecular mechanism of translocation are unclear. We show that XBP1u-RNC is specifically recruited to the ER membrane in an HR2-and translational pausing-dependent manner by immunostaining, fluorescent recovery after photobleaching, and biochemical analyses. Notably, translational pausing during XBP1u synthesis is indispensable for the recognition of HR2 by the signal recognition particle (SRP), resulting in efficient ER-specific targeting of the complex, similar to secretory protein targeting to the ER. On the ER, the XBP1u nascent chain is transferred from the SRP to the translocon; however, it cannot pass through the translocon or insert into the membrane. Therefore, our results support a noncanonical mechanism by which mRNA substrates are recruited to the ER for unconventional splicing. and subsequent protein folding are associated with a number of diseases. Accordingly, a detailed understanding of the mechanisms that mediate these complex processes is necessary. In eukaryotes, secretory proteins are initially translated by cytosolic ribosomes. When the N-terminal signal peptide reaches outside of the peptide exit channel in the ribosome, the ribosome nascent chain (RNC) complex is recognized by the signal recognition particle (SRP) and peptide elongation is slowed (1-5). This SRP-RNC complex is then recruited to the ER via the affinity between SRP and SRP receptor (SR) that exists in the ER membrane (2, 3). The RNC complex is then delivered to the polypeptide channel in the ER (i.e., the Sec61 translocon) (6). SRP is released from the RNC, which cancels the slowed-down elongation. As a result, the ER-targeted ribosome cotranslationally translocates its synthesizing polypeptide into the luminal space of the ER. The translocated protein is folded into its native 3D structure with the help of molecular chaperones and folding enzymes (7). The folded proteins are sorted to their final destinations to exert their functions.The burden of new proteins entering the ER varies widely among conditions, such as cell differentiation, environmental conditions, and the physiological state of the cell (8, 9). In addition, the folding capacity in the ER is easily compromised by many stressful conditions, including glucose starvation, virus infection, and perturbations in the Ca 2+ concentration. Therefore, it is necessary for cells to manage the imbalance between the load of newly entering proteins and the folding capacity in the ER, and this i...

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A Synthetic Biology Approach Identifies the Mammalian UPR RNA Ligase RtcB

Cited by 208 publications

References 53 publications

Coevolution of RtcB and Archease created a multiple-turnover RNA ligase

Coevolution of RtcB and Archease created a multiple-turnover RNA ligase

Physiological/pathological ramifications of transcription factors in the unfolded protein response

Autonomous translational pausing is required for XBP1u mRNA recruitment to the ER via the SRP pathway

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