Delta-secretase (AEP) mediates tau-splicing imbalance and accelerates cognitive decline in tauopathies

SRPK2 is abnormally activated in tauopathies including Alzheimer’s disease (AD). SRPK2 is known to play an important role in pre–mRNA splicing by phosphorylating SR-splicing factors. Dysregulation of tau exon 10 pre–mRNA splicing causes pathological imbalances in 3R- and 4R-tau, leading to neurodegeneration; however, the role of SRPK2 in these processes remains unclear. Here we show that delta-secretase (also known as asparagine endopeptidase; AEP), which is activated in AD, cleaves SRPK2 and increases its nuclear translocation as well as kinase activity, augmenting exon 10 inclusion. Conversely, AEP-uncleavable SRPK2 N342A mutant increases exon 10 exclusion. Lentiviral expression of truncated SRPK2 increases 4R-tau isoforms and accelerates cognitive decline in htau mice. Uncleavable SRPK2 N342A expression improves synaptic functions and prevents spatial memory deficits in tau intronic mutant FTDP-17 transgenic mice. Hence, AEP mediates tau-splicing imbalance in tauopathies via cleaving SRPK2.

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Regulation of neuronal mRNA splicing and Tau isoform ratio by ATXN3 through deubiquitylation of splicing factors

10.1101/711424 ◽

2019 ◽

Author(s):

Andreia Neves-Carvalho ◽

Sara Duarte-Silva ◽

Joana Silva ◽

Bruno Almeida ◽

Sasja Heetveld ◽

...

Keyword(s):

Neurodegenerative Disorders ◽

Rna Metabolism ◽

Mrna Splicing ◽

Splicing Factors ◽

Loss Of Function ◽

Relevant Role ◽

The Brain ◽

Precise Role ◽

Exon 10

ABSTRACTThe ubiquitylation/deubiquitylation balance in cells is maintained by Deubiquitylating enzymes, including ATXN3. The precise role of this protein, mutated in SCA3, remains elusive, as few substrates for its deubiquitylating activity were identified. Therefore, we characterized the ubiquitome of neuronal cells lacking ATXN3, and found altered polyubiquitylation in a large proportion of proteins involved in RNA metabolism, including splicing factors. Using transcriptomic analysis and reporter minigenes we confirmed that splicing was globally altered in these cells. Among the targets with altered splicing was SRSF7 (9G8), a key regulator of MAPT (Tau) exon 10 splicing. Loss-of-function of ATXN3 led to a deregulation of MAPT exon 10 splicing resulting in a decreased 4R/3R-Tau ratio. Similar alterations were found in the brain of a SCA3 mouse and humans, pointing to a relevant role of this mechanism in SCA3, and establishing a previously unsuspected link between two key proteins involved in different neurodegenerative disorders.

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Nuclear ErbB2 represses DEPTOR transcription to inhibit autophagy in breast cancer cells

Cell Death and Disease ◽

10.1038/s41419-021-03686-9 ◽

2021 ◽

Vol 12 (4) ◽

Author(s):

Yanli Bi ◽

Longyuan Gong ◽

Pengyuan Liu ◽

Xiufang Xiong ◽

Yongchao Zhao

Keyword(s):

Breast Cancer ◽

Cancer Cells ◽

Transcriptional Repression ◽

Breast Cancer Cells ◽

Kinase Activity ◽

Nuclear Translocation ◽

Extracellular Signals ◽

Consensus Binding Sequence ◽

Binding Sequence

AbstractErbB2, a classical receptor tyrosine kinase, is frequently overexpressed in breast cancer cells. Although the role of ErbB2 in the transmission of extracellular signals to intracellular matrix has been widely studied, the functions of nuclear ErbB2 remain largely elusive. Here, we report a novel function of nuclear ErbB2 in repressing the transcription of DEPTOR, a direct inhibitor of mTOR. Nuclear ErbB2 directly binds to the consensus binding sequence in the DEPTOR promoter to repress its transcription. The kinase activity of ErbB2 is required for its nuclear translocation and transcriptional repression of DEPTOR. Moreover, the repressed DEPTOR by nuclear ErbB2 inhibits the induction of autophagy by activating mTORC1. Thus, our study reveals a novel mechanism for autophagy regulation by functional ErbB2, which translocates to the nucleus and acts as a transcriptional regulator to suppress DEPTOR transcription, leading to activation of the PI3K/AKT/mTOR pathway to inhibit autophagy.

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Human Cancer-Associated Mutations of SF3B1 Lead to a Splicing Modification of Its Own RNA

Cancers ◽

10.3390/cancers12030652 ◽

2020 ◽

Vol 12 (3) ◽

pp. 652

Author(s):

Tiffany Bergot ◽

Eric Lippert ◽

Nathalie Douet-Guilbert ◽

Séverine Commet ◽

Laurent Corcos ◽

...

Keyword(s):

Amino Acids ◽

Human Cancer ◽

Myeloid Cell ◽

Mrna Splicing ◽

Splicing Factors ◽

Small Nuclear Ribonucleoprotein ◽

Genes Encoding ◽

Protein Isoform ◽

Nuclear Ribonucleoprotein

Deregulation of pre-mRNA splicing is observed in many cancers and hematological malignancies. Genes encoding splicing factors are frequently mutated in myelodysplastic syndromes, in which SF3B1 mutations are the most frequent. SF3B1 is an essential component of the U2 small nuclear ribonucleoprotein particle that interacts with branch point sequences close to the 3’ splice site during pre-mRNA splicing. SF3B1 mutations mostly lead to substitutions at restricted sites in the highly conserved HEAT domain, causing a modification of its function. We found that SF3B1 was aberrantly spliced in various neoplasms carrying an SF3B1 mutation, by exploring publicly available RNA sequencing raw data. We aimed to characterize this novel SF3B1 transcript, which is expected to encode a protein with an insertion of eight amino acids in the H3 repeat of the HEAT domain. We investigated the splicing proficiency of this SF3B1 protein isoform, in association with the most frequent mutation (K700E), through functional complementation assays in two myeloid cell lines stably expressing distinct SF3B1 variants. The yeast Schizosaccharomyces pombe was also used as an alternative model. Insertion of these eight amino acids in wild-type or mutant SF3B1 (K700E) abolished SF3B1 essential function, highlighting the crucial role of the H3 repeat in the splicing function of SF3B1.

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Tau accumulation activates STAT1 triggering memory deficits via suppressing NMDA receptor expression

10.1101/437814 ◽

2018 ◽

Author(s):

Xiao-Guang Li ◽

Xiao-Yue Hong ◽

Ya-li Wang ◽

Shu-Juan Zhang ◽

Jun-Fei Zhang ◽

...

Keyword(s):

Nmda Receptor ◽

Nuclear Translocation ◽

Memory Performance ◽

Memory Deficits ◽

Dominant Negative ◽

Receptor Expression ◽

Signal Transducer ◽

Synaptic Functions ◽

Direct Binding ◽

The Brain

ABSTRACTIntracellular tau accumulation forming neurofibrillary tangles is hallmark pathology of Alzheimer's disease (AD), but how tau accumulation induces synapse impairment is elusive. By overexpressing human full-length wildtype tau (termed hTau) to mimic tau abnormality as seen in the brain of sporadic AD patients, we found that hTau accumulation activated JAK2 to phosphorylate STAT1 (Signal Transducer and Activator of Transcription 1) at Tyr701 leading to STAT1 dimerization, nuclear translocation and its activation. STAT1 activation suppressed expression of N-methyl-D-aspartate receptors (NMDARs) through direct binding to the specific GAS element of GluN1, GluN2A and GluN2B promoters, while knockdown STAT1 by AAV-Cre in STAT1flox/flox mice or expressing dominant negative Y701F-STAT1 efficiently rescued hTau-induced suppression of NMDARs expression with amelioration of synaptic functions and memory performance. These findings indicate that hTau accumulation impairs synaptic plasticity through JAK2/STAT1-induced suppression of NMDARs expression, revealing a novel mechanism for hTau-associated synapse and memory deficits.

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Potential therapeutic strategies for targeting Y-box-binding protein 1 in cancers

Current Cancer Drug Targets ◽

10.2174/1568009621666210831125001 ◽

2021 ◽

Vol 21 ◽

Author(s):

Jia-Wei Yang ◽

Chao Sun ◽

Qiu-Yang Jin ◽

Xing-Hui Qiao ◽

Xiu-Li Guo

Keyword(s):

Nuclear Translocation ◽

Binding Protein ◽

Circular Rna ◽

Therapeutic Strategies ◽

Mrna Splicing ◽

Tumor Proliferation ◽

Normal Cells ◽

The Past ◽

Potential Cancer

: As one of the most conservative proteins in evolution, Y-box-binding protein 1 (YB-1) has long been considered as a potential cancer target. YB-1 is usually poorly expressed in normal cells and exerts cellular physiological functions such as DNA repair, pre-mRNA splicing and mRNA stabilizing. In cancer cells, the expression of YB-1 is up-regulated and undergoes nuclear translocation and contributes to tumorigenesis, angiogenesis, tumor proliferation, invasion, migration and chemotherapy drug resistance. During the past decades, a variety of pharmacological tools such as siRNA, shRNA, microRNA, circular RNA, lncRNA and various compounds have been developed to target YB-1 for cancer therapy. In this review, we describe the physiological characteristics of YB-1 in detail, highlight the role of YB-1 in tumors and summarize the current therapeutic methods for targeting YB-1 in cancer.

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The WW Domain-Containing Proteins Interact with the Early Spliceosome and Participate in Pre-mRNA Splicing In Vivo

Molecular and Cellular Biology ◽

10.1128/mcb.24.20.9176-9185.2004 ◽

2004 ◽

Vol 24 (20) ◽

pp. 9176-9185 ◽

Cited By ~ 60

Author(s):

Kai-Ti Lin ◽

Ruei-Min Lu ◽

Woan-Yuh Tarn

Keyword(s):

Rna Polymerase Ii ◽

Nuclear Extract ◽

Mrna Splicing ◽

Splicing Factors ◽

Ww Domain ◽

Ww Domains ◽

Small Nuclear Ribonucleoprotein

ABSTRACT A growing body of evidence supports the coordination of mRNA synthesis and its subsequent processing events. Nuclear proteins harboring both WW and FF protein interaction modules bind to splicing factors as well as RNA polymerase II and may serve to link transcription with splicing. To understand how WW domains coordinate the assembly of splicing complexes, we used glutathione S-transferase fusions containing WW domains from CA150 or FBP11 in pull-down experiments with HeLa cell nuclear extract. The WW domains associate preferentially with the U2 small nuclear ribonucleoprotein and with splicing factors SF1, U2AF, and components of the SF3 complex. Accordingly, WW domain-associating factors bind to the 3′ part of a pre-mRNA to form a pre-spliceosome-like complex. We performed both in vitro and in vivo splicing assays to explore the role of WW/FF domain-containing proteins in this process. However, although CA150 is associated with the spliceosome, it appears to be dispensable for splicing in vitro. Nevertheless, in vivo depletion of CA150 substantially reduced splicing efficiency of a reporter pre-mRNA. Moreover, overexpression of CA150 fragments containing both WW and FF domains activated splicing and modulated alternative exon selection, probably by facilitating 3′ splice site recognition. Our results suggest an essential role of WW/FF domain-containing factors in pre-mRNA splicing that likely occurs in concert with transcription in vivo.

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Sip1, a Novel RS Domain-Containing Protein Essential for Pre-mRNA Splicing

Molecular and Cellular Biology ◽

10.1128/mcb.18.2.676 ◽

1998 ◽

Vol 18 (2) ◽

pp. 676-684 ◽

Cited By ~ 11

Author(s):

Wan-Jiang Zhang ◽

Jane Y. Wu

Keyword(s):

Protein Interactions ◽

Rna Binding ◽

Sequence Similarity ◽

Functional Characterization ◽

Nuclear Extract ◽

Mrna Splicing ◽

Splicing Factor ◽

Splicing Factors ◽

Interacting Protein

ABSTRACT Previous studies have shown that protein-protein interactions among splicing factors may play an important role in pre-mRNA splicing. We report here identification and functional characterization of a new splicing factor, Sip1 (SC35-interacting protein 1). Sip1 was initially identified by virtue of its interaction with SC35, a splicing factor of the SR family. Sip1 interacts with not only several SR proteins but also with U1-70K and U2AF65, proteins associated with 5′ and 3′ splice sites, respectively. The predicted Sip1 sequence contains an arginine-serine-rich (RS) domain but does not have any known RNA-binding motifs, indicating that it is not a member of the SR family. Sip1 also contains a region with weak sequence similarity to the Drosophila splicing regulator suppressor of white apricot (SWAP). An essential role for Sip1 in pre-mRNA splicing was suggested by the observation that anti-Sip1 antibodies depleted splicing activity from HeLa nuclear extract. Purified recombinant Sip1 protein, but not other RS domain-containing proteins such as SC35, ASF/SF2, and U2AF65, restored the splicing activity of the Sip1-immunodepleted extract. Addition of U2AF65 protein further enhanced the splicing reconstitution by the Sip1 protein. Deficiency in the formation of both A and B splicing complexes in the Sip1-depleted nuclear extract indicates an important role of Sip1 in spliceosome assembly. Together, these results demonstrate that Sip1 is a novel RS domain-containing protein required for pre-mRNA splicing and that the functional role of Sip1 in splicing is distinct from those of known RS domain-containing splicing factors.

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An ATM/CHK2 Signaling Pathway Induces Nuclear Translocation of SRPK2 in Cisplatin-Treated HeLa Cells

Processes ◽

10.3390/pr9122223 ◽

2021 ◽

Vol 9 (12) ◽

pp. 2223

Author(s):

Ioanna Sigala ◽

Anastasia Koukiali ◽

Androulla Miliotou ◽

Phaedra Lougiaki ◽

Thomas Giannakouros ◽

...

Keyword(s):

Dna Damage ◽

Hela Cells ◽

Cellular Response ◽

Kinase Activity ◽

Nuclear Translocation ◽

Decisive Role ◽

Chemotherapeutic Agents ◽

Nuclear Accumulation ◽

Drug Responsiveness

Chemotherapeutic agents are frequently used to treat various cancers, but the mechanisms mediating the cellular response to the drugs are still not fully understood. We previously reported that the nuclear translocation of serine/arginine protein kinases (SRPKs), triggered by the exposure of cells to DNA damage-inducers, plays a pivotal role in drug responsiveness. Here, we investigated the mechanism linking the nuclear accumulation of SRPK2 to the cisplatin treatment of HeLa cells. We present experimental evidence that nuclear SRPK2 acts downstream of Chk2 in the ATM/Chk2 cascade. The inhibition of ATM or Chk2 kinase activity by specific low-molecular-weight inhibitors restricted SRPK2 to the cytoplasm and conferred tolerance to cisplatin treatment. A similar effect was achieved by treating cells with SRPIN340, a selective SRPK1/2 inhibitor, thus confirming previous findings that kinase activity is indispensable for the nuclear import of SRPKs. These data add to previous findings that support a decisive role of SRPKs in coordinating cellular response to DNA damage.

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Dysregulated coordination of MAPT exon 2 and exon 10 splicing underlies different tau pathologies in PSP and AD

10.1101/2021.09.23.461598 ◽

2021 ◽

Author(s):

Kathryn R. Bowles ◽

Derian A. Pugh ◽

Laura-Maria Oja ◽

Benjamin M. Jadow ◽

Kurt Farrell ◽

...

Keyword(s):

Temporal Cortex ◽

Mrna Splicing ◽

Human Brain Tissue ◽

Gene Encoding ◽

Exon 2 ◽

Combinatorial Regulation ◽

Splicing Regulators ◽

Microtubule Binding Domain ◽

Exon 10

ABSTRACTUnderstanding regulation of MAPT splicing is important to the etiology of many nerurodegenerative diseases, including Alzheimer disease (AD) and progressive supranuclear palsy (PSP), in which different tau isoforms accumulate in pathologic inclusions. MAPT, the gene encoding the tau protein, undergoes complex alternative pre-mRNA splicing to generate six isoforms. Tauopathies can be categorized by the presence of tau aggregates containing either 3 (3R) or 4 (4R) microtubule binding domain repeats (determined by inclusion/exclusion of exon 10), but the role of the N terminal domain of the protein, determined by inclusion/exclusion of exons 2 and 3 has been less well studied. Using an unbiased correlational screen in human brain tissue, we observed coordination of MAPT exons 2 and 10 splicing. Expression of exon 2 splicing regulators and subsequently exon 2 inclusion are differentially disrupted in PSP and AD brain, resulting in the accumulation of 1N4R isoforms in PSP and 0N isoforms in AD temporal cortex. Furthermore, we identified different N-terminal isoforms of tau present in neurofibrillary tangles, dystrophic neurites and tufted astrocytes, indicating a role for differential N-terminal splicing in the development of disparate tau neuropathologies. We conclude that N-terminal splicing and combinatorial regulation with exon 10 inclusion/exclusion is likely to be important to our understanding of tauopathies.

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A termination-independent role of Rat1 in cotranscriptional splicing

10.1101/2020.07.23.218495 ◽

2020 ◽

Author(s):

Zuzer Dhoondia ◽

Hesham Elewa ◽

Marva Malik ◽

Zahidur Arif ◽

Roger Pique-Regi ◽

...

Keyword(s):

Mass Spectrometry ◽

Elongation Rate ◽

Mrna Splicing ◽

Splicing Factor ◽

Splicing Factors ◽

Human Homolog ◽

Termination Factor ◽

Yeast Genes ◽

Nuclear Processes

AbstractThe yeast termination factor Rat1, and its human homolog Xrn2, have been implicated in multiple nuclear processes. Here we report a novel role of Rat1 in mRNA splicing. Rat1 mutants display increased levels of unspliced transcripts. Accumulation of unspliced transcripts was not due to a failure to degrade unspliced mRNA, disruption of termination or an increased elongation rate in Rat1 mutants. ChIP-Seq analysis revealed Rat1 crosslinking to the introns of a subset of yeast genes. Mass spectrometry and coimmunoprecipitation revealed interaction of Rat1 with the Clf1, Isy1, Yju2, Prp43, and Sub2 splicing factors. Furthermore, recruitment of the Prp2 splicing factor on the intron was compromised in the Rat1 mutant. Based on these findings we propose that Rat1 has a novel role in splicing of a subset of mRNA in budding yeast.

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