Biology subjects

Jensen, T. H.

Publications and source records attributed to Jensen, T. H..

15 recordsLinked to original sources

bioRxiv2025

ZAKα is a sensor of mRNA stasis at the ribosomal exit channel

Despite a growing interest in the ribotoxic stress response (RSR), it remains unknown how the upstream p38 and JNK-activating MAP3 kinase ZAK senses translational impairment. Combining Alphafold3 prediction and RNA crosslinking and immunoprecipitation (CLIP), we uncover that ZAK dynamically monitors the mRNA exit channel of elongating ribosomes for mRNA stasis. This is accomplished by ZAK via its direct interactions with the ribosomal proteins RACK1 and RPS27 as well as with the 18S rRNA helix-26. In this conformation, four mRNA-binding peptides in ZAK span across the path of ribosome-exiting mRNA. Progressive elongation effectively threads ZAK off the ribosome, while mRNA stasis stabilizes the interaction allowing for kinase activation. Prolonged binding of ZAK to slow-elongating, stalled and collided ribosomes is associated with sequestration of the inhibitory SAM domain on RACK1, allowing for transient ZAK dimerization, activation loop trans-autophosphorylation and RSR activation. We propose that compromised ribosome processivity constitutes a common ribotoxic stress signal and that ZAK is a ribosome collision-agnostic sensor of such perturbations.

molecular biology↗

bioRxiv2025

Molecular basis of polyadenylated RNA fate determination in the nucleus

Eukaryotic genomes generate a plethora of polyadenylated (pA+) RNAs1,2, that are packaged into ribonucleoprotein particles (RNPs). To ensure faithful gene expression, functional pA+ RNPs, including protein-coding RNPs, are exported to the cytoplasm, while transcripts within non-functional pA+ RNPs are degraded in the nucleus1-4. How cells distinguish these opposing fates remains unknown. The DExD-box ATPase UAP56/DDX39B is a central component of functional pA+ RNPs, promoting their docking to the nuclear pore complex (NPC)-anchored transcription and export complex 2 (TREX-2) (ref.5,6), which triggers transcript release from UAP56 to facilitate export (ref.7,8). Here, we uncover that the Poly(A) tail exosome targeting (PAXT) connection9 harbors its own TREX-2-like module, which releases pA+ RNAs from UAP56 for decay by the nuclear exosome. The core of this module consists of a LENG8-PCID2-SEM1 (LENG8-PS) trimer, which we show is structurally and functionally equivalent to the central GANP-PCID2-SEM1 (GANP-PS) trimer of TREX-2. Mutagenesis and transcriptomic data demonstrate that the nuclear fate of pA+ RNPs is governed by the contending actions of nucleoplasmic PAXT and NPC-associated TREX-2, which interpret RNA-bound UAP56 as a signal for RNA decay or export, respectively. As RNA targets of PAXT are generally short and intron-poor, we propose an overall model for pA+ RNP fate determination, whereby the distinct sub-nuclear localizations of PAXT and TREX-2 govern the degradation of short non-functional pA+ RNAs while allowing export of their longer and functional counterparts.

molecular biology↗

bioRxiv2025

Control of retrotransposon-driven activation of the interferon response by the double-stranded RNA binding protein DGCR8

The type I interferon (IFN) response is the main innate immune pathway against viruses in mammals. This pathway must be tightly regulated to prevent viral spread while avoiding excessive immune responses. Here, we show that inactivation of the double-stranded RNA (dsRNA)-binding protein DGCR8 unleashes the IFN response in human cells. We demonstrate that DGCR8 restricts the accumulation of endogenous dsRNA originating from protein-coding mRNAs that harbour transposable elements (TEs), primarily Alu. We propose that DGCR8 binding to TE-rich mRNAs is essential to resolve dsRNA structures, and in its absence, accumulated dsRNA signals through the RIG-I-like signalling pathway triggering the IFN response. This mechanism is relevant to conditions where DGCR8 expression levels are altered, including the 22q11.2 deletion syndrome (22qDS). Supporting this, we show that 22qDS-derived cells exhibit an exacerbated type I IFN response which inversely correlated with DGCR8 levels. All these together demonstrate the importance of suppressing endogenous TE-dsRNA accumulation to prevent unwanted immune activation and associated disease pathogenesis.

molecular biology↗

bioRxiv2024

DNA-directed termination of mammalian RNA polymerase II

The best-studied mechanism of eukaryotic RNA polymerase II (RNAPII) transcriptional termination involves polyadenylation site-directed cleavage of the nascent RNA. The RNAPII-associated cleavage product is then degraded by XRN2, dislodging RNAPII from the DNA template. In contrast, prokaryotic RNAP and eukaryotic RNAPIII often terminate directly at T-tracts in the coding DNA strand. Here, we demonstrate a similar and omnipresent capability for mammalian RNAPII. XRN2- and T-tract-dependent termination are independent - the latter usually acting when XRN2 cannot be engaged. We show that T-tracts terminate snRNA transcription, previously thought to require the Integrator complex. Importantly, we find genome-wide termination at T-tracts in promoter-proximal regions, but not within protein-coding gene bodies. XRN2-dependent termination dominates downstream of protein-coding genes, but the T-tract process is sometimes employed. Overall, we demonstrate global DNA-directed attrition of RNAPII transcription, suggesting that RNAPs retain the potential to terminate over T-rich sequences throughout evolution.

molecular biology↗

bioRxiv2024

RNA 3' end tailing safeguards cells against products of pervasive transcription termination

Premature transcription termination yields a wealth of unadenylated (pA-) RNA. Although this can be targeted for degradation by the Nuclear EXosome Targeting (NEXT) complex, possible back-up pathways remain poorly understood. Here, we find RNA 3end uridylation and adenylation upon NEXT inactivation. U-tailed RNAs are generally short and modified by the cytoplasmic tailing enzymes, TUT4/7, following their PHAX-dependent nuclear export and prior to their degradation by the cytoplasmic exosome or the exoribonuclease DIS3L2. Longer RNAs are instead adenylated redundantly by enzymes TENT2, PAPOLA and PAPOLG. These transcripts are either degraded via the nuclear Poly(A) tail eXosome Targeting (PAXT) connection or exported by conventional factors and removed by the cytoplasmic exosome in a translation-dependent manner. Failure to do so decreases global translation and induces cell death. We conclude that post-transcriptional 3end modification and removal of excess pA- RNA is achieved by tailing enzymes and export factors shared with productive RNA pathways.

molecular biology↗

bioRxiv2024

Substrate recognition principles for PP2A-B55

The PP2A-B55 phosphatase regulates a plethora of signaling pathways throughout eukaryotes. How PP2A-B55 selects its substrates presents a severe knowledge gap. By integrating AlphaFold modelling with comprehensive high resolution mutational scanning, we show that -helices in substrates bind B55 through an evolutionary conserved mechanism. Despite a large diversity in sequence and composition, these -helices share key amino acid determinants that engage discrete hydrophobic and electrostatic patches. Using deep learning protein design, we generate a specific and potent competitive peptide inhibitor of PP2A-B55 substrate interactions. With this inhibitor, we uncover that PP2A-B55 regulates the nuclear exosome targeting complex by binding to an -helical recruitment module in RBM7. Collectively, our findings provide a framework for the understanding and interrogation of PP2A-B55 in health and disease. One sentence summary-helices in PP2A-B55 substrates bind a conserved pocket on B55 through a common mechanism that is conserved in eukaryotes.

cell biology↗

bioRxiv2023

Structural basis for competitive binding of productive and degradative co-transcriptional effectors to the nuclear cap-binding complex

The nuclear cap-binding complex (CBC) co-ordinates co-transcriptional maturation, transport, or degradation of nascent Pol II transcripts. CBC with its partner ARS2 form mutually exclusive complexes with diverse effectors that promote either productive or destructive outcomes. Combining Alphafold predictions with structural and biochemical validation, we show how effectors NCBP3, NELF-E, ARS2, PHAX and ZC3H18 form competing binary complexes with CBC and how PHAX, NCBP3, ZC3H18 and other effectors compete for binding to ARS2. In ternary CBCA complexes with either PHAX, NCBP3 or ZC3H18, ARS2 is responsible for the initial effector recruitment but inhibits their direct binding to the CBC. We show that in vivo ZC3H18 binding to both CBC and ARS2 is required for nuclear RNA degradation. We propose that recruitment of PHAX to CBC-ARS2 can lead, with appropriate cues, to competitive displacement of ARS2 and ZC3H18 from the CBC, thus promoting a productive rather than a degradative RNA fate.

biochemistry↗

bioRxiv2023

Dual agonistic and antagonistic roles of ZC3H18 provides for co-activation of distinct nuclear RNA decay pathways

The RNA exosome is a versatile ribonuclease. In the nucleoplasm of mammalian cells, it is assisted by its adaptors the Nuclear EXosome Targeting (NEXT) complex and the PolyA eXosome Targeting (PAXT) connection. Via its association with the ARS2 and ZC3H18 proteins, NEXT/exosome is recruited to capped and short unadenylated transcripts. Conversely, PAXT/exosome was considered to target longer and adenylated substrates via their poly(A) tails. Here, mutational analysis of the core PAXT component ZFC3H1 uncovers a separate branch of the PAXT pathway, which targets short adenylated RNAs and relies on a direct ARS2-ZFC3H1 interaction. We further demonstrate that similar acidic-rich short linear motifs of ZFC3H1 and ZC3H18 compete for a common ARS2 epitope. Consequently, while promoting NEXT function, ZC3H18 antagonizes PAXT activity. We suggest that this unprecedented organization of RNA decay complexes provides co-activation of NEXT and PAXT at loci with abundant production of short exosome substrates.

molecular biology↗

bioRxiv2023

mRNA decay can be uncoupled from deadenylation during stress response

The polyadenosine tail (pA-tail) regulates mRNA nuclear export, stability, and translatability. Based on reporter constructs, the prevailing model suggests that pA-tail removal mediated by Ccr4-NOT or PAN2/3 deadenylases is required for mRNA decapping and degradation. Here, we use direct RNA sequencing to track mRNA deadenylation and decay at steady-state and in stress conditions to show a global correlation between deadenylation and decay. Interestingly, codon optimality, previously postulated to dictate mRNA stability, only strongly affects decay of conserved and abundant transcripts, such as coding for ribosomal protein subunits. Degradation of those mRNAs is also accelerated in response to stress. Still, the in-depth analysis revealed that deadenylation is a factor that contributes to degradation but is not indispensable for decapping. We further demonstrate that deadenylation is the fastest for newly made tails depending on polyA-binding protein Pab1. Unexpectedly, decapping initiates on mRNAs of pA-tails of 20-35 adenosines presumably bound by Pab1.

molecular biology↗

bioRxiv2020

Integrator is a genome-wide attenuator of non-productive transcription

Termination of RNA polymerase II (RNAPII) transcription in metazoans relies largely on the Cleavage and Polyadenylation (CPA) and Integrator (INT) complexes originally found to act at the ends of protein-coding and snRNA genes, respectively. Here we monitor CPA- and INT-dependent termination activities genome-wide, including over 8000 previously unannotated transcription units (TUs), that produce unstable RNA. We verify the global activity of CPA, that occurs at pA sites indiscriminately of their positioning relative to the TU promoter. We also identify a global activity of INT, which is, however, largely sequence-independent and restricted to a ~3 kb promoter-proximal region. Our analyses suggest two functions of genome-wide INT activity; it dampens transcriptional output from weak promoters and it provides quality-control of RNAPII complexes, that are unfavorably configured for transcriptional elongation. We suggest that the function of INT in stable snRNA production is an exception from its general cellular role, attenuation of non-productive transcription.

cell biology↗

bioRxiv2020

NCBP3 is a productive mRNP component

The nuclear Cap Binding Complex (CBC), consisting of Nuclear Cap Binding Protein 1 (NCBP1) and 2 (NCBP2), associates with the nascent 5’cap of RNA polymerase II transcripts and impacts RNA fate decisions. Recently, the C17orf85 protein, also called NCBP3, was suggested to form an alternative CBC by replacing NCBP2. However, applying protein-protein interaction screening of NCBP1, 2 and 3, we find that the interaction profile of NCBP3 is distinct. Whereas NCBP1 and 2 identify known CBC interactors, NCBP3 primarily interacts with components of the Exon Junction Complex (EJC) and the TRanscription and EXport (TREX) complex. NCBP3-EJC association in vitro and in vivo requires EJC core integrity and the in vivo RNA binding profiles of EJC and NCBP3 overlap. We further show that NCBP3 competes with the RNA degradation factor ZC3H18 for binding CBC-bound transcripts, and that NCBP3 positively impacts the nuclear export of polyadenylated RNAs and the expression of large multi-exonic transcripts. Collectively, our results place NCBP3 with the EJC and TREX complexes in supporting the productive fate of mRNA.Competing Interest StatementThe authors have declared no competing interest.View Full Text

molecular biology↗

bioRxiv2020

Affinity proteomic dissection of the human nuclear cap-binding-complex interactome

A 5, 7-methylguanosine cap is a quintessential feature of RNA polymerase II-transcribed RNAs, and a textbook aspect of co-transcriptional RNA processing. The cap is bound by the cap-binding complex (CBC), canonically consisting of nuclear cap-binding proteins 1 and 2 (NCBP1/2). The CBC has come under renewed investigative interest in recent years due to its participation in RNA-fate decisions via interactions with RNA productive factors as well as with adapters of the degradative RNA exosome - including the proteins SRRT (a.k.a. ARS2) and ZC3H18, and macromolecular assemblies such as the nuclear exosome targeting (NEXT) complex and the poly(A) exosome targeting (PAXT) connection. A novel cap-binding protein, NCBP3, was recently proposed to form an alternative, non-canonical CBC together with NCBP1, and to interact with the canonical CBC along with the protein SRRT. The theme of post-transcriptional RNA fate, and how it relates to co-transcriptional ribonucleoprotein assembly is abundant with complicated, ambiguous, and likely incomplete models. In an effort to clarify the compositions of NCBP1-, 2-, and 3-related macromolecular assemblies, including their intersections and differences, we have applied an affinity capture-based interactome screening approach, where the experimental design and data processing have been modified and updated to identify interactome differences between targets under a range of experimental conditions, in the context of label-free quantitative mass spectrometry. This study generated a comprehensive view of NCBP-protein interactions in the ribonucleoprotein context and demonstrates the potential of our approach to benefit the interpretation of complex biological pathways.

biochemistry↗

bioRxiv2019

Circular RNA ZNF827 tunes neuronal differentiation by facilitating transcriptional repression of Neuronal Growth Factor Receptor

Circular RNAs are important for many cellular processes but their mechanisms of action remain poorly understood. Here, we map circRNA inventories of mouse embryonic stem cells, neuronal progenitor cells and differentiated neurons and identify hundreds of highly expressed circRNAs. By screening several candidate circRNAs for a potential function in neuronal differentiation, we find that circZNF827 represses expression of key neuronal markers, suggesting that this molecule negatively regulates neuronal differentiation. Among 760 tested genes linked to known neuronal pathways, knockdown of circZNF827 deregulates expression of numerous genes including nerve growth factor receptor (NGFR), which becomes transcriptionally upregulated to enhance NGF signalling. We identify a circZNF827-nucleated transcription-repressive complex containing hnRNP-K/L proteins and show that knockdown of these factors strongly augments NGFR regulation. Finally, we show that ZNF827 protein is part of the mRNP complex, suggesting a functional co-evolution of a circRNA and the protein encoded by its linear pre-mRNA host.

molecular biology↗

bioRxiv2019

The lncRNA NEAT1_1 is dispensable for normal tissue homeostasis and cancer cell growth

NEAT1 is one of the most studied lncRNAs, in part because its silencing in mice causes defects in mammary gland development and corpus luteum formation, and protects them from skin cancer development. Moreover, depleting NEAT1 in established cancer cell lines reduces growth and sensitizes cells to DNA damaging agents. However, NEAT1 produces two isoforms and because the short isoform, NEAT1_1, completely overlaps the 5 part of the long NEAT1_2 isoform, the respective contributions of each of the isoforms to these phenotypes has remained unclear. Whereas NEAT1_1 is highly expressed in most tissues, NEAT1_2 is the central architectural component of paraspeckles, which are nuclear bodies that assemble in specific tissues and cells exposed to various forms of stress. Using dual RNA-FISH to detect both NEAT1_1 outside of paraspeckles and NEAT1_2/NEAT1 inside this nuclear body, we report herein that NEAT1_1 levels are dynamically regulated during the cell cycle and targeted for degradation by the nuclear RNA exosome. Unexpectedly, however, cancer cells engineered to lack NEAT1_1, but not NEAT1_2, do not exhibit cell cycle defects. Moreover, Neat1_1-specific knockout mice do not exhibit the phenotypes observed in Neat1-deficient mice. We propose that NEAT1 functions are mainly, if not exclusively, attributable to NEAT1_2 and, by extension, to paraspeckles.\n\nO_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=200 SRC=\"FIGDIR/small/574582_ufig1.gif\" ALT=\"Figure 1\">\nView larger version (54K):\norg.highwire.dtl.DTLVardef@1ceaf78org.highwire.dtl.DTLVardef@6203b2org.highwire.dtl.DTLVardef@e0d5c9org.highwire.dtl.DTLVardef@f37f92_HPS_FORMAT_FIGEXP M_FIG Graphical abstract C_FIG

molecular biology↗

bioRxiv2017

Transcription start site analysis reveals widespread divergent transcription in D. melanogaster and core promoter encoded enhancer activities

Mammalian gene promoters and enhancers share many properties. They are composed of a unified promoter architecture of divergent transcripton initiation and gene promoters may exhibit enhancer function. However, it is currently unclear how expression strength of a regulatory element relates to its enhancer strength and if the unifying architecture is conserved across Metazoa. Here we investigate the transcription initiation landscape and its associated RNA decay in D. melanogaster. Surprisingly, we find that the majority of active gene-distal enhancers and a considerable fraction of gene promoters are divergently transcribed. We observe quantitative relationships between enhancer potential, expression level and core promoter strength, providing an explanation for indirectly related histone modifications that are reflecting expression levels. Lowly abundant unstable RNAs initiated from weak core promoters are key characteristics of gene-distal developmental enhancers, while the housekeeping enhancer strengths of gene promoters reflect their expression strengths. The different layers of regulation mediated by gene-distal enhancers and gene promoters are also reflected in chromatin interaction data. Our results suggest a unified promoter architecture of many D. melanogaster regulatory elements, that is universal across Metazoa, whose regulatory functions seem to be related to their core promoter elements.

genomics↗