Biology subjects

Sanyal, S.

Publications and source records attributed to Sanyal, S..

At least 19 recordsLinked to original sources

bioRxiv2026

miRNA-mediated regulation of lineage plasticity in YY1 knockout pro-B cells

Yin Yang 1 (YY1) is a multifunctional transcription factor involved in chromatin organization and gene regulation. While the mechanisms by which YY1 controls B cell lineage development have been explored at the transcriptional level, little is known at the post-transcriptional level. To address this, we performed integrated analyses combining bulk transcriptomics, miRNA profiling, and single-cell transcriptomics to identify YY1-dependent regulatory networks at the pro-B cell stage. YY1 knockout (KO) in pro-B cells leads to reduced B-lineage commitment and activation of genes associated with alternative hematopoietic fates. Our integrative analyses suggest that these changes are organized in part through coordinated miRNA-mRNA regulatory networks. In wild-type (WT) pro-B cells, miRNAs such as miR-10a-5p, miR-674-5p, and miR-21a-5p maintain B cell identity by suppressing RNAs linked to other lineages. In contrast, in YY1 KO pro-B cells increased expression of miRNAs including miR-15b-5p, miR-342-5p, and miR-34a-5p target pathways required for B cell development, proliferation, and survival thus reducing B lineage identity. Together, these findings suggest that YY1 preserves B cell identity through coordinated regulation of transcriptional and post-transcriptional programs, with YY1-dependent miRNA networks contributing to the maintenance of B cell-associated gene expression and restriction of alternative lineage programs. Among these, miR-15b-5p emerged as a central regulator predicted to regulate Bcl6b and E2f family transcription factors that control proliferative and transcriptional programs critical for early B cell development. At single-cell resolution, YY1 KO pro-B cells grown on OP9-DL4 feeders that provide Notch signaling displayed marked transcriptional heterogeneity and loss of pro-B lineage commitment. Pseudotime analysis revealed a branched developmental landscape, with cells diverging toward monocyte, macrophage, and dendritic cell fates rather than a consistent B cell differentiation trajectory. Collectively, these findings establish YY1 as a central regulator of lineage commitment integrating transcriptional and miRNA-mediated post-transcriptional mechanisms to regulate B cell identity.

molecular biology↗

bioRxiv2026

Molecular mechanism of IF1- and IF2-driven translation initiation in bacteria

Bacterial translation initiation is a highly regulated process essential for accurate start codon selection and the assembly of an elongation-competent ribosome. Two initiation factors, 1 (IF1) and 3 (IF3), contribute to quality control for formation of 30S preinitiation complex (30S PIC), while the GTPase IF2 facilitates stable initiator tRNA binding and promotes subunit association. However, the molecular mechanism of IF1 action and the regulatory role of IF2-mediated GTP hydrolysis and inorganic phosphate (Pi) release remain poorly understood. Using ensemble cryo-EM integrated with fast-kinetics, we delineate the translation initiation pathway involving IF1 and IF2. We show that IF1 transiently associates with the 30S subunit and interferes with the formation of multiple inter-subunit bridges. IF2 promotes subunit association by stabilizing the 30S PIC through interactions mediated by its N-terminal domains. IF1 departure happens after or concomitant with GTP hydrolysis, following which the inter-subunit bridges establish. Then Pi release triggers remodeling of IF2 followed by its departure from the 70S initiation complex. These findings reveal how the coordinated interplay of IF1 and IF2 with the ribosome ensures translational fidelity and plays crucial role for formation of elongation-competent 70S.

biochemistry↗

bioRxiv2026

TRIM21 is a molecular rheostat for influenza A virus replication

TRIM21 is a multifunctional E3 ubiquitin ligase and intracellular antibody receptor, yet its role during viral infection remains unclear, with reports describing both antiviral and proviral activities. Here, we show that TRIM21 regulates influenza infection in an expression-dependent manner by functioning as a molecular rheostat rather than a binary restriction factor. This graded activity of TRIM21, which leads to both suppression and promotion of influenza replication, couples linkage-specific ubiquitination of viral nucleoprotein with modulation of innate immune signaling. Additionally, loss of TRIM21 unmasks a compensatory antiviral program centered on PRKDC, which is a ubiquitination target of TRIM21. This positions PRKDC as a latent restriction factor selectively engaged when primary TRIM21 control is lost. Together, these findings reveal a hierarchical and plastic antiviral network in which TRIM21 sets an adjustable threshold for host defense while restraining secondary restriction pathways. This framework highlights the sophisticated layers of regulation of the host ubiquitin-mediated antiviral immunity.

cell biology↗

bioRxiv2025

Association of miR-181a-5p with Lantana camara leaf extract-mediated inhibition of proliferation, survival, and migration in luminal A-type MCF-7 cells and triple-negative type MDA-MB-231 cells

Ethnopharmacological relevanceBreast cancer has a high mortality with increasing chemoresistance and recurrence. Lantana camara has diverse medicinal properties, including anti-cancer potential; however, its role in breast cancer is not well-explored. Aim of the studyThe study aims to elucidate the role of Lantana camara leaf extract in miR-181a-5p-mediated control of proliferation, survival, and migration of breast cancer cells. Material and methodsReal-time PCR was employed for RNA expression studies. Bioinformatic tools were used for identifying miR-181a-5p target mRNAs and seed regions in the 3 prime untranslated region of target mRNAs. miR-181a-5p was overexpressed in cells using transfection method. Flow cytometry was employed for cell cycle and apoptosis assays. Scratch assay was performed to study cell migration. The 3 prime untranslated region of CDKN3 was cloned, and site-directed mutagenesis was employed to mutate miR-181a-5p seed region. Western blot analysis was employed for a reporter assay. ResultsL. camara leaf extract upregulated the expression of miR-181a-5p with concomitant decrease in mRNAs of BCL-2, MCL-1, and CDKN3 in breast cancer cells. Overexpression of miR-181a-5p induced cell death in MCF-7 and MDA-MB-231 cells, and cell death increased in the presence of leaf extract. miR-181a impeded migration in both cell lines in the presence of the extract. Reporter assay confirmed the interaction of miR-181a-5p with 3 prime untranslated region of the CDKN3 mRNA. ConclusionOur study suggests that the extract may play an important role in regulating miR-181a-5p in MCF-7 and MDA-MB-231 cells, and may have important therapeutic potential for breast cancer therapy.

cancer biology↗

bioRxiv2025

Lantana camara leaf extract-mediated suppression of DNA methyltransferase 1 promotes G0/G1 cell cycle arrest and apoptosis, and impedes migration in MDA-MB-231 triple-negative breast cancer cells

BackgroundTriple-negative breast cancer (TNBC) is an aggressive subtype of breast cancer with limited therapeutic options and poor prognosis. DNA methyltransferase 1 (DNMT1) maintains aberrant silencing of tumor suppressor genes, contributing to cancer progression. Our previous work demonstrated that Lantana camara leaf extract induces G0/G1 arrest and apoptosis, while inhibiting migration in MDA-MB-231 TNBC cells (Pal et al., 2024). PurposeThis study investigated the role of DNMT1 in mediating the anticancer effects of Lantana camara extract. Study DesignAn in vitro experimental study was performed using MDA-MB-231 TNBC cells. MethodsCells were treated with the extract, and the expression of DNMT1 was analyzed at the mRNA and protein levels. Expression of tumor suppressor genes was assessed at mRNA level. Functional assays were conducted following DNMT1 overexpression to examine its impact on extract-induced effects. Expression of methyl-CpG binding domain protein 2 (MBD2), histone deacetylase 1 (HDAC1), and histone deacetylase 2 (HDAC2) was evaluated at the mRNA level. ResultsThe extract significantly downregulated DNMT1, resulting in the reactivation of multiple tumor suppressor genes. Overexpression of DNMT1 counteracted the extract-induced reduction in cell viability, reduced G0/G1 arrest, attenuated apoptosis, and enhanced migratory capacity, while suppressing the mRNA expression of tumor suppressor genes. Additionally, the extract downregulated the mRNA expression of MBD2, HDAC1, and HDAC2, suggesting broader modulation of epigenetic regulators. ConclusionSuppression of DNMT1 is a central mechanism underlying the anticancer activity of Lantana camara extract. These findings highlight its potential as a natural epigenetic modulator and a promising therapeutic candidate for TNBC.

cancer biology↗

bioRxiv2025

UCHL3 regulates subgenomic flaviviral RNA condensates to promote virus propagation

In this study we demonstrate a previously uncharacterised post-translational regulatory mechanism governing flavivirus replication through the deubiquitylating enzyme ubiquitin C-terminal hydrolase L3 (UCHL3). Using activity-based protein profiling, we identified UCHL3 as a key cellular factor activated during Zika virus (ZIKV) and dengue virus (DENV) infections. CRISPR-Cas9 knockout experiments demonstrated that UCHL3 deficiency impairs flavivirus replication and viral protein expression across multiple cellular models. The underlying molecular mechanism involves UCHL3-mediated stabilisation of subgenomic flaviviral RNA (sfRNA)-containing biomolecular condensates. Through biotinylated sfRNA-interactome capture assays, we show that UCHL3 physically interacts with sfRNA-containing ribonucleoprotein complexes alongside G3BP1. Importantly, UCHL3 depletion triggers inappropriate RNase L activation, leading to sfRNA relocalisation from protective P-bodies to degradative compartments, such as RNase L-induced bodies (RLBs) as reported previously, resulting in viral RNA decay. Our rescue experiments confirmed that RNase L knockdown restores viral replication in UCHL3-deficient cells. This pro-viral effect of UCHL3 operates through interferon-independent mechanisms, as demonstrated by persistent replication defects even upon exogenous interferon treatment. This work therefore identifies UCHL3 as a molecular switch controlling the balance between pro-viral and antiviral RNA condensates, representing a promising host dependency factor for broad-spectrum flavivirus intervention strategies.

cell biology↗

bioRxiv2025

Remodelled cholesteryl ester enriched lipid droplets fuel flavivirus morphogenesis

Flaviviruses such as dengue and Zika viruses extensively remodel host cell membranes to create specialised replication organelles, but the role of lipid metabolism to generate them remain poorly understood. Through systematic screens of fatty acyl transferase enzymes (MBOAT and zDHHC families) and complementary approaches including CRISPR/Cas9 gene deletions, pharmacological inhibition, proteomics, and photo-crosslinkable cholesterol analogues, we identified cholesteryl ester-enriched lipid droplets (CE-LDs) as critical host components required for flavivirus infection. CE-LD formation is mediated by Sterol O-acyltransferases 1 and 2 (SOAT1/SOAT2), whose activities were upregulated early during infection, coinciding with increased CE-LD formation and transition to liquid crystalline phases. Genetic deletion or pharmacological inhibition of either enzyme resulted in a dramatic [~]100-fold reduction in viral production. Mechanistically, CE-LDs display distinct proteomic signatures, enriched in fatty acid remodelling enzymes, GTPases, and lipid transport proteins. Photo-crosslinking experiments demonstrated direct interactions between LD-derived cholesterol and viral prM, capsid and NS1. Disrupting CE-LD formation via SOAT1/2-deficiency resulted in defective, viral RNA-free replication organelles and complete absence of immature virions. Supporting the physiological and clinical relevance of viral LD exploitation, analysis in iPSC-derived macrophages mirrored findings in Huh7 cells, and dengue patients from a Sri Lankan cohort revealed that central obesity significantly increased the risk of severe dengue haemorrhagic fever. This study establishes CE-LDs as essential host metabolic hubs that enable flavivirus morphogenesis and identifies host LD metabolism as a promising therapeutic target for combating flavivirus infections.

cell biology↗

bioRxiv2024

Structural mechanism of FusB-mediated rescue from fusidic acid inhibition of protein synthesis

Antibiotic resistance protein FusB rescues protein synthesis from inhibition by fusidic acid (FA), which locks elongation factor G (EF-G) to the ribosome after GTP hydrolysis. Here, we present time-resolved single-particle cryo-EM structures explaining the mechanism of FusB-mediated rescue. FusB binds to the FA-trapped EF-G on the ribosome, causing large-scale conformational changes of EF-G that break ribosome interactions. This leads to dissociation of EF-G from the ribosome, followed by FA release. We also observe two independent binding sites of FusB on the classical-state ribosome, overlapping with the binding site of EF-G to each of the ribosomal subunits, yet not inhibiting tRNA delivery. Our results reveal an intricate resistance mechanism involving specific interactions of FusB with both EF-G and the ribosome, and a non-canonical release pathway of EF-G.

molecular biology↗

bioRxiv2024

Δ133p53 and Δ160p53 isoforms of the tumor suppressor protein p53 exert dominant-negative effect primarily by co-aggregation

p53 is a tumor suppressor protein with multiple isoforms with shared or specific functions. However, two of its isoforms, {Delta}133p53 and {Delta}160p53, with large N-terminal deletions, can cause cancer. These isoforms exert a dominant-negative effect on full-length p53 (FLp53), although the precise molecular mechanisms are unknown. Here, we investigate the mechanisms of action of {Delta}133p53 and {Delta}160p53 isoforms using chromatin immunoprecipitation, luciferase expression, subcellular fractionation, immunofluorescence assays, and apoptotic caspase activity assay. Our study elucidates that these DNA-binding deficient p53 isoforms form hetero-tetrameric complexes with FLp53 and disrupt FLp53s DNA binding and transcriptional activities when present in a higher proportion than FLp53 in the tetramer. However, these structurally unstable isoforms promote vigorous protein aggregation involving FLp53, disrupting its structure and sequestering it in the cytoplasmic and nuclear aggregates, thereby limiting its availability to function as a transcription activator protein. Thus, co-aggregation of {Delta}133p53 and {Delta}160p53 with FLp53, rather than hetero-tetramerization, is likely the primary factor contributing to their dominant-negative effect. Modulating the stability and aggregation of p53 isoforms could be a novel strategy for cancer therapy.

cancer biology↗

bioRxiv2024

Unusual lineage plasticity revealed by YY1 knockout in pro-B cells

During B cell development, cells progress through multiple developmental stages with the pro-B cell stage defining commitment to the B cell lineage. YY1 is a ubiquitous transcription factor that is capable of both activation and repression functions. We find here that knockout of YY1 at the pro-B cell stage eliminates B lineage commitment. YY1 knockout pro-B cells can generate T lineage cells in vitro using the OP9- DL4 feeder system, as well as in vivo after injection into sub-lethally irradiated Rag1-/- mice. These T lineage-like cells lose their B lineage transcript profile and gain a T cell lineage profile. Single cell-RNA-seq experiments showed that as YY1 knockout pro-B cells transition into T lineage cells, various cell clusters adopt transcript profiles representing a multiplicity of hematopoietic lineages indicating unusual lineage plasticity. Given the ubiquitous nature of YY1 and its dual activation and repression functions, YY1 likely regulates commitment in multiple cell lineages.

developmental biology↗

bioRxiv2023

GDF15 is a dynamic biomarker of the Integrated Stress Response in the central nervous system

AimCharacterize Growth Differentiation Factor 15 (GDF15) as a secreted biomarker of the Integrated Stress Response (ISR) within the Central Nervous System (CNS). MethodsWe determined GDF15 levels utilizing in vitro and in vivo neuronal systems wherein the ISR was activated. Primarily, we used the murine model of Vanishing White Matter disease (VWMD), a neurological disease driven by persistent ISR in the CNS, to establish a link between levels of GDF15 in the cerebrospinal fluid (CSF) and ISR gene expression signature in the CNS. GDF15 was also determined in the CSF of VWM patients. ResultsGDF15 expression was increased concomitant to ISR activation in stress-induced primary astrocytes as well as in retinal ganglion cells following optic nerve crush, while treatment with 2Bact, a specific eIF2B activator, suppressed both the ISR and GDF15. In the VWMD model, CSF GDF15 levels corresponded with the magnitude of the ISR and were reduced by 2BAct. In VWM patients, mean CSF GDF15 was elevated >20-fold as compared to healthy controls, whereas plasma GDF15 was undifferentiated. ConclusionsThese data suggest that CSF GDF15 is a dynamic marker of ISR activation in the CNS and may serve as a pharmacodynamic biomarker for ISR-modulating therapies.

neuroscience↗

bioRxiv2023

Second messenger c-di-AMP regulates multiple antibiotic sensitivity pathways in Mycobacterium smegmatis by discrete mechanisms

One of the debilitating causes of high mortality in the case of tuberculosis and other bacterial infections is the resistance development against standard drugs. There are limited studies so far to describe how a bacterial second messenger molecule can directly participate in distinctive antibiotic tolerance characteristics of a cell in a mechanism-dependent manner. Here we show that intracellular cyclic di-AMP (c-di-AMP) concentration can modulate drug sensitivity of Mycobacterium smegmatis by directly interacting with either a protein effector or with the 5-UTR regions in mRNA of the genes and thus causing transcriptional downregulation of important genes in the pathways. We studied four antibiotics with different mechanisms of action: rifampicin, ciprofloxacin, erythromycin, and tobramycin and subsequently found that the level of drug sensitivity of the bacteria is directly proportional to the c-di-AMP concentration inside the cell. Further, we unraveled the underlying molecular mechanisms to delineate the specific genes and pathways regulated by c-di-AMP and hence result in differential drug sensitivity in M. smegmatis. Thus, our findings of c-di-AMP messenger controlling drug resistance phenotypes of mycobacteria against four different classes of antibiotics is a unique observation that will contribute to scientific advancement in the field. One Sentence SummaryHere we describe how second messenger c-di-AMP modulates the antibiotic sensitivity and resistance profile of M. smegmatis by diverse mechanisms.

microbiology↗

bioRxiv2023

PARP14 is a PARP with both ADP-ribosyl transferase and hydrolase activities

PARP14 is a mono-ADP-ribosyl transferase involved in the control of immunity, transcription and DNA replication stress management. However, little is known about the ADP-ribosylation activity of PARP14, including its substrate specificity or how PARP14-dependent ADP-ribosylation is reversed. Here we show that PARP14 is dual function enzyme with both ADP-ribosyl transferase and hydrolase activity acting on both protein and nucleic acid substrates. In particular, we show that the PARP14 macrodomain 1 is an active ADP-ribosyl hydrolase. We also demonstrate hydrolytic activity for the first macrodomain of PARP9. We reveal that expression of a PARP14 mutant with the inactivated macrodomain 1 results in a dramatic increase in mono(ADP-ribosyl)ation of proteins in human cells, including PARP14 itself and antiviral PARP13. Moreover, we demonstrate that the closely related hydrolytically active macrodomain of SARS2 Nsp3, Mac1, efficiently reverses PARP14 ADP-ribosylation in vitro and in cells, supporting the evolution of viral macrodomains to counteract PARP14-mediated antiviral response. TeaserPARP14 is an antiviral PARP that combines ADP-ribosylation writer, reader and eraser functions in one polypeptide.

cell biology↗

bioRxiv2023

Characterization of the small Arabidopsis thaliana GTPase and ADP-ribosylation factor-like 2 protein TITAN5

Small GTPases function by conformational switching ability between GDP- and GTP-bound states in rapid cell signaling events. The ADP-ribosylation factor (ARF) family is involved in vesicle trafficking. Though evolutionarily well conserved, little is known about ARF and ARF-like GTPases in plants. Here, we characterized biochemical properties and cellular localization of the essential small ARF-like GTPase TITAN 5/HALLIMASCH/ARL2/ARLC1 (hereafter termed TTN5) from Arabidopsis thaliana. Two TTN5 variants were included in the study with point mutations at conserved residues, suspected to be functional for nucleotide exchange and GTP hydrolysis, TTN5T30N and TTN5Q70L. We found that TTN5 had a very rapid intrinsic nucleotide exchange capacity with a conserved nucleotide switching mechanism. TTN5 acted as a non-classical small GTPase with a remarkably low GTP hydrolysis activity, suggesting it is likely present in GTP-loaded active form in the cell. We analyzed signals from yellow fluorescent protein (YFP)-tagged TTN5 and from in situ immunolocalization of hemagglutine-tagged HA3-TTN5 in Arabidopsis seedlings and in a transient expression system. Together with colocalization using endomembrane markers and pharmacological treatments the microscopic analysis suggests that TTN5 can be present at the plasma membrane and dynamically associated with membranes of vesicles, Golgi stacks and multivesicular bodies. While the TTN5Q70L variant showed similar GTPase activities and localization behavior as wild-type TTN5, the TTN5T30N mutant differed in some aspects. Hence, the unusual capacity of rapid nucleotide exchange activity of TTN5 is linked with cell membrane dynamics, likely associated with vesicle transport pathways in the endomembrane system. HighlightsO_LIThe small ARF-like GTPase TTN5 has a very rapid intrinsic nucleotide exchange capacity with a conserved nucleotide switching mechanism C_LIO_LIBiochemical data classified TTN5 as a non-classical small GTPase, likely present in GTP-loaded active form in the cell C_LIO_LIYFP-TTN5 is dynamically associated with vesicle transport and different processes of the endomembrane system, requiring the active form of TTN5 C_LI

plant biology↗

bioRxiv2023

Mutation nsp6 L232F associated with MERS-CoV zoonotic transmission confers higher viral replication in human respiratory tract cultures ex-vivo

Middle East respiratory syndrome coronavirus (MERS-CoV) causes zoonotic disease. Dromedary camels are the source of zoonotic infection. We identified a mutation of amino acid leucine to phenylalanine in the codon 232 position of the non-structural protein 6 (nsp6) (nsp6 L232F) that is repeatedly associated with zoonotic transmission. We generated a pair of isogenic recombinant MERS-CoV with nsp6 232L and 232F residues, respectively, and showed that the nsp6 L232F mutation confers higher replication competence in ex-vivo culture of human nasal and bronchial tissues and in lungs of mice experimentally infected in-vivo. Mechanistically, the nsp6 L232F mutation appeared to modulate autophagy and was associated with higher exocytic virus egress, while innate immune responses and zippering activity of the endoplasmic reticulum remained unaffected. Our study suggests that MERS-CoV nsp6 may contribute to viral adaptation to humans. This highlights the importance of continued surveillance of MERS-CoV in both camels and humans. ImportanceViral host adaptation plays an important role in zoonotic transmission of coronaviruses. For MERS-CoV that widely circulates in dromedary camels from Arabian Peninsula, camel-to human transmissions are ongoing, raising the possibility of human adaptive evolution for MERS-CoV. Here, we analysed MERS-CoV sequences and identified an amino acid mutation L232F in nsp6 to occur repeatedly in human MERS-CoV over the years since the first outbreak in 2012. We found the nsp6 L232F confers increase viral replication in-vitro, in ex-vivo upper human respiratory tract cultures and in mice, using a reverse genetics approach. Our results showed the nsp6 L232F may be advantageous for MERS-CoV to replicate in humans. This study highlighted a human adaptation of MERS-CoV and a need for continued surveillance of MERS-CoV to identify any further adaptations in humans, which may be relevant to the pandemic potential of MERS-CoV.

microbiology↗

bioRxiv2023

Effect of Lantana camara ethanolic leaf extract on survival and migration of MDA-MB-231 triple negative breast cancer cell line

IntroductionBreast cancer is a leading cause of cancer-related death worldwide. Lantana camara has been reported to cure a number of ailments, with few studies showing its cytotoxic effects on breast cancer cells. However, the impact of Lantana camara on triple negative breast cancer cells is largely obscure to date. The present study investigated the effect of ethanolic extract of Lantana camara leaves on the triple negative breast cancer cell line, MDA-MB-231. MethodsCytotoxic effect of the extract on the cells was determined by cell survival assay. Cell cycle phase distribution was analysed using flow cytometry. To study the effect on nuclear morphology, nuclear stained cells were visualized using epifluorescence microscopy. The induction of apoptosis and generation of reactive oxygen species was conducted using flow cytometry. Cellular migration was studied by performing wound healing assay. Real-time polymerase chain reaction was done to determine the mRNA levels of some key genes. ResultsLantana camara leaf extract induced cytomorphological changes and growth inhibitory effect on MDA-MB-231 cells in a dose-dependent manner. The extract also induced G0/G1 cell cycle arrest and nuclear condensation. Flow cytometry analysis confirmed cell death by apoptosis. Lantana camara leaf extract also reduced the migration of MDA-MB-231 cells. mRNA expression levels also supported the above observations. ConclusionsThis study demonstrates the efficacy of the extract to induce growth-inhibitory and anti-migratory effects on MDA-MB-231 cells. Our results thus suggest that Lantana camara leaf extract can be considered as a potent source of chemotherapeutic agents for triple negative breast cancer.

cancer biology↗

bioRxiv2022

A system for inducible mitochondria-specific protein degradation in vivo

Targeted protein degradation systems developed for eukaryotes employ cytoplasmic machineries to perform proteolysis. This has prevented mitochondria-specific analysis of genome maintaining proteins that localize to both mitochondria and nucleus. Here, we present an inducible mitochondria-specific protein degradation system in Saccharomyces cerevisiae based on the Mesoplasma florum Lon (mf-Lon) protease and its corresponding ssrA tag (called PDT). We show that mitochondrially targeted mf-Lon protease efficiently and selectively degrades a PDT-tagged reporter protein localized to the mitochondrial matrix. The degradation can be induced by depleting adenine from the medium and tuned by altering the promoter strength of the MF-LON gene. Finally, we demonstrate that mf-Lon degrades endogenous, dually localized proteins inside mitochondria. In summary, our system is an efficient tool for analysis of intricate mitochondria-nuclear crosstalk essential for proper mitochondrial function. One-Sentence SummaryMitochondria-specific protein degradation of dually localized proteins

cell biology↗

bioRxiv2021

Ring Finger Protein 213 Assembles into a Sensor for ISGylated Proteins with Antimicrobial Activity

ISG15 is an interferon-stimulated, ubiquitin-like protein that can conjugate to substrate proteins (ISGylation) to counteract microbial infection, but the underlying mechanisms remain elusive. Here, we used a viral-like particle trapping technology to identify ISG15-binding proteins and discovered Ring Finger Protein 213 (RNF213) as an ISG15 interactor and cellular sensor of ISGylated proteins. RNF213 is a poorly-characterized, interferon-induced megaprotein that is frequently mutated in Moyamoya disease, a rare cerebrovascular disorder. We found that interferon induces ISGylation and oligomerization of RNF213 on lipid droplets, where it acts as a sensor for ISGylated proteins. We showed that RNF213 has broad antimicrobial activity in vitro and in vivo, counteracting infection with Listeria monocytogenes, herpes simplex virus 1 (HSV-1), human respiratory syncytial virus (RSV) and coxsackievirus B3 (CVB3), and we observed a striking co-localization of RNF213 with intracellular bacteria. Together, our findings provide novel molecular insights into the ISGylation pathway and reveal RNF213 as a key antimicrobial effector.

cell biology↗