SUMO: cell lineage dependent nuclear localisation of the transcriptional repressor PIE-1 in Caenorhabditis elegans

Phänotypische Analysen der embryonal letalen Mutante ulp-1 (t1530) des Nematoden C.elegans zeigen eine fehlerhafte Spezifizierung der somatischen Gründerzellen MS, C und D in der frühen Embryogenese. Eine zweite pleiotrope Funktion des Gens betrifft die Ausführung der Apoptose und/oder der Phagozytose embryonaler Zellen. Das Gen ulp-1 kodiert für eine SUMO spezifische Protease, die durch Abspaltung des SUMO Proteins eine posttranslationale Modifikation durch SUMO revertiert. Das Protein hat damit eine generelle regulatorische Funktion, die die unabhängigen Phänotypen erklären kann. Durch (Über-)Expression des reifen SUMO Proteins in der ulp-1 Mutante wurde das keimbahnspezifische Protein PIE-1 als ein Zielprotein der SUMOylierung identifiziert. PIE-1 unterdrückt die Transkription in Keimbahnzellen, was essentiell für ihre Spezifizierung ist. Es wurde gezeigt, dass die SUMOylierung von PIE-1 die subzelluläre Lokalisation des Proteins reguliert. Das nicht SUMOylierte Protein liegt im Cytoplasma, das SUMOylierte im Kern vor. Die Entdeckung, dass die Aktivität von PIE-1 durch eine differenzielle Lokalisation im Kern und Cytoplasma reguliert wird, erlaubt es, die Funktion von ulp-1 bei der Spezifizierung der Gründerzellen zu erklären. Die Protease verhindert normalerweise die Kernlokalisierung des nach einer stammzellartigen P-Teilung zurückbleibenden PIE-1 Proteins und damit die generelle Repression der Transkription in der somatischen Zelle. Die Defekte in der ulp-1 (t1530) Mutante entstehen durch eine Repression der zur Expression des Schicksals notwendigen Transkription. Die Analyse der fehlerhaften Apoptose zeigt, dass die nicht phagozytierten Zelltode den Sterbeprozess auf halbem Weg beenden und diese möglicherweise deshalb nicht phagozytiert werden. Da die Inaktivierung eines Gens des Ubiquitin-Pathways (zif-1) zu vergleichbaren morphologischen Veränderungen in den apoptotischen Zellen führt, könnte die SUMOylierung hier antagonistisch zur Ubiquitinierung wirken.A phenotypic analysis of the embryonic lethal mutant ulp-1 (t1530) shows a misspecification of the somatic founder cells MS, C and D during early embryogenesis. A second pleiotropic function of the gene is detected in the apoptosis of embryonic cells. The gene ulp-1 encodes a SUMO specific protease, which reverts the posttranslational modification mediated by SUMO. Therefore, the protein has a general regulatory function, which could explain the independent phenotypes of the mutant. The germ line specific protein PIE-1 was identified as a potential target of the SUMOylation by (over-)expression of mature SUMO protein in the ulp-1 mutant. PIE-1 represses the transcription in the germ line blastomeres, which is essential for their specification. Here it is shown, that SUMOylation of PIE-1 regulates the subcellular localisation of the protein. The SUMOylated protein localises to the nucleus, whereas the unmodified protein remains in the cytoplasm. The discovery that the activity of PIE-1 is regulated by a differential localisation between the nucleus and the cytoplasm allows to explain the function of ULP-1 during the specification of the founder cells. Normally, the protease prevents the remaining PIE-1 protein after each division of the germ line precursor cells to localise to the nucleus in the somatic blastomere and therefore to repress the transcription in these cells. The misspecification of the early blastomeres, seen in the ulp-1 (t1530) mutant, is due to the ectopic repression of transcription in the somatic blastomeres. The analysis of the defects in the apoptotic cells shows that the cells do not execute the complete cell death pathway. Therefore, apoptotic cells are not phagocytosed. Inactivation of a gene (zif-1), which is involved in the ubiquitin pathway, results in comparable morphological changes in the apoptotic cells. This suggests that the SUMOylation could function in this case in an antagonistic manner to the ubiquitination

Target-Mediated Protection of Endogenous MicroRNAs in C. elegans

SummaryMicroRNAs (miRNAs) are tightly regulated through transcriptional and posttranscriptional mechanisms, including degradation by nucleases. Here, we report that in C. elegans, target mRNAs can protect their cognate miRNAs from degradation in vivo. We show that the let-7(n2853) mutation destabilizes the mature let-7 miRNA by impairing this protection. Moreover, presence of a cognate target or depletion of the xrn-1 (XRN1) or xrn-2 (XRN2/Rat1p) exoribonucleases enforces accumulation of certain miRNA passenger (miR∗) strands. Thus, following biased miRNA strand loading into Argonaute, elimination of nonfunctional RNAs can further refine miRNA strand selection. Conversely, by aligning the levels of miRNAs with those of their targets, the opposing activities of mature miRNA degradation and target-mediated miRNA protection (TMMP) may enable dynamic expression of either mature strand of a pre-miRNA, and evolution of miRNAs. Thus, it seems that mRNAs are more than inert targets and function with miRNAs in a network of mutual regulation

Crystal structures of the gold NHC complex bis-(4-bromo-1,3-di-ethyl-imidazol-2-yl-idene)gold(I) iodide and its 1:1 adduct with trans-bis-(4-bromo-1,3-diethyl-imidazol-2-yl-idene)di-iodido-gold(III) iodide

The first title compound, [Au(C7H11BrN2)2]I, crystallizes in the space group P without imposed symmetry. The cations and anions are linked to form chains by Br⋯I⋯Br halogen-bond linkages. The second title compound, [Au(C7H11BrN2)2][AuI2(C7H11BrN2)2]I2, is an adduct of the first and its formally I2-oxidized AuIII analogue. It also crystallizes in space group P , whereby both gold atoms occupy inversion centres. The extended structure is a reticular layer involving Br⋯I⋯Br and I⋯I⋯Au linkages

Oncogenic potential of a C.elegans cdc25 gene is demonstrated by a gain-of-function allele

In multicellular organisms, developmental programmes must integrate with central cell cycle regulation to co-ordinate developmental decisions with cell proliferation. Hyperplasia caused by deregulated proliferation without significant change to other aspects of developmental behaviour is a probable step towards full oncogenesis in many malignancies. CDC25 phosphatase promotes progression through the eukaryotic cell cycle by dephosphorylation of cyclin-dependent kinase and, in humans, different cdc25 family members have been implicated as potential oncogenes. Demonstrating the direct oncogenic potential of a cdc25 gene, we identify a gain-of-function mutant allele of the Caenorhabditis elegans gene cdc-25.1 that causes a deregulated proliferation of intestinal cells resulting in hyperplasia, while other aspects of intestinal cell function are retained. Using RNA-mediated interference, we demonstrate modulation of the oncogenic behaviour of this mutant, and show that a reduction of the wild-type cdc-25.1 activity can cause a failure of proliferation of intestinal and other cell types. That gain and loss of CDC-25.1 activity has opposite effects on cellular proliferation indicates its critical role in controlling C.elegans cell number

Gold Metallodrugs to Fight the Corona Virus: Inhibitory Effects on the SpikeACE2 Interaction and on PLpro Protease Activity by Auranofin and Gold Organometallics

Gold complexes have a long tradition in medicine and for many examples antirheumatic, anticancer or anti-infective effects have been confirmed. Here we evaluated the lead compound Auranofin and five selected gold organometallics as inhibitors of two relevant drug targets of severe acute respiratory syndrome coronaviruses (SARS-CoV). The gold metallodrugs were effective inhibitors of the interaction of the SARS-CoV-2 spike protein with the angiotensin converting enzyme 2 (ACE2) host receptor and might thus interfere with the viral entry process. The gold metallodrugs were also efficient inhibitors of the SARS-CoV-1 papain-like protease (PLpro), which is a key enzyme in the viral replication. Taken together, the results of this pilot study suggest further evaluation of gold complexes as SARS-CoV antiviral drugs

Metallodrug Profiling against SARS‐CoV‐2 Target Proteins Identifies Highly Potent Inhibitors of the Spike/ACE2 interaction and the Papain‐like Protease PLpro

International audienceThe global spread of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has called for an urgent need for dedicated antiviral therapeutics. Metal complexes are commonly underrepresented in the compound libraries that are used for screening in drug discovery campaigns, however, there is growing evidence for their role in medicinal chemistry. Based on previous results, we have selected more than 100 structurally diverse metal complexes for a profiling as inhibitors of two relevant SARS-CoV-2 replication mechanisms, namely the interaction of the spike protein with the ACE2 receptor and the papain-like protease PL pro . In addition to many well-established types of mononuclear experimental metallodrugs, the pool of compounds tested was extended to approved metal-based therapeutics such as silver sulfadiazine and thiomersal, as well as polyoxometalates (POMs). Among the mononuclear metal complexes, only a small number of active inhibitors of the spike/ACE2 interaction was identified, with titanocene dichloride as the only strong inhibitor. However, among the gold and silver containing complexes many turned out to be very potent inhibitors of PL pro activity. Highly promising activity against both targets was noted for many POMs. Selected complexes were evaluated in antiviral SARS-CoV-2 assays confirming activity for gold complexes with N -heterocyclic carbene (NHC) or dithiocarbamato ligands, a silver NHC complex, titanocene dichloride as well as a POM. These studies might provide starting points for the design of metal-based SARS-CoV-2 antiviral agents