The HTLV-1 Tax protein binding domain of cyclin-dependent kinase 4 (CDK4) includes the regulatory PSTAIRE helix

BACKGROUND: The Tax oncoprotein of human T-cell leukemia virus type 1 (HTLV-1) is leukemogenic in transgenic mice and induces permanent T-cell growth in vitro. It is found in active CDK holoenzyme complexes from adult T-cell leukemia-derived cultures and stimulates the G1- to-S phase transition by activating the cyclin-dependent kinase (CDK) CDK4. The Tax protein directly and specifically interacts with CDK4 and cyclin D2 and binding is required for enhanced CDK4 kinase activity. The protein-protein contact between Tax and the components of the cyclin D/CDK complexes increases the association of CDK4 and its positive regulatory subunit cyclin D and renders the complex resistant to p21(CIP )inhibition. Tax mutants affecting the N-terminus cannot bind cyclin D and CDK4. RESULTS: To analyze, whether the N-terminus of Tax is capable of CDK4-binding, in vitro binding -, pull down -, and mammalian two-hybrid analyses were performed. These experiments revealed that a segment of 40 amino acids is sufficient to interact with CDK4 and cyclin D2. To define a Tax-binding domain and analyze how Tax influences the kinase activity, a series of CDK4 deletion mutants was tested. Different assays revealed two regions which upon deletion consistently result in reduced binding activity. These were isolated and subjected to mammalian two-hybrid analysis to test their potential to interact with the Tax N-terminus. These experiments concurrently revealed binding at the N- and C-terminus of CDK4. The N-terminal segment contains the PSTAIRE helix, which is known to control the access of substrate to the active cleft of CDK4 and thus the kinase activity. CONCLUSION: Since the N- and C-terminus of CDK4 are neighboring in the predicted three-dimensional protein structure, it is conceivable that they comprise a single binding domain, which interacts with the Tax N-terminus

Connexin30.2:<i>In vitro</i> interaction with connexin36 in hela cells and expression in AII amacrine cells and intrinsically photosensitive ganglion cells in the mouse retina

Electrical coupling via gap junctions is an abundant phenomenon in the mammalian retina and occurs in all major cell types. Gap junction channels are assembled from different connexin subunits, and the connexin composition of the channel confers specific properties to the electrical synapse. In the mouse retina, gap junctions were demonstrated between intrinsically photosensitive ganglion cells and displaced amacrine cells but the underlying connexin remained undetermined. In the primary rod pathway, gap junctions play a crucial role, coupling AII amacrine cells among each other and to ON cone bipolar cells. Although it has long been known that connexin36 and connexin45 are necessary for the proper functioning of this most sensitive rod pathway, differences between homocellular AII/AII gap junctions and AII/ON bipolar cell gap junctions suggested the presence of an additional connexin in AII amacrine cells. Here, we used a connexin30.2-lacZ mouse line to study the expression of connexin30.2 in the retina. We show that connexin30.2 is expressed in intrinsically photosensitive ganglion cells and AII amacrine cells. Moreover, we tested whether connexin30.2 and connexin36 – both expressed in AII amacrine cells – are able to interact with each other and are deposited in the same gap junctional plaques. Using newly generated anti-connexin30.2 antibodies, we show in HeLa cells that both connexins are indeed able to interact and may form heteromeric channels: both connexins were co-immunoprecipitated from transiently transfected HeLa cells and connexin30.2 gap junction plaques became significantly larger when co-expressed with connexin36. These data suggest that connexin36 is able to form heteromeric gap junctions with another connexin. We hypothesize that co-expression of connexin30.2 and connexin36 may endow AII amacrine cells with the means to differentially regulate its electrical coupling to different synaptic partners

Extreme disorder in an ultrahigh-affinity protein complex

Molecular communication in biology is mediated by protein interactions. According to the current paradigm, the specificity and affinity required for these interactions are encoded in the precise complementarity of binding interfaces. Even proteins that are disordered under physiological conditions or that contain large unstructured regions commonly interact with well-structured binding sites on other biomolecules. Here we demonstrate the existence of an unexpected interaction mechanism: the two intrinsically disordered human proteins histone H1 and its nuclear chaperone prothymosin-α associate in a complex with picomolar affinity, but fully retain their structural disorder, long-range flexibility and highly dynamic character. On the basis of closely integrated experiments and molecular simulations, we show that the interaction can be explained by the large opposite net charge of the two proteins, without requiring defined binding sites or interactions between specific individual residues. Proteome-wide sequence analysis suggests that this interaction mechanism may be abundant in eukaryotes

Molekulare Charakterisierung muriner Noroviren

Das murine Norovirus ist ein neu entdecktes Mitglied der Familie Caliciviridae. Bislang wurden vier Virusstämme beschrieben und charakterisiert (MNV1-4). In dieser Arbeit wurde erstmals die Prävalenz von MNV bei Labormäusen in Deutschland untersucht. Daraufhin wurden die neu detektierten Virusstämme anhand ihrer morphologischen, phylogenetischen und pathogenen Eigenschaften charakterisiert. In 55% der untersuchten 82 Kotproben wurde mittels real-time PCR die Ausscheidung von MNV nachgewiesen. Morphologische Untersuchungen bestätigten das Vorhandensein intakter Viruspartikel in den Proben, die auch genetisch als MNVs charakterisiert wurden. Phylogenetisch wurden die Viren in vier genetische Cluster eingruppiert, die sich sowohl untereinander als auch von den Stämmen MNV1-4 deutlich unterscheiden. Die Relevanz der Subklassifizierung von MNV wurde durch unterschiedliche Wachstumskinetiken und IFN-beta-Sensitivitäten divergenter Stämme funktional bekräftigt. Zudem konnten, basierend auf Sequenzdaten aus zwei subgenomischen Bereichen, rekombinante Virusstämme identifiziert werden. Durch Kokultivierung von MNV-Isolaten wurde homologe Rekombination von Noroviren erstmals in vitro simuliert. Beobachtungen von natürlich und experimentell infizierten Mäusen zeigten, dass der Stamm MNV-M21 in den Tieren eine persistierende Infektion induziert. Serologische Untersuchungen verdeutlichten, dass die Persistenz unabhängig von einer intakten und protektiven Immunantwort stattfand. Bestimmungen der ORF2-Sequenzen zu unterschiedlichen Zeitpunkten der Infektion gaben Hinweise auf Antigendrift der hypervariablen P2-Domäne. Innerhalb dieser Domäne ist eine zwischen murinen und humanen Noroviren konservierte Proteinsequenz lokalisiert. Die antigenen Eigenschaften dieses Peptids wurden genauer untersucht. Generierte Antiseren zeigten Kreuzreaktivitäten gegenüber verschiedenen Norovirus-Kapsidproteinen. Zudem waren Peptidantikörper in der Lage eine MNV-Infektion in vitro zu neutralisieren.The murine norovirus is a newly discovered member of the familiy Caliciviridae. So far, four strains have been described and characterised (MNV1-4). This is the first study on the prevalence of MNV among laboratory mice in Germany. Thereupon the detected new strains have been characterised considering morphologic, phylogenetic and pathogenic properties. Using real-time PCR, shedding of MNV has been found in 55% of 82 investigated faeces samples. Morphologic investigations confirmed the presence of intact virus particles within the samples, which genetically also have been characterised as MNVs. Phylogenetically these viruses have been grouped into four genetic clusters, which could be distinguished from each other and from strains MNV1-4. Relevance of MNV subtyping has been functionally corroborated through different growth kinetics and Interferon-beta sensitivities of divergent strains. Based on subtyping in two different subgenomic regions, recombinant strains have been identified. By cocultivation of MNV isolates, homologous recombination of noroviruses in vitro has been simulated for the first time. Studies of naturally and experimentally infected mice showed that strain MNV-M21 induce a persistent infection. Serological testings confirmed that the persistence occured independently of an intact and protective immune response. Determination of ORF2 sequences at different time points of infection indicated antigenic drift of the hypervariable P2 domain. A protein sequence stretch, which is conserved between murine and human noroviruses, is located within this domain. The antigenic features of this stretch have been investigated. Generated antisera against this peptide were crossreactive with different norovirus capsid proteins and were able to neutralize MNV infection in vitro

The nuclear pore complex becomes alive: New insights into its dynamics and involvement in different cellular processes

Abstract In this review we summarize the structure and function of the nuclear pore complex (NPC). Special emphasis is put on recent findings which reveal the NPC as a dynamic structure in the context of cellular events like nucleocytoplasmic transport, cell division and differentiation, stress response and apoptosis. Evidence for the involvement of nucleoporins in transcription and oncogenesis is discussed, and evolutionary strategies developed by viruses to cross the nuclear envelope are presented

How Intuitive Is the Administration of Pediatric Emergency Medication Devices for Parents? Objective Observation and Subjective Self-Assessment

Background: to assess the intuitiveness of parents’ administration of pediatric emergency devices (inhalation, rectal, buccal, nasal, and auto-injector). Methods: We invited parents without prior experience to administer the five devices to dummy dolls. We observed whether the parents chose the correct administration route and subsequently performed the correct administration procedures without clinically relevant errors. We interviewed parents for their self-assessment of their own administration performance and willingness to administer devices in actual emergencies. Results: The correct administration route was best for the inhalation device (81/84, 96% of parents) and worst for the intranasal device (25/126, 20%). The correct administration procedures were best for the buccal device (63/98, 64%) and worst for the auto-injector device (0/93, 0%). Their own administration performance was rated to be best by parents for the inhalation device (59/84, 70%) and worst for the auto-injector device (17/93, 18%). The self-assessment of the correct administration overestimated the correct administration procedures for all the devices except the buccal one. Most parents were willing to administer the inhalation device in an emergency (67/94, 79%), while the fewest were willing to administration procedures the auto-injector device (28/93, 30%). Conclusions: Intuitiveness concerning the correct administration route and the subsequent correct administration procedures have to be improved for all the devices examined. The parents mostly overestimated their performance. Willingness to use a device in an actual emergency depended on the device

Active focus stabilization for fluorescence microscopy by tracking actively generated infrared spots

van den Berg B, Van den Eynde R, Müller M, Vandenberg W, Dedecker P. Active focus stabilization for fluorescence microscopy by tracking actively generated infrared spots. bioRxiv. 2020.Maintaining focus during time-lapse experiments remains an important challenge in optical microscopy. In this paper we present an automated focusing system for fluorescence microscopy that can be used in time-lapse experiments. We provide software for flexibly operating the autofocus system and a complete alignment guide. The system is evaluated using a time-lapse experiment with temperature variations on Tetraspeck beads

Febrile seizures: perceptions and knowledge of parents of affected and unaffected children

Febrile seizures (FS) in children are common, but little is known about parents' perceptions and knowledge of FS. We interviewed parents of children aged 6 months to 6 years affected by FS (FS group, 65 parents) or unaffected (control group, 54 parents). In the FS group, 32% said they knew their child had an FS when the first event occurred, and 89% described fear when the child had a seizure, with a median intensity of 10/10 (Q25/Q75: 9/10). Related to follow-up, 77% in the FS group (will) observe their child more carefully after the first seizure happened, and 63% (will) give antipyretics earlier at a median temperature of 38.2 °C (100.8 °F). In the FS group, 62% were unaware of FS before the first event (54% of control group did not know about FS thus far, n.s.). In the FS group, 20% would put a solid object in the mouth of a child having a seizure (control group, 39%, p = 0.030), and 92% would administer an available anti-seizure rescue medication (control group, 78%, p = 0.019). In the FS group, 71% feared that children with FS might suffocate (control group, 70%, n.s.).!##!Conclusion!#!Information about FS and their management should be more available to improve parents' coping and patient safety.!##!What is known!#!• Febrile seizures in children are common. • The prognosis of children suffering from febrile seizures is usually rather good.!##!What is new!#!• Over half of parents had not informed themselves about febrile seizures so far; and only 32% of parents realized their child had a febrile seizure when it occurred. • Most parents described own fear with a median intensity of 10/10; and 63% (will) give antipyretics earlier at a median temperature of 38.2 °C (100.8 °F)