Ribosome biogenesis requires numerous trans-acting factors, some of which are deeply conserved. In Bacteria, the endoribonuclease YbeY is believed to be involved in 16S rRNA 3′-end processing and its loss was associated with ribosomal abnormalities. In Eukarya, YBEY appears to generally localize to mitochondria (or chloroplasts). Here we show that the deletion of human YBEY results in a severe respiratory deficiency and morphologically abnormal mitochondria as an apparent consequence of impaired mitochondrial translation. Reduced stability of 12S rRNA and the deficiency of several proteins of the small ribosomal subunit in YBEY knockout cells pointed towards a defect in mitochondrial ribosome biogenesis. The specific interaction of mitoribosomal protein uS11m with YBEY suggests that the latter helps to properly incorporate uS11m into the nascent small subunit in its late assembly stage. This scenario shows similarities with final stages of cytosolic ribosome biogenesis, and may represent a late checkpoint before the mitoribosome engages in translation.

With global demand for SARS-CoV-2 testing ever rising, shortages in commercially available viral transport media pose a serious problem for laboratories and health care providers. For reliable diagnosis of SARS-CoV-2 and other respiratory viruses, executed by Real-time PCR, the quality of respiratory specimens, predominantly determined by transport and storage conditions, is crucial. Therefore, our aim was to explore the reliability of minimal transport media, comprising saline or the CDC recommended Viral Transport Media (HBSS VTM), for the diagnosis of SARS-CoV-2 and other respiratory viruses (influenza A, respiratory syncytial virus, adenovirus, rhinovirus and human metapneumovirus) compared to commercial products, such as the Universal Transport Media (UTM). We question the assumptions, that the choice of medium and temperature for storage and transport affect the accuracy of viral detection by RT-PCR. Both alternatives to the commercial transport medium (UTM), HBSS VTM or saline, allow adequate detection of SARS-CoV-2 and other respiratory viruses, regardless of storage temperatures up to 28 °C and storage times up to 28 days. Our study revealed the high resilience of SARS-CoV-2 and other respiratory viruses, enabling proper detection in clinical specimens even after long-time storage at high temperatures, independent of the transport medium’s composition.

Ribosome biogenesis requires numerous trans-acting factors, some of which are deeply conserved. In Bacteria, the endoribonuclease YbeY is believed to be involved in 16S rRNA 3'-end processing and its loss was associated with ribosomal abnormalities. In Eukarya, YBEY appears to generally localize to mitochondria (or chloroplasts). Here we show that the deletion of human YBEY results in a severe respiratory deficiency and morphologically abnormal mitochondria as an apparent consequence of impaired mitochondrial translation. Reduced stability of 12S rRNA and the deficiency of several proteins of the small ribosomal subunit in YBEY knockout cells pointed towards a defect in mitochondrial ribosome biogenesis. The specific interaction of mitoribosomal protein uS11m with YBEY suggests that the latter recruits uS11m to the nascent small subunit in its late assembly stage. This scenario shows similarities with final stages of cytosolic ribosome biogenesis, and may represent a late checkpoint before the mitoribosome engages in translation. INTRODUCTIONRibosome biogenesis is a highly complex process that starts co-transcriptionally and includes ribosomal RNA processing, modification, and binding of ribosomal proteins (1). Each of these steps relies on specific factors, some of which are remarkably conserved. One such factor is the UPF0054 family protein YbeY found in all classified bacteria (2). Based on studies in various bacteria, YbeY has been implicated in ribosome maturation and quality control, with a particularly important role in small subunit (SSU) biogenesis (3-8), and post-transcriptional gene expression regulation (9-14). The deletion of ybeY is often lethal or associated with severe alterations of cellular metabolism and growth, indicating its indispensability for a wide variety of bacterial-type ribosomes (4,6,7,(13)(14)(15)(16)(17).Mechanistically, YbeY has been described as a metal-dependent endoribonuclease (5,12), and in some bacteria, ybeY mutants accumulate 16S rRNA with an unprocessed 3' end (3,5,7,8). Therefore, YbeY was proposed to be the "missing" 3' endoribonuclease required for 16S rRNA maturation to obtain the correct anti-Shine-Dalgarno sequence, which is needed for translation initiation on most bacterial mRNAs. However, this 16S rRNA 3'-misprocessing phenotype could equally be caused by the loss of a ribosome biogenesis factor that is not per se involved in rRNA cleavage (18), and so the precise role of YbeY in ribosome biogenesis remains unclear.By carrying out an in-depth phylogenetic analysis, we found that YBEY is also conserved in many eukaryal lineages, including animals, plants, most stramenopiles and alveolates (Supplementary Figure 1). Indeed, YbeY of Arabidopsis thaliana was reported to be an essential ribosome biogenesis factor in chloroplasts, and its absence was associated with severe misprocessing of nearly all chloroplast rRNAs, resulting in deficiency of organellar translation, and hence, the absence of photosynthesis (16). Human YBEY, which shares 27% of identity with YbeY of...

Reliable diagnosis, executed by Real-Time PCR (RT-PCR), builds the current basis in SARS-CoV-2 containment. Transport and storage conditions are the main indicators determining the quality of respiratory specimens. According to shortages in commercially available viral transport media, the primary aim of this study was to explore the reliability of minimal transport media including saline and CDC Viral Transport Media (HBSS VTM) composition for SARS-CoV-2 diagnosis by Real-time PCR compared to recommended commercially available standard Universal Transport Media (UTM). This study also implicated the stability of other respiratory viruses, including influenza A, respiratory syncytial virus, adenovirus, rhinovirus and human metapneumovirus, providing further evidence for future recommendations on transport and storage of respiratory viruses. Both viral transport media (self-made HBSS VTM and UTM) and saline (0.9% NaCl) allow adequate detection of SARS-CoV-2 and other respiratory viruses, regardless of an increase in storage temperature (up to 28 °C) and time (over 28 days). Treatment of SARS-CoV-2 specimens with varying chlorine concentrations, commonly used in swimming pools, resulted in a significant decrease of viral RNA.

During tissue regeneration, mesenchymal stem cells can support endothelial cells in the process of new vessel formation. For a functional interaction of endothelial cells with mesenchymal stem cells a vascular inductive microenvironment is required. Using a cellular model for neo-vessel formation, we could show that newly formed vascular structures emanated from the embedded aggregates, consisting of mesenchymal stem cells co-cultured with autologous human umbilical vein endothelial cells, into avascular human platelet lysate-based matrices, bridging distances up to 5 mm to join with adjacent aggregates with the same morphology forming an interconnected network. These newly formed vascular sprouts showed branch points and generated a lumen, as sign of mature vascular development. In two-dimensional culture, we detected binding of mesenchymal stem cells to laser-damaged endothelial cells under flow conditions, mimicking the dynamics in blood vessels. In conclusion, we observed that mesenchymal stem cells can support human umbilical vein endothelial cells in their vitality and functionality. In xeno-free human platelet lysate-based matrices, endothelial cells form complex vascular networks in a primarily avascular scaffold with the aid of mesenchymal stem cells, when co-cultured in three-dimensional spherical aggregates. Under dynamic conditions, representing the flow rate of venous vessel, mesenchymal stem cells preferably bind to damaged endothelial cells presumably assisting in the healing process.