The Arabidopsis SR45 splicing factor bridges the splicing machinery and the exon-exon junction complex.

The Arabidopsis splicing factor serine/arginine-rich 45 (SR45) contributes to several biological processes. The sr45-1 loss-of-function mutant exhibits delayed root development, late flowering, unusual numbers of floral organs, shorter siliques with decreased seed sets, narrower leaves and petals, and altered metal distribution. SR45 bears a unique RNA recognition motif (RRM) flanked by one serine/arginine-rich (RS) domain on both sides. Here, we studied the function of each SR45 domains by examining their involvement in: (i) the spatial distribution of SR45; (ii) the establishment of a protein-protein interaction network including spliceosomal and exon-exon junction complex (EJC) components; and (iii) the RNA binding specificity. We report that the endogenous SR45 promoter is active during vegetative and reproductive growth, and that the SR45 protein localizes in the nucleus. We demonstrate that the C-terminal arginine/serine-rich domain is a determinant of nuclear localization. We show that the SR45 RRM domain specifically binds purine-rich RNA motifs via three residues (H101, H141, and Y143), and is also involved in protein-protein interactions. We further show that SR45 bridges both mRNA splicing and surveillance machineries as a partner of EJC core components and peripheral factors, which requires phosphoresidues probably phosphorylated by kinases from both the CLK and SRPK families. Our findings provide insights into the contribution of each SR45 domain to both spliceosome and EJC assemblies.

The Importance of RSV Epidemiological Surveillance: A Multicenter Observational Study of RSV Infection during the COVID-19 Pandemic.

The restrictive measures adopted worldwide against SARS-CoV-2 produced a drastic reduction in respiratory pathogens, including RSV, but a dramatic rebound was thereafter reported. In this multicenter retrospective observational study in 15 Pediatric Emergency Departments, all children <3 years old with RSV infection admitted between 1 September and 31 December 2021 were included and compared to those admitted in the same period of 2020 and 2019. The primary aim was to evaluate RSV epidemiology during and after the COVID-19 pandemic peak. The secondary aims were to evaluate the clinical features of children with RSV infection. Overall, 1015 children were enrolled: 100 in 2019, 3 in 2020 and 912 in 2021. In 2019, the peak was recorded in December, and in 2021, it was recorded in November. Comparing 2019 to 2021, in 2021 the median age was significantly higher and the age group 2-3 years was more affected. Admissions were significantly higher in 2021 than in 2020 and 2019, and the per-year hospitalization rate was lower in 2021 (84% vs. 93% in 2019), while the duration of admissions was similar. No difference was found in severity between 2019-2020-2021. In conclusion, after the COVID-19 pandemic, an increase in RSV cases in 2021 exceeding the median seasonal peak was detected, with the involvement of older children, while no difference was found in severity.

Weaning in neurally adjusted ventilatory assist: a prospective interventional study in neonates.

BACKGROUND: Neurally adjusted ventilatory assist (NAVA) is a respiratory support triggered by the electrical activity of the diaphragm (EAdi). Only few studies evaluated NAVA short-term efficacy and safety in newborns. Aim of this study was to assess efficacy and safety of NAVA in a cohort of newborns and to analyze ventilation parameters helpful to guide weaning. METHODS: Thirty-four newborns with respiratory failure were ventilated with synchronized intermittent mandatory ventilation plus pressure-regulated volume control plus pressure support (SIMV(PRVC)+PS) for 12 hours and switched to NAVA until extubation. Ventilator and vital parameters, oxygen saturation (SpO2)/fraction of inspired oxygen (FiO2) ratio (S/F), arterialized capillary blood gases (aCBG), and sedatives dose were recorded. The occurrence of reintubation within the first 72 hours, pneumothorax and mortality were evaluated. RESULTS: After 6 hours of NAVA, a significant reduction of FiO2 (0.25 versus 0.32), and peak inspiratory pressure (13 versus 18 mmHg), and a significant increase of S/F (383 versus 316) were found, compared to SIMV(PRVC)+PS. Other ventilation, vital and aCBG parameters were similar in both ventilation modes. During NAVA a significant reduction of sedation was shown. All subjects were successfully extubated guided by EAdi peak during weaning. No reintubation, pneumothorax, or death were recorded. CONCLUSIONS: NAVA can be effectively and safely used in neonates. The EAdi peak could be a reliable index to guide the physicians during weaning and extubation.

Exploring the suitability of RanBP2-type Zinc Fingers for RNA-binding protein design.

Transcriptomes consist of several classes of RNA that have wide-ranging but often poorly described functions and the deregulation of which leads to numerous diseases. Engineering of functionalized RNA-binding proteins (RBPs) could therefore have many applications. Our previous studies suggested that the RanBP2-type Zinc Finger (ZF) domain is a suitable scaffold to investigate the design of single-stranded RBPs. In the present work, we have analyzed the natural sequence specificity of various members of the RanBP2-type ZF family and characterized the interaction with their target RNA. Surprisingly, our data showed that natural RanBP2-type ZFs with different RNA-binding residues exhibit a similar sequence specificity and therefore no simple recognition code can be established. Despite this finding, different discriminative abilities were observed within the family. In addition, in order to target a long RNA sequence and therefore gain in specificity, we generated a 6-ZF array by combining ZFs from the RanBP2-type family but also from different families, in an effort to achieve a wider target sequence repertoire. We showed that this chimeric protein recognizes its target sequence (20 nucleotides), both in vitro and in living cells. Altogether, our results indicate that the use of ZFs in RBP design remains attractive even though engineering of specificity changes is challenging.

Engineering RNA-Binding Proteins by Modular Assembly of RanBP2-Type Zinc Fingers.

Deciphering the function of the nonprotein-coding portion of genomes represents one of the major challenges that molecular biology is facing today. Numerous classes of RNAs have been discovered over the last past decade and appear to play important regulatory roles in gene expression and disease. The ability to study and manipulate these RNAs relies on the development of programmable RNA-binding molecules such as RNA-binding proteins. Most RNA-binding proteins have modular architectures and combine different RNA-binding domains that provide binding affinity toward a specific RNA sequence and/or structure. Herein, we describe a general strategy to design single-stranded RNA-binding proteins using RanBP2-type zinc-finger (ZF) domains that can recognize a given RNA sequence with high affinity and specificity.

Comparison of neurally-adjusted ventilator assist in infants before and after extubation.

BACKGROUND: To compare invasive (iNAVA) and non-invasive (nivNAVA) neurally adjusted ventilatory assist in infants, respect to gas exchange, breathing pattern, respiratory drive, infant-ventilator interaction and synchrony, vital parameters and required sedation. METHODS: Ten consecutive intubated term infants admitted for respiratory failure of different etiology underwent to 2-hour not-randomized trials of iNAVA and, after extubation, nivNAVA, the latter with unchanged ventilator settings and with air-leaks compensating software. Arterialized capillary blood was sampled at the end of each trial. We computed: 1) the minimum (EAdimin) and peak (EAdipeak) values of the diaphragm electrical activity; 2) ventilator (RRmec) and own patients' (RRneu) respiratory rates; 3) inspiratory (delayTR-insp) and expiratory trigger delays (delayTR-exp) and the time of synchrony between patient's effort and ventilator assistance (Timesynch/Tineu); 4) the asynchrony index. Vital parameters and required sedation were also recorded. RESULTS: iNAVA and nivNAVA did not differ between in terms of gas exchange (pH (7.35 [7.31-7.41] vs. 7.36 [7.30-7.40], P=0.745), PcCO2 (38.4 [34.8-42.6] vs. 36.9 [33.9-41.6] mmHg, P=0.469) and PcO2/FiO2 (211 [168-323] vs. 214 [189-282], P=0.195), respectively). EAdimin, EAdipeak, RRmec and RRneu were similar before and after extubation. Both modes confirmed an optimal infant-ventilator interaction (i.e. delayTR-insp, delayTR-exp and Timesynch/Tineu), irrespective of the interface, and no patients showed clinical relevant asynchronies. A low requirement of sedation with fentanyl was recorded during both trials, without differences between. CONCLUSIONS: We found iNAVA and nivNAVA to be characterized by similar gas exchange, breathing pattern, respiratory drive, infant-ventilator interaction and synchrony, vital parameters and required sedation.