Adolescent Reference Values for MR-Derived Biventricular Strain Obtained Using Feature-Tracking and Myocardial Tagging.

BACKGROUND: Myocardial strain is a promising marker for the detection of early left or right ventricular (LV or RV) dysfunction in pediatric populations. The reference standard for MR strain measurement is myocardial tagging (MT); however, MT has limited clinical utility because the additional acquisitions needed are time-consuming. In contrast, MR-feature tracking (FT) allows strain quantification from routinely acquired cine sequences. Studies providing reference values obtained with both FT and MT for adolescents are lacking. PURPOSE: To use MR-FT and MT to define sex-specific LV and RV strain reference values for adolescents. STUDY TYPE: Cross-sectional, prospective. POPULATION: One hundred twenty-three adolescents aged 15-18 years (52% girls) without known cardiovascular disease. FIELD STRENGTH/SEQUENCE: Balanced steady-state free-precession sequence for FT analysis and a spatial modulation of magnetization hybrid TFE-EPI sequence for MT acquisitions at 3.0-T. ASSESSMENT: Segment Medviso software was used to obtain longitudinal (LS) and circumferential (CS) strain for both ventricles, and radial strain (RS) for LV. STATISTICAL TESTS: The Student t-test was used for between-sex comparisons of continuous variables. Sex-specific percentiles were calculated using the weighted average method. Intraobserver and interobserver agreement was assessed in 30 randomly selected studies using intraclass correlation coefficients (ICC). A P-value <0.05 was considered statistically significant. RESULTS: FT-derived LVLS and LVCS were significantly higher in girls than in boys (-19.8% vs. -17.8% and -22.2% vs. -21.0%, respectively), as they were with MT (LVLS: -18.1% vs. -16.8%; LVCS: -20.8% vs. -19.7%). FT-LVRS was higher in girls than in boys (44.8% vs. 35.1%), while MT-LVRS was the opposite (18.6% vs. 22.7%). FT-RVLS was higher in girls (-23.4% vs. -21.3%), but there were no between-sex differences in MT-derived RVLS or RVCS. ICC values for intraobserver agreement were ≥0.89, whereas for interobserver agreement were <0.80 for MT-LVRS and ≥0.80 for all remaining parameters. DATA CONCLUSION: This study provides sex-specific reference biventricular strain values obtained with MR-MT and MR-FT for adolescents aged 15-18 years. MR-FT may be a valid method for obtaining strain values in pediatric populations. EVIDENCE LEVEL: 1 TECHNICAL EFFICACY: Stage 3.

Absence of Myocardial Involvement After SARS-CoV-2 Vaccination in Asymptomatic Adolescents.

This study aimed to evaluate the presence of subclinical myocardial damage in adolescents who were vaccinated against SARS-CoV-2. One hundred twenty asymptomatic adolescents with a mean age of 16.0 ± 0.4 years (51% girls) underwent cardiac magnetic resonance (CMR) imaging. SARS-CoV-2 IgG/IgM antibody testing was performed, and self-reported dates of confirmed SARS-CoV-2 infection and/or vaccination were collected. Participants were classified according to SARS-CoV-2 status as naïve (non-infected and unvaccinated, n = 74), infected (unvaccinated, n = 23), and vaccinated (independently of past infection status, n = 23). Biventricular volumes and ejection fraction and myocardial T2 relaxation time were similar in the three groups. T1 relaxation time was slightly higher in vaccinated adolescents (1249 ± 35 ms) than in naïve and infected participants (1231 ± 30 ms and 1227 ± 29 ms, respectively; p = 0.035), although this difference was considered clinically irrelevant. This observational study found no evidence of relevant subclinical myocardial involvement after SARS-CoV-2 vaccination in asymptomatic adolescents.

Angina en pacientes con estenosis aórtica grave sometidos a implante percutáneo de la válvula aórtica / Angina in patients with severe aortic stenosis undergoing transcatheter aortic valve replacement

Introducción y objetivos: Evaluar la prevalencia, las características clínicas y el impacto de la angina en pacientes con estenosis aórtica sometidos a implante percutáneo de válvula aórtica (TAVI). Métodos: Se analizó a 1.687 pacientes consecutivos con estenosis aórtica sometidos a TAVI, clasificados en función de la presencia o ausencia basal de angina. Los datos basales, del procedimiento y del seguimiento se recogieron en una base de datos local. Resultados: Un total de 497 pacientes (29%) presentaban angina antes del TAVI. Los pacientes con angina basal presentaban peor clase funcional (NYHA> II, el 69% frente al 63%; p=0,017) y una mayor prevalencia de enfermedad coronaria (el 74% frente al 56%; p <0,001). La angina basal no mostró impacto pronóstico a 1 año en mortalidad por cualquier causa (HR=1,02; IC95%, 0,71-1,48; p=0,898) ni en mortalidad cardiovascular (HR=1,2; IC95%, 0,69-2,11; p=0,517). Sin embargo, la persistencia de angina 30 días después del procedimiento se asoció con un incremento en la mortalidad a 1 año, tanto total (HR=4,86; IC95%, 1,71-13,8; p=0,003) como de causa cardiovascular (HR=20,7; IC95%, 3,50-122,6; p=0,001). Conclusiones: Más de un cuarto de los pacientes con estenosis aórtica sometidos a TAVI tenían angina antes del procedimiento. La angina basal no mostró impacto pronóstico alguno. Sin embargo, la persistencia de angina 30 días después del procedimiento se asoció con una mayor mortalidad al año.(AU)

Introduction and objectives: To evaluate the prevalence, clinical characteristics, and outcomes of patients with angina undergoing transcatheter aortic valve replacement (TAVR) for severe aortic stenosis. Methods: A total of 1687 consecutive patients with severe aortic stenosis undergoing TAVR at our center were included and classified according to patient-reported angina symptoms prior to the TAVR procedure. Baseline, procedural and follow-up data were collected in a dedicated database. Results: A total of 497 patients (29%) had angina prior to the TAVR procedure. Patients with angina at baseline showed a worse New York Heart Association (NYHA) functional class (NYHA class> II: 69% vs 63%; P=.017), a higher rate of coronary artery disease (74% vs 56%; P <.001), and a lower rate of complete revascularization (70% vs 79%; P <.001). Angina at baseline had no impact on all-cause mortality (HR, 1.02; 95%CI, 0.71-1.48; P=.898) and cardiovascular mortality (HR, 1.2; 95%CI, 0.69-2.11; P=.517) at 1 year. However, persistent angina at 30 days post-TAVR was associated with increased all-cause mortality (HR, 4.86; 95%CI, 1.71-13.8; P=.003) and cardiovascular mortality (HR, 20.7; 95%CI, 3.50-122.6; P=.001) at 1-year follow-up. Conclusions: More than one-fourth of patients with severe aortic stenosis undergoing TAVR had angina prior to the procedure. Angina at baseline did not appear to be a sign of a more advanced valvular disease and had no prognostic impact; however, persistent angina at 30 days post-TAVR was associated with worse clinical outcomes.(AU)

Structure-function relationships in protein homorepeats.

Homorepeats (or polyX), protein segments containing repetitions of the same amino acid, are abundant in proteomes from all kingdoms of life and are involved in crucial biological functions as well as several neurodegenerative and developmental diseases. Mainly inserted in disordered segments of proteins, the structure/function relationships of homorepeats remain largely unexplored. In this review, we summarize present knowledge for the most abundant homorepeats, highlighting the role of the inherent structure and the conformational influence exerted by their flanking regions. Recent experimental and computational methods enable residue-specific investigations of these regions and promise novel structural and dynamic information for this elusive group of proteins. This information should increase our knowledge about the structural bases of phenomena such as liquid-liquid phase separation and trinucleotide repeat disorders.

A cyclin-dependent kinase-mediated phosphorylation switch of disordered protein condensation.

Cell cycle transitions result from global changes in protein phosphorylation states triggered by cyclin-dependent kinases (CDKs). To understand how this complexity produces an ordered and rapid cellular reorganisation, we generated a high-resolution map of changing phosphosites throughout unperturbed early cell cycles in single Xenopus embryos, derived the emergent principles through systems biology analysis, and tested them by biophysical modelling and biochemical experiments. We found that most dynamic phosphosites share two key characteristics: they occur on highly disordered proteins that localise to membraneless organelles, and are CDK targets. Furthermore, CDK-mediated multisite phosphorylation can switch homotypic interactions of such proteins between favourable and inhibitory modes for biomolecular condensate formation. These results provide insight into the molecular mechanisms and kinetics of mitotic cellular reorganisation.

Incidence, Predictors, and Prognostic Impact of Bleeding Events After TAVR According to VARC-3 Criteria.

BACKGROUND: The updated Valve Academic Research Consortium (VARC) definition for bleeding events after transcatheter aortic valve replacement (TAVR) lacks of clinical validation. OBJECTIVES: The aim of this study was to determine the incidence, predictors, and clinical impact of bleeding events following TAVR as defined by recent VARC-3 criteria. METHODS: A total of 2,384 consecutive patients with severe symptomatic aortic stenosis undergoing TAVR were included. Early (at index hospitalization) and late (after hospital discharge) bleeding complications were defined according to VARC-3 criteria as type 1, 2, 3, or 4. Baseline, procedural, and follow-up (24 [IQR: 12-43] months) data were prospectively collected. RESULTS: Bleeding events occurred in 761 patients (31.9%): types 1, 2, 3, and 4 in 169 (22.2%), 399 (52.4%), 149 (19.6%), and 44 (5.8%) patients, respectively. The primary vascular access site and gastrointestinal locations were the most common bleeding sources among early and late bleeding events, respectively. Female sex, thoracotomy access, larger (14-F) sheath use, and dual antiplatelet therapy determined an increased risk of early bleeding events (P < 0.02 for all). The use of the radial artery for secondary access was associated with a significant risk reduction of early bleeding (P < 0.001). Type 2 and type 3 events were associated with an increased mortality risk at 30-day (HR: 2.94 [95% CI: 1.43-6.03; P = 0.003] and HR: 4.91 [95% CI: 2.19-11.03; P < 0.001], respectively) and 1-year (HR: 1.86 [95% CI: 1.28-2.69; P = 0.001] and HR: 2.28 [95% CI: 1.41-3.66; P = 0.001], respectively) follow-up. A similar prognostic pattern was observed when applying VARC-2 criteria but with a much lower global incidence of early bleeding events (19% vs 27%; P < 0.001). CONCLUSIONS: Bleeding events after TAVR were associated with poorer short- and long-term survival. The magnitude of this correlation was proportional to bleeding severity defined according to VARC-3 criteria. Further studies on bleeding prevention following TAVR are warranted to improve procedural safety and patient prognosis.

Site-Specific Introduction of Alanines for the Nuclear Magnetic Resonance Investigation of Low-Complexity Regions and Large Biomolecular Assemblies.

Nuclear magnetic resonance (NMR) studies of large biomolecular machines and highly repetitive proteins remain challenging due to the difficulty of assigning frequencies to individual nuclei. Here, we present an efficient strategy to address this challenge by engineering a Pyrococcus horikoshii tRNA/alanyl-tRNA synthetase pair that enables the incorporation of up to three isotopically labeled alanine residues in a site-specific manner using in vitro protein expression. The general applicability of this approach for NMR assignment has been demonstrated by introducing isotopically labeled alanines into four distinct proteins: huntingtin exon-1, HMA8 ATPase, the 300 kDa molecular chaperone ClpP, and the alanine-rich Phox2B transcription factor. For large protein assemblies, our labeling approach enabled unambiguous assignments while avoiding potential artifacts induced by site-specific mutations. When applied to Phox2B, which contains two poly-alanine tracts of nine and twenty alanines, we observed that the helical stability is strongly dependent on the homorepeat length. The capacity to selectively introduce alanines with distinct labeling patterns is a powerful tool to probe structure and dynamics of challenging biomolecular systems.

Angina in patients with severe aortic stenosis undergoing transcatheter aortic valve replacement.

INTRODUCTION AND OBJECTIVES: To evaluate the prevalence, clinical characteristics, and outcomes of patients with angina undergoing transcatheter aortic valve replacement (TAVR) for severe aortic stenosis. METHODS: A total of 1687 consecutive patients with severe aortic stenosis undergoing TAVR at our center were included and classified according to patient-reported angina symptoms prior to the TAVR procedure. Baseline, procedural and follow-up data were collected in a dedicated database. RESULTS: A total of 497 patients (29%) had angina prior to the TAVR procedure. Patients with angina at baseline showed a worse New York Heart Association (NYHA) functional class (NYHA class> II: 69% vs 63%; P=.017), a higher rate of coronary artery disease (74% vs 56%; P <.001), and a lower rate of complete revascularization (70% vs 79%; P <.001). Angina at baseline had no impact on all-cause mortality (HR, 1.02; 95%CI, 0.71-1.48; P=.898) and cardiovascular mortality (HR, 1.2; 95%CI, 0.69-2.11; P=.517) at 1 year. However, persistent angina at 30 days post-TAVR was associated with increased all-cause mortality (HR, 4.86; 95%CI, 1.71-13.8; P=.003) and cardiovascular mortality (HR, 20.7; 95%CI, 3.50-122.6; P=.001) at 1-year follow-up. CONCLUSIONS: More than one-fourth of patients with severe aortic stenosis undergoing TAVR had angina prior to the procedure. Angina at baseline did not appear to be a sign of a more advanced valvular disease and had no prognostic impact; however, persistent angina at 30 days post-TAVR was associated with worse clinical outcomes.

Myocardial Injury After Transcatheter Aortic Valve Replacement According to VARC-3 Criteria.

BACKGROUND: The Valve Academic Research Consortium (VARC)-3 definition for myocardial injury after transcatheter aortic valve replacement (TAVR) lacks of clinical validation. OBJECTIVES: This study sought to determine the incidence, predictors, and clinical impact of periprocedural myocardial injury (PPMI) following TAVR as defined by recent VARC-3 criteria. METHODS: We included 1,394 consecutive patients who underwent TAVR with a new-generation transcatheter heart valve. High-sensitivity troponin levels were assessed at baseline and within 24 hours after the procedure. PPMI was defined according to VARC-3 criteria as an increase ≥70 times in troponin levels (vs ≥15 times according to the VARC-2 definition). Baseline, procedural, and follow-up data were prospectively collected. RESULTS: PPMI was diagnosed in 193 (14.0%) patients. Female sex and peripheral artery disease were independent predictors of PPMI (P < 0.01 for both). PPMI was associated with a higher risk of mortality at 30-day (HR: 2.69, 95% CI: 1.50-4.82; P = 0.001) and 1-year (for all-cause mortality, HR: 1.54; 95% CI: 1.04-2.27; P = 0.032; for cardiovascular mortality, HR: 3.04; 95% CI: 1.68-5.50; P < 0.001) follow-up. PPMI according to VARC-2 criteria had no impact on mortality. CONCLUSIONS: About 1 out of 10 patients undergoing TAVR in the contemporary era had PPMI as defined by recent VARC-3 criteria, and baseline factors like female sex and peripheral artery disease determined an increased risk. PPMI had a negative impact on early and late survival. Further studies on the prevention of PPMI post-TAVR and implementing measures to improve outcomes in PPMI patients are warranted.

Multi-site-specific isotopic labeling accelerates high-resolution structural investigations of pathogenic huntingtin exon-1.

Huntington's disease neurodegeneration occurs when the number of consecutive glutamines in the huntingtin exon-1 (HTTExon1) exceeds a pathological threshold of 35. The sequence homogeneity of HTTExon1 reduces the signal dispersion in NMR spectra, hampering its structural characterization. By simultaneously introducing three isotopically labeled glutamines in a site-specific manner in multiple concatenated samples, 18 glutamines of a pathogenic HTTExon1 with 36 glutamines were unambiguously assigned. Chemical shift analyses indicate the α-helical persistence in the homorepeat and the absence of an emerging toxic conformation around the pathological threshold. Using the same type of samples, the recognition mechanism of Hsc70 molecular chaperone has been investigated, indicating that it binds to the N17 region of HTTExon1, inducing the partial unfolding of the poly-Q. The proposed strategy facilitates high-resolution structural and functional studies in low-complexity regions.

Influence of the storage procedure on the trace element content measured in the aquatic moss Fontinalis antipyretica Hedw.

Aquatic bryophytes have been used as pollution biomonitors for decades. Despite this, sample collection and preparation methods have not been standardized, which makes it difficult to compare the results of different studies. Most times, the samples have to be stored before processing, for example, when many of them are collected in a short time, as occurs in extensive pollution studies. Storage must be done in a way that does not change the pollutant concentrations in the samples. We studied whether the concentrations of Al, As, Ba, Cd, Cr, Cu, Fe, Hg, Mn, Ni, Pb, and Zn in the aquatic moss Fontinalis antipyretica were affected by three storage procedures: dry at room temperature, fresh (in refrigerator at 6°C), and frozen at -20°C. In addition, we evaluated whether the subsequent washing of the samples affected the concentrations of these elements differently depending on the storage method. Our results showed that the three methods were, in general, adequate since the concentrations did not change, and we did not observe differences between washed and unwashed samples either. Since the simplest method is refrigeration, we concluded that this is the best of them. However, the concentrations of Hg increased steadily over time in the fresh material, probably because of redistribution after volatilization from the basal parts of the mosses. We believe that the respiration of the plants lowered the concentrations of oxygen inside the hermetically sealed bags containing the samples, thus promoting the reduction of the Hg and its posterior volatilization and redistribution. We did not observe interactions between the storage method and the posterior washing of the samples. PRACTITIONER POINTS: We studied the influence of storage procedure on element content in aquatic mosses. The procedures were as follows: dried at room temperature, stored in refrigerator, and frozen. The procedures did not change the element contents, except for Hg in refrigerator. All the procedures seemed suitable, but refrigeration was the simplest one.

Magnetic resonance imaging reference values for cardiac morphology, function and tissue composition in adolescents.

Background: Cardiovascular magnetic resonance (CMR) is a precise tool for the assessment of cardiac anatomy, function, and tissue composition. However, studies providing CMR reference values in adolescence are scarce. We aim to provide sex-specific CMR reference values for biventricular and atrial dimensions and function and myocardial relaxation times in this population. Methods: Adolescents aged 15-18 years with no known cardiovascular disease underwent a non-contrast 3-T CMR scan between March 2021 and October 2021. The imaging protocol included a cine steady-state free-precession sequence for the analysis of chamber size and function, as well as T2-GraSE and native MOLLI T1-mapping for the characterization of myocardial tissue. Findings: CMR scans were performed in 123 adolescents (mean age 16 ± 0.5 years, 52% girls). Mean left and right ventricular end-diastolic indexed volumes were higher in boys than in girls (91.7 ± 11.6 vs 78.1 ± 8.3 ml/m2, p < 0.001; and 101.3 ± 14.1 vs 84.1 ± 10.5 ml/m2, p < 0.001), as was the indexed left ventricular mass (48.5 ± 9.6 vs 36.6 ± 6.0 g/m2, p < 0.001). Left ventricular ejection fraction showed no significant difference by sex (62.2 ± 4.1 vs 62.8 ± 4.2%, p = 0.412), whereas right ventricular ejection fraction trended slightly lower in boys (55.4 ± 4.7 vs. 56.8 ± 4.4%, p = 0.085). Indexed atrial size and function parameters did not differ significantly between sexes. Global myocardial native T1 relaxation time was lower in boys than in girls (1215 ± 23 vs 1252 ± 28 ms, p < 0.001), whereas global myocardial T2 relaxation time did not differ by sex (44.4 ± 2.0 vs 44.1 ± 2.4 ms, p = 0.384). Sex-stratified comprehensive percentile tables are provided for most relevant cardiac parameters. Interpretation: This cross-sectional study provides overall and sex-stratified CMR reference values for cardiac dimensions and function, and myocardial tissue properties, in adolescents. This information is useful for clinical practice and may help in the differential diagnosis of cardiac diseases, such as cardiomyopathies and myocarditis, in this population. Funding: Instituto de Salud Carlos III (PI19/01704).

The structure of pathogenic huntingtin exon 1 defines the bases of its aggregation propensity.

Huntington's disease is a neurodegenerative disorder caused by a CAG expansion in the first exon of the HTT gene, resulting in an extended polyglutamine (poly-Q) tract in huntingtin (httex1). The structural changes occurring to the poly-Q when increasing its length remain poorly understood due to its intrinsic flexibility and the strong compositional bias. The systematic application of site-specific isotopic labeling has enabled residue-specific NMR investigations of the poly-Q tract of pathogenic httex1 variants with 46 and 66 consecutive glutamines. Integrative data analysis reveals that the poly-Q tract adopts long α-helical conformations propagated and stabilized by glutamine side chain to backbone hydrogen bonds. We show that α-helical stability is a stronger signature in defining aggregation kinetics and the structure of the resulting fibrils than the number of glutamines. Our observations provide a structural perspective of the pathogenicity of expanded httex1 and pave the way to a deeper understanding of poly-Q-related diseases.

El electrocardiograma en la amiloidosis cardíaca: un arma para la sospecha diagnóstica de esta enfermedad / The electrocardiogram in cardiac amyloidosis: a weapon for the diagnosis suspect of this disease / O electrocardiograma na amiloidose cardíaca: uma arma para a suspeita diagnóstica desta doença

La amiloidosis cardíaca (AC) es una enfermedad con mal pronóstico si el tratamiento no se inicia de forma temprana, por lo que una de las asignaturas pendientes en esta enfermedad consiste en realizar un diagnóstico precoz. El electrocardiograma (ECG) es una prueba diagnóstica de bajo costo y amplia disponibilidad que nos permite sospechar esta enfermedad, dado que resulta normal en < 5% de los pacientes. El hallazgo clásico es la presencia de bajos voltajes en relación con la gran hipertrofia que se observa en las pruebas de imagen, así como el conocido patrón de pseudoinfarto. Ambos hallazgos son más frecuentes en el subtipo de amiloidosis por cadenas ligeras, que era el más frecuentemente diagnosticado en el pasado. Sin embargo, con la expansión del diagnóstico no invasivo del subtipo a transtiretina, su identificación ha crecido de forma exponencial y se convirtió en el más diagnosticado con más frecuencia en nuestro medio. Se debe prestar especial atención a todos estos hallazgos electrocardiográficos, con el fin de que esta prueba diagnóstica de sencilla obtención pueda contribuir de forma importante a la sospecha y al diagnóstico precoz de la AC.

Cardiac amyloidosis (CA) is a serious disease with a poor prognosis if treatment is not started early, so one of the pending issues in this condition is to make an early diagnosis. The electrocardiogram (EKG) is an inexpensive and widely available diagnostic test that can offer differential data when suspecting this disease, being normal in < 5% of these patients. The classic EKG finding is the presence of low voltages in relation to the large hypertrophy seen on imaging tests, as well as the well-known pseudoinfarct pattern. Both findings are more frequent in the light chain subtype of CA, which was the most frequently diagnosed in the past. However, with the growth of noninvasive diagnostic tests, the identification of the transtyretin subtype has grown exponentially, becoming the most frequently diagnosed in our setting. Special attention should be paid to all these electrocardiographic findings, so that this simple diagnostic test can make an important contribution to the early suspicion and diagnosis of CA.

A amiloidose cardíaca (AC) é uma doença grave com um mau prognóstico no caso de não se iniciar tratamento de forma precoce, pelo que a necessidade de um pronto diagnóstico é imperiosa. Quando se suspeita desta doença, o eletrocardiograma (ECG) é um teste de diagnóstico pouco dispendioso e disponível em todo o mundo, que pode fornecer dados discriminativos importantes, sendo normal em menos de 5% dos casos. O achado clássico do ECG é a presença de baixas voltagens em relação à grande hipertrofia vista na imagem, bem como o conhecido padrão de pseudoinfarte. Ambos os resultados são mais frequentes no subtipo a cadenas ligeras, o mais frequentemente diagnosticado no passado. No entanto, com o aumento dos testes de diagnóstico não-invasivos, o diagnóstico ddo subtipo a transtirretina, o mais cresceu de forma exponencial, tornando-se o mais frequentemente diagnosticado no nosso meio. Deve ser dada especial atenção a todos estes achados eletrocardiográficos já que esta prova de diagnóstico de fácil obtenção pode contribuir de forma importante para a suspeição de diagnóstico precoce de AC.

Nucleus-translocated mitochondrial cytochrome c liberates nucleophosmin-sequestered ARF tumor suppressor by changing nucleolar liquid-liquid phase separation.

The regular functioning of the nucleolus and nucleus-mitochondria crosstalk are considered unrelated processes, yet cytochrome c (Cc) migrates to the nucleus and even the nucleolus under stress conditions. Nucleolar liquid-liquid phase separation usually serves the cell as a fast, smart mechanism to control the spatial localization and trafficking of nuclear proteins. Actually, the alternative reading frame (ARF), a tumor suppressor protein sequestered by nucleophosmin (NPM) in the nucleoli, is shifted out from NPM upon DNA damage. DNA damage also triggers early translocation of respiratory Cc to nucleus before cytoplasmic caspase activation. Here, we show that Cc can bind to nucleolar NPM by triggering an extended-to-compact conformational change, driving ARF release. Such a NPM-Cc nucleolar interaction can be extended to a general mechanism for DNA damage in which the lysine-rich regions of Cc-rather than the canonical, arginine-rich stretches of membrane-less organelle components-controls the trafficking and availability of nucleolar proteins.

The sequence context in poly-alanine regions: structure, function and conservation.

MOTIVATION: Poly-alanine (polyA) regions are protein stretches mostly composed of alanines. Despite their abundance in eukaryotic proteomes and their association to nine inherited human diseases, the structural and functional roles exerted by polyA stretches remain poorly understood. In this work we study how the amino acid context in which polyA regions are settled in proteins influences their structure and function. RESULTS: We identified glycine and proline as the most abundant amino acids within polyA and in the flanking regions of polyA tracts, in human proteins as well as in 17 additional eukaryotic species. Our analyses indicate that the non-structuring nature of these two amino acids influences the α-helical conformations predicted for polyA, suggesting a relevant role in reducing the inherent aggregation propensity of long polyA. Then, we show how polyA position in protein N-termini relates with their function as transit peptides. PolyA placed just after the initial methionine is often predicted as part of mitochondrial transit peptides, whereas when placed in downstream positions, polyA are part of signal peptides. A few examples from known structures suggest that short polyA can emerge by alanine substitutions in α-helices; but evolution by insertion is observed for longer polyA. Our results showcase the importance of studying the sequence context of homorepeats as a mechanism to shape their structure-function relationships. AVAILABILITY AND IMPLEMENTATION: The datasets used and/or analyzed during the current study are available from the corresponding author onreasonable request. SUPPLEMENTARY INFORMATION: Supplementary data are available at Bioinformatics online.