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Heterochromatin protein 1 (HP1) is a multifunctional chromatin-associated protein conserved from fission yeast to mammals. HP1 has been suggested to drive heterochromatin formation via phase separation. However, there is seemingly conflicting evidence about HP1 phase-separating in different systems or not. Here, we assess the phase separation behavior of HP1 from fission yeast, fruit fly and mouse in vitro and in mammalian cells side-by-side. We find that HP1 from fission yeast and fly can undergo liquid-liquid phase separation and induce heterochromatin coalescence in mouse cells, in stark contrast to HP1 from mouse. Induced heterochromatin coalescence has only mild effects on gene expression. We link the decreasing phase separation propensity of HP1 homologs to their decreasing intrinsic disorder and their increasing sensitivity to HP1 paralogs antagonizing phase separation. Our work elucidates the relationship between phase separation, nuclear organization and gene expression, and highlights the evolutionary dimension of protein phase separation control. Here, the authors compare HP1 from fission yeast, fly and mouse, and find that the propensity of HP1 to phase-separate and to cluster heterochromatin decrease in this order, suggesting an evolutionary adaptation of HP1 function.

Most transcriptional activity of exponentially growing cells is carried out by the RNA Polymerase I (Pol I), which produces a ribosomal RNA (rRNA) precursor. In budding yeast, Pol I is a multimeric enzyme with 14 subunits. Among them, Rpa49 forms with Rpa34 a Pol I-specific heterodimer (homologous to PAF53/CAST heterodimer in human Pol I), which might be responsible for the specific functions of the Pol I. Previous studies provided insight in the involvement of Rpa49 in initiation, elongation, docking and releasing of Rrn3, an essential Pol I transcription factor. Here, we took advantage of the spontaneous occurrence of extragenic suppressors of the growth defect of the rpa49 null mutant to better understand the activity of Pol I. Combining genetic approaches, biochemical analysis of rRNA synthesis and investigation of the transcription rate at the individual gene scale, we characterized mutated residues of the Pol I as novel extragenic suppressors of the growth defect caused by the absence of Rpa49. When mapped on the Pol I structure, most of these mutations cluster within the jaw-lobe module, at an interface formed by the lobe in Rpa135 and the jaw made up of regions of Rpa190 and Rpa12. In vivo, the suppressor allele RPA135-F301S restores normal rRNA synthesis and increases Pol I density on rDNA genes when Rpa49 is absent. Growth of the Rpa135-F301S mutant is impaired when combined with exosome mutation rrp6Δ and it massively accumulates pre-rRNA. Moreover, Pol I bearing Rpa135-F301S is a hyper-active RNA polymerase in an in vitro tailed-template assay. We conclude that RNA polymerase I can be engineered to produce more rRNA in vivo and in vitro. We propose that the mutated area undergoes a conformational change that supports the DNA insertion into the cleft of the enzyme resulting in a super-active form of Pol I.

Background Juvenile idiopathic arthritis (JIA) refers to a heterogeneous group of rheumatic conditions in children. Novel drugs have greatly improved disease outcomes; however, outcomes are impacted by limited awareness of the importance of early diagnosis and adequate treatment, and by differences in access across health systems. As a result, patients with JIA continue to be at risk for short- and long-term morbidity, as well as impacts on virtually all aspects of life of the child and family. Main body Literature on the socioeconomic burden of JIA is largely focused on healthcare costs, and the impact of JIA on patients, families, and communities is not well understood. High quality evidence on the impact of JIA is needed to ensure that patients are receiving necessary support, timely diagnostics, and adequate treatment, and to inform decision making and resource allocation. This commentary introduces the European Joint Programme on Rare Diseases: Producing an Arthritis Value Framework with Economic Evidence: Paving the Way for Rare Childhood Diseases (PAVE) project, which will co-develop a patient-informed value framework to measure the impact of JIA on individuals and on society. With a patient-centered approach, fundamental to PAVE is the involvement of three patient advocacy organizations from Canada, Israel, and Europe, as active research partners co-designing all project phases and ensuring robust patient and family engagement. The framework will build on the findings of projects from six countries: Canada, Germany, Switzerland, Spain, Israel, and Belgium, exploring costs, outcomes (health, well-being), and unmet needs (uveitis, mental health, equity). Conclusion This unique international collaboration will combine evidence on costs (from family to societal), outcomes (clinical, patient and family outcomes), and unmet needs, to co-design and build a framework with patients and families to capture the full impact of JIA. The framework will support the development of high-quality evidence, encompassing economic and clinical considerations, unmet needs, and patient perspectives, to inform equitable resource allocation, health system planning, and quality of care better aligned with the needs of children with JIA, their families, and communities. Knowledge gained from this novel approach may pave the way forward to be applied more broadly to other rare childhood diseases.

Heterochromatin protein 1 (HP1) is a multifunctional chromatin-associated protein conserved from fission yeast to mammals. HP1 has been suggested to drive heterochromatin formation via phase separation. However, there is seemingly conflicting evidence about HP1 phase-separating in different systems or not. Here, we assess the phase separation behavior of HP1 from fission yeast, fruit fly and mouse in vitro and in mammalian cells side-by-side. We find that HP1 from fission yeast and fly can undergo liquid-liquid phase separation and induce heterochromatin coalescence in mouse cells, in stark contrast to HP1 from mouse. Induced heterochromatin coalescence has only mild effects on gene expression. We link the decreasing phase separation propensity of HP1 homologs to their decreasing intrinsic disorder and their increasing sensitivity to HP1 paralogs antagonizing phase separation. Our work elucidates the relationship between phase separation, nuclear organization and gene expression, and highlights the evolutionary dimension of protein phase separation control.

ObjectivesRecent insights supporting the safety of live-attenuated vaccines and novel studies on the immunogenicity of vaccinations in the era of biological disease-modifying antirheumatic drugs in paediatric patients with autoimmune/inflammatory rheumatic diseases (pedAIIRD) necessitated updating the EULAR recommendations.MethodsRecommendations were developed using the EULAR standard operating procedures. Two international expert committees were formed to update the vaccination recommendations for both paediatric and adult patients with AIIRD. After a systematic literature review, separate recommendations were formulated for paediatric and adult patients. For pedAIIRD, six overarching principles and seven recommendations were formulated and provided with the level of evidence, strength of recommendation and Task Force level of agreement.ResultsIn general, the National Immunisation Programmes (NIP) should be followed and assessed yearly by the treating specialist. If possible, vaccinations should be administered prior to immunosuppressive drugs, but necessary treatment should never be postponed. Non-live vaccines can be safely given to immunosuppressed pedAIIRD patients. Mainly, seroprotection is preserved in patients receiving vaccinations on immunosuppression, except for high-dose glucocorticoids and B-cell depleting therapies. Live-attenuated vaccines should be avoided in immunosuppressed patients. However, it is safe to administer the measles–mumps–rubella booster and varicella zoster virus vaccine to immunosuppressed patients under specific conditions. In addition to the NIP, the non-live seasonal influenza vaccination should be strongly considered for immunosuppressed pedAIIRD patients.ConclusionsThese recommendations are intended for paediatricians, paediatric rheumatologists, national immunisation agencies, general practitioners, patients and national rheumatology societies to attain safe and effective vaccination and optimal infection prevention in immunocompromised pedAIIRD patients.

INTRODUCTION: Insulin gene VNTR was associated with polycystic ovary syndrome (PCOS) in some studies but not in others. This couldb be due to the heterogeneity of the definition of PCOS and/or the use of inappropriate gene mapping strategies. MATERIAL AND METHODS: In this investigation, the association of VNTR with PCOS was explored in a population of women from Central Europe (377 cases and 105 controls) in whom PCOS was diagnosed according to Rotterdam criteria. Seven SNPs: rs3842756 (G/A), rs3842755 (G/T), rs3842754 (C/T), rs3842753 (A/C), rs3842752 (C/T), rs3842748 (G/C), and rs689 (T/A) were genotyped in a portion of the population (160 cases and 95 controls) by sequencing or by SSO-PCR. Analysis of linkage disequilibrium (LD) pattern allowed selecting three tagSNPs (rs3842754, rs3842748, and rs689), which were genotyped in the rest of the population by KASPar. RESULTS: Six haplotypes were reconstructed, among which three (h1, h2 and h6) were more frequent. Statistical analysis allowed observation of the association of the SNP rs3842748, through its GC genotype, with obesity in PCOS (P = 0.049; OR CI95% 1,59 [1.00–2.51]) and in classical PCOS (YPCOS) (P = 0.010), as well as the correlation of the SNP rs689 and the pair of haplotypes h1/h1 with higher levels of testosteronaemia in the PCOS group, although this was at the limit of significance (P = 0.054) CONCLUSION: These results are in accordance with some studies in literature and highlight the role of insulin gene VNTR in complex metabolic disorders. (Endokrynol Pol 2015; 66 (3): 198–206)

IS 911 transposition involves a free circular transposon intermediate where the terminal inverted repeat sequences are connected. Transposase synthesis is usually driven by a weak promoter, p IRL , in the left end (IRL). Circle junction formation creates a strong promoter, p junc , with a −35 sequence located in the right end and the −10 sequence in the left. p junc assembly would permit an increase in synthesis of transposase from the transposon circle, which would be expected to stimulate integration. Insertion results in p junc disassembly and a return to the low p IRL ‐ driven transposase levels. We demonstrate that p junc plays an important role in regulating IS 911 transposition. Inactivation of p junc strongly decreased IS 911 transposition when transposase was produced in its natural configuration. This novel feedback mechanism permits transient and controlled activation of integration only in the presence of the correct (circular) intermediate. We have also investigated other members of the IS 3 and other IS families. Several, but not all, IS 3 family members possess p junc equivalents, underlining that the regulatory mechanisms adopted to fine‐tune transposition may be different.

Most transcriptional activity of exponentially growing cells is carried out by the RNA Polymerase I (Pol I), which produces a ribosomal RNA (rRNA) precursor. In budding yeast, Pol I is a multimeric enzyme with 14 subunits. Among them, Rpa49 forms with Rpa34 a Pol I-specific heterodimer (homologous to PAF53/CAST heterodimer in human Pol I), which might be responsible for the specific functions of the Pol I. Previous studies provided insight in the involvement of Rpa49 in initiation, elongation, docking and releasing of Rrn3, an essential Pol I transcription factor. Here, we took advantage of the spontaneous occurrence of extragenic suppressors of the growth defect of the rpa49 null mutant to better understand the activity of Pol I. Combining genetic approaches, biochemical analysis of rRNA synthesis and investigation of the transcription rate at the individual gene scale, we characterized mutated residues of the Pol I as novel extragenic suppressors of the growth defect caused by the absence of Rpa49. When mapped on the Pol I structure, most of these mutations cluster within the jaw-lobe module, at an interface formed by the lobe in Rpa135 and the jaw made up of regions of Rpa190 and Rpa12. In vivo, the suppressor allele RPA135-F301S restores normal rRNA synthesis and increases Pol I density on rDNA genes when Rpa49 is absent. Growth of the Rpa135-F301S mutant is impaired when combined with exosome mutation rrp6Δ and it massively accumulates pre-rRNA. Moreover, Pol I bearing Rpa135-F301S is a hyper-active RNA polymerase in an in vitro tailed-template assay. We conclude that wild-type RNA polymerase I can be engineered to produce more rRNA in vivo and in vitro. We propose that the mutated area undergoes a conformational change that supports the DNA insertion into the cleft of the enzyme resulting in a super-active form of Pol I.

Chromosome mechanical properties determine DNA folding and dynamics, and underlie all major nuclear functions. Here we combine modeling and real-time motion tracking experiments to infer the physical parameters describing chromatin fibers. In vitro, motion of nucleosome arrays can be accurately modeled by assuming a Kuhn length of 35-55 nm. In vivo, the amplitude of chromosome fluctuations is reduced, and depends on transcription. Transcription activation increases chromatin dynamics only if it involves gene relocalization, while global transcriptional inhibition augments the fluctuations, yet without relocalization. Chromatin fiber motion is accounted for by a model of equilibrium fluctuations of a polymer chain, in which random contacts along the chromosome contour induce an excess of internal friction. Simulations that reproduce chromosome conformation capture and imaging data corroborate this hypothesis. This model unravels the transient nature of chromosome contacts, characterized by a lifetime of ~2 seconds and a free energy of formation of ~1 kBT.