SUMOylation is a post-translational modification that affects a large number of proteins, many of which are nuclear. While the role of SUMOylation is beginning to be elucidated, it is clear that understanding the mechanisms that regulate the process is likely to be important. Control of the levels of SUMOylation is brought about through a balance of conjugating and deconjugating activities, i.e. of SUMO (small ubiquitin-related modifier) conjugators and ligases versus SUMO proteases. Although conjugation of SUMO to proteins can occur in the absence of a SUMO ligase, it is apparent that SUMO ligases facilitate the SUMOylation of specific subsets of proteins. Two SUMO ligases in Schizosaccharomyces pombe, Pli1 and Nse2, have been identified, both of which have roles in genome stability. We report here on a comparison between the properties of the two proteins and discuss potential roles for the proteins.

SUMO is a ubiquitin-like protein that is post-translationally attached to one or more lysine residues on target proteins. Despite having only 18% sequence identity with ubiquitin, SUMO contains the conserved ββαββαβ fold present in ubiquitin. However, SUMO differs from ubiquitin in having an extended N-terminus. In S. pombe the N-terminus of SUMO/Pmt3 is significantly longer than those of SUMO in S. cerevisiae, human and Drosophila. Here we investigate the role of this N-terminal region. We have used two dimensional gel electrophoresis to demonstrate that S. pombe SUMO/Pmt3 is phosphorylated, and that this occurs on serine residues at the extreme N-terminus of the protein. Mutation of these residues (in pmt3-1) results in a dramatic reduction in both the levels of high Mr SUMO-containing species and of total SUMO/Pmt3, indicating that phosphorylation of SUMO/Pmt3 is required for its stability. Despite the significant reduction in high Mr SUMO-containing species, pmt3-1 cells do not display an aberrant cell morphology or sensitivity to genotoxins or stress. Additionally, we demonstrate that two lysine residues in the N-terminus of S. pombe SUMO/Pmt3 (K14 and K30) can act as acceptor sites for SUMO chain formation in vitro. Inability to form SUMO chains results in aberrant cell and nuclear morphologies, including stretched and fragmented chromatin. SUMO chain mutants are sensitive to the DNA synthesis inhibitor, hydroxyurea (HU), but not to other genotoxins, such as UV, MMS or CPT. This implies a role for SUMO chains in the response to replication arrest in S. pombe.

IntroductionTreatments for amblyopia, the most common vision deficit in children, often have suboptimal results. Occlusion/atropine blurring are fraught with poor adherence, regression and recurrence. These interventions target only the amblyopic eye, failing to address imbalances of cortical input from the two eyes (‘suppression’). Dichoptic treatments manipulate binocular visual experience to rebalance input. Poor adherence in early trials of dichoptic therapies inspired our development of balanced binocular viewing (BBV), using movies as child-friendly viewable content. Small observational studies indicate good adherence and efficacy. A feasibility trial is needed to further test safety and gather information to design a full trial.Methods/analysisWe will carry out an observer-masked parallel-group phase 2a feasibility randomised controlled trial at two sites, randomising 44 children aged 3–8 years with unilateral amblyopia to either BBV or standard occlusion/atropine blurring, with 1:1 allocation ratio. We will assess visual function at baseline, 8 and 16 weeks. The primary outcome is intervention safety at 16 weeks, measured as change in interocular suppression, considered to precede the onset of potential diplopia. Secondary outcomes include safety at other time points, eligibility, recruitment/retention rates, adherence, clinical outcomes. We will summarise baseline characteristics for each group and assess the treatment effect using analysis of covariance. We will compare continuous clinical secondary endpoints between arms using linear mixed effect models, and report feasibility endpoints using descriptive statistics.Ethics/disseminationThis trial has been approved by the London-Brighton & Sussex Research Ethics Committee (18/LO/1204), National Health Service Health Research Authority and Medicines and Healthcare products Regulatory Agency. A lay advisory group will be involved with advising on and disseminating the results to non-professional audiences, including on websites of funder/participating institutions and inputting on healthcare professional audience children would like us to reach. Reporting to clinicians and scientists will be via internal and external meetings/conferences and peer-reviewed journals.Trial registration numberNCT03754153.

Plain English summaryUsher syndrome is the most common cause of deafblindness worldwide and is estimated to affect between 3 and 6 people in every 100,000. Children are born with hearing loss and develop sight loss in their early years of life. A barrier to the involvement and participation of deafblind people in research is access to information in appropriate formats. The degree of sight and hearing impairment experienced by individuals is variable, so there is not a one size fits all solution. We held a research discussion group, that included five people with Usher syndrome, to consider people’s accessibility needs for an upcoming research project involving this condition.We have identified a number of considerations for including deafblind people in conversations about research: i) using appropriately sized meeting rooms which offer control over lighting, layout and sound; ii) where appropriate, ensuring written/printed materials are high contrast (e.g. black text with a yellow background) and in large (18 point and above), sans-serif fonts (e.g. Arial); iii) identifying the relevant communication support for the individual whether that be sign language interpretation, lip reading, hearing loop, speech to text reporting or a combination; iv) ensuring that there is access to emotional support for both people who are deafblind and their families before, during and after the research.The outcome of this work is a checklist of considerations when planning to hold a research conversation with someone who is deafblind and hinges on earlier interactions to identify the appropriate support needs for the individual.Abstract Background Usher syndrome is the most common cause of deafblindness worldwide. Children are born with hearing loss and develop sight loss in their early years of life. It is estimated to affect between 3 and 6 people in every 100,000. A barrier to the involvement and participation of deafblind people in research is access to information in appropriate formats. Individuals have varying degrees of sight and hearing impairment meaning there is not a singular solution to supporting all people’s communication needs. There is evidence that severe sight and hearing impairments are used as exclusion criteria in some research studies. This exclusion may extend into involvement activities. Methods Eight people, including five people with Usher syndrome, attended a research discussion group. Through this activity, we identified what to consider when looking to improve the experience of taking part in a discussion about research for deafblind individuals. Results Among contributors two people made use of standard British Sign Language interpretation and one communicated using hands-on signing. Contributors highlighted the limitations associated with signing and lip reading such as exhaustion and clear lines of sight as well as the need for additional formats such as speech to text reporting, and high contrast (e.g. black text with a yellow background) printouts with large (18 point and above), sans-serif font...