How the ubiquitin proteasome system regulates the regulators of transcription

Ubiquitination regulation of aerobic glycolysis in cancer

Aerobic glycolysis, or the Warburg effect, is regarded as a critical part of metabolic reprogramming and plays a crucial role in the occurrence and development of tumours. Ubiquitination and deubiquitination, essential post-translational modifications, have attracted increasing attention with regards to the regulation of metabolic reprogramming in cancer. However, the mechanism of ubiquitination in glycolysis remains unclear. In this review, we discuss the roles of ubiquitination and deubiquitination in regulating glycolysis, and their involvement in regulating important signalling pathways, enzymes, and transcription factors. Focusing on potential mechanisms may provide novel strategies for cancer treatment.

Progression of Myopia in School-Aged Children After COVID-19 Home Confinement

Question

Is home confinement due to coronavirus disease 2019 associated with the burden of myopia?

Findings

In this cross-sectional study that included 194 904 photoscreening tests conducted in 123 535 children, a substantial myopic shift (−0.3 diopters) was noted after home confinement due to coronavirus disease 2019 for children aged 6 to 8 years. The prevalence of myopia increased 1.4 to 3 times in 2020 compared with the previous 5 years.

Meaning

Home confinement due to coronavirus disease 2019 appeared to be associated with a substantial myopic shift in children; younger (aged 6-8 years) children’s refractive status may be more sensitive to environmental changes than older children, given that they are in an important period for the development of myopia.

Importance

Time spent in outdoor activities has decreased owing to home confinement for the coronavirus disease 2019 (COVID-19) pandemic. Concerns have been raised about whether home confinement may have worsened the burden of myopia owing to substantially decreased time spent outdoors and increased screen time at home.

Objective

To investigate the refractive changes and prevalence of myopia in school-aged children during the COVID-19 home confinement.

Design, Setting, and Participants

A prospective cross-sectional study using school-based photoscreenings in 123 535 children aged 6 to 13 years from 10 elementary schools in Feicheng, China, was conducted. The study was performed during 6 consecutive years (2015-2020). Data were analyzed in July 2020.

Exposures

Noncycloplegic photorefraction was examined using a photoscreener device.

Main Outcomes and Measures

The spherical equivalent refraction was recorded for each child and the prevalence of myopia for each age group during each year was calculated. The mean spherical equivalent refraction and prevalence of myopia were compared between 2020 (after home confinement) and the previous 5 years for each age group.

Results

Of the 123 535 children included in the study, 64 335 (52.1%) were boys. A total of 194 904 test results (389 808 eyes) were included in the analysis. A substantial myopic shift (approximately −0.3 diopters [D]) was found in the 2020 school-based photoscreenings compared with previous years (2015-2019) for younger children aged 6 (−0.32 D), 7 (−0.28 D), and 8 (−0.29 D) years. The prevalence of myopia in the 2020 photoscreenings was higher than the highest prevalence of myopia within 2015-2019 for children aged 6 (21.5% vs 5.7%), 7 (26.2% vs 16.2%), and 8 (37.2% vs 27.7%) years. The differences in spherical equivalent refraction and the prevalence of myopia between 2020 and previous years were minimal in children aged 9 to 13 years.

Conclusions and Relevance

Home confinement during the COVID-19 pandemic appeared to be associated with a significant myopic shift for children aged 6 to 8 years according to 2020 school-based photoscreenings. However, numerous limitations warrant caution in the interpretation of these associations, including use of noncycloplegic refractions and lack of orthokeratology history or ocular biometry data. Younger children’s refractive status may be more sensitive to environmental changes than older ages, given the younger children are in a critical period for the development of myopia.

School-based epidemiology study of myopia in Tianjin, China

PURPOSE

To study the epidemiology of myopia in school-aged children in Tianjin and the relationship between visual acuity-based screening and refraction-based screening.

METHOD

This school-based prospective cohort study was performed on children from 42 elementary schools and 17 middle schools in Tianjin, China. Totally 14,551 children, ages ranging from 5 to 16 years, were included in this study. Uncorrected visual acuity (UCVA) was determined by logarithmic tumbling E chart. Non-cycloplegic photorefraction was examined by the Spot (v2.1.4) photoscreener. The relationship between the UCVA and refractive error was investigated for different age groups.

RESULTS

The overall prevalence of myopia at this school based screen is 78.2%, ranged from 10% at age of 5 to 95% at age of 16. The most dramatic increase in prevalence is from age of 6 (14.8%) to age of 7 (38.5%). The overall prevalence of high myopia is 2.5%. UCVA is found corresponding to spherical equivalent refraction (SER) in a manner of normal distribution and is significantly affected by age. When using UCVA to estimate the prevalence of myopia, the overall sensitivity and specificity are 0.824 and 0.820, respectively. Age-dependent optimal cutoff points and 95% confident intervals of such estimation are reported.

CONCLUSIONS

Myopia is heavily affecting school-aged children in Tianjin, China. The refraction screening is preferable for myopia screening, whereas the UCVA screening results need to be interpreted in an age-dependent manner for myopia estimation.

Cell cycle-dependent localization of the proteasome to chromatin

An integrative understanding of nuclear events including transcription in normal and cancer cells requires comprehensive and quantitative measurement of protein dynamics that underlie such events. However, the low abundance of most nuclear proteins hampers their detailed functional characterization. We have now comprehensively quantified the abundance of nuclear proteins with the use of proteomics approaches in both normal and transformed human diploid fibroblasts. We found that subunits of the 26S proteasome complex were markedly down-regulated in the nuclear fraction of the transformed cells compared with that of the wild-type cells. The intranuclear proteasome abundance appeared to be inversely related to the rate of cell cycle progression, with restraint of the cell cycle being associated with an increase in the amount of proteasome subunits in the nucleus, suggesting that the nuclear proteasome content is dependent on the cell cycle. Furthermore, chromatin enrichment for proteomics (ChEP) analysis revealed enrichment of the proteasome in the chromatin fraction of quiescent cells and its apparent dissociation from chromatin in transformed cells. Our results thus suggest that translocation of the nuclear proteasome to chromatin may play an important role in control of the cell cycle and oncogenesis through regulation of chromatin-associated transcription factors.

Compared performance of Spot and SW800 photoscreeners on Chinese children

Purpose

To evaluate the effectiveness of Spot photoscreener and SW800 vision screener in detecting amblyopia risk factors in Chinese children between 4 and 6 years of age.

Methods

One hundred and thirteen children (226 eyes) underwent complete ophthalmologic examination, cycloplegic retinoscopy refraction, prism cover tests and photoscreen using both Spot (v2.1.4) and SW800 (v1.0.1.0) photoscreeners. The agreement of results obtained from photoscreener and retinoscopy was evaluated by paired t-test as well as Pearson correlation test. The sensitivity and specificity of detecting amblyopia risk factors were calculated based on the American Association of Pediatric Ophthalmology and Strabismus 2013 guidelines. The overall effectiveness of detecting amblyopia risk factors by using either photoscreener was analysed by receiver operating characteristic (ROC) curves.

Results

A strong linear agreement was observed between Spot and retinoscopy (p<0.01) in aspects of spherical equivalent (SE, Pearson’s r=0.95), dioptre sphere (DS, r=0.97), dioptre cylinder (DC, r=0.84) and horizontal deviation (Hdev, r=0.91), with overall −0.17 D myopic shift of SE. Significant correlation was also shown between SW800 and retinoscopy (p<0.01) in aspects of SE (r=0.90), DS (r=0.93), DC (r=0.82) and Hdev (r=0.80), with overall −0.12 D myopic shift of SE. The overall sensitivity and specificity in detecting amblyopia risk factors were 94.0% and 80.0% for Spot and 88.8% and 81.1% for SW800.

Conclusion

The measurements of Spot and SW800 photoscreener showed a strong agreement with cycloplegic retinoscopy refraction and prism cover tests. The performance of both screeners in detecting individual amblyopia risk factors is satisfactory. ROC analysis indicates that the Spot and SW800 performed very similarly in detecting amblyopia risk factors.

Regulation of transcriptional activators by DNA-binding domain ubiquitination

Ubiquitin is a key component of the regulatory network that maintains gene expression in eukaryotes, yet the molecular mechanism(s) by which non-degradative ubiquitination modulates transcriptional activator (TA) function is unknown. Here endogenous p53, a stress-activated transcription factor required to maintain health, is stably monoubiquitinated, following pathway activation by IR or Nutlin-3 and localized to the nucleus where it becomes tightly associated with chromatin. Comparative structure-function analysis and in silico modelling demonstrate a direct role for DNA-binding domain (DBD) monoubiquitination in TA activation. When attached to the DBD of either p53, or a second TA IRF-1, ubiquitin is orientated towards, and makes contact with, the DNA. The contact is made between a predominantly cationic surface on ubiquitin and the anionic DNA. Our data demonstrate an unexpected role for ubiquitin in the mechanism of TA-activity enhancement and provides insight into a new level of transcriptional regulation.

Fungal mediator tail subunits contain classical transcriptional activation domains

Classical activation domains within DNA-bound eukaryotic transcription factors make weak interactions with coactivator complexes, such as Mediator, to stimulate transcription. How these interactions stimulate transcription, however, is unknown. The activation of reporter genes by artificial fusion of Mediator subunits to DNA binding domains that bind to their promoters has been cited as evidence that the primary role of activators is simply to recruit Mediator. We have identified potent classical transcriptional activation domains in the C termini of several tail module subunits of Saccharomyces cerevisiae, Candida albicans, and Candida dubliniensis Mediator, while their N-terminal domains are necessary and sufficient for their incorporation into Mediator but do not possess the ability to activate transcription when fused to a DNA binding domain. This suggests that Mediator fusion proteins actually are functioning in a manner similar to that of a classical DNA-bound activator rather than just recruiting Mediator. Our finding that deletion of the activation domains of S. cerevisiae Med2 and Med3, as well as C. dubliniensis Tlo1 (a Med2 ortholog), impairs the induction of certain genes shows these domains function at native promoters. Activation domains within coactivators are likely an important feature of these complexes and one that may have been uniquely leveraged by a common fungal pathogen.