The high fidelity and unique error signature of human DNA polymerase ε

Bulk replicative DNA synthesis in eukaryotes is highly accurate and efficient, primarily because of two DNA polymerases (Pols): Pols δ and ε. The high fidelity of these enzymes is due to their intrinsic base selectivity and proofreading exonuclease activity which, when coupled with post-replication mismatch repair, helps to maintain human mutation rates at less than one mutation per genome duplication. Conditions that reduce polymerase fidelity result in increased mutagenesis and can lead to cancer in mice. Whereas yeast Pol ε has been well characterized, human Pol ε remains poorly understood. Here, we present the first report on the fidelity of human Pol ε. We find that human Pol ε carries out DNA synthesis with high fidelity, even in the absence of its 3′→5′ exonucleolytic proofreading and is significantly more accurate than yeast Pol ε. Though its spectrum of errors is similar to that of yeast Pol ε, there are several notable exceptions. These include a preference of the human enzyme for T→A over A→T transversions. As compared with other replicative DNA polymerases, human Pol ε is particularly accurate when copying homonucleotide runs of 4–5 bases. The base pair substitution specificity and high fidelity for frameshift errors observed for human Pol ε are distinct from the errors made by human Pol δ

Stand Out in Class: restructuring theclassroom environment to reducesedentary behaviour in 9–10-year-olds—study protocol for a pilot clusterrandomised controlled trial

Background: Sedentary behaviour (sitting) is a highly prevalent negative health behaviour, with individuals of allages exposed to environments that promote prolonged sitting. Excessive sedentary behaviour adversely affects health inchildren and adults. As sedentary behaviour tracks from childhood into adulthood, the reduction of sedentary time inyoung people is key for the prevention of chronic diseases that result from excessive sitting in later life. The sedentaryschool classroom represents an ideal setting for environmentalchange, through the provision of sit-stand desks. Whilstthe use of sit-stand desks in classrooms demonstrates positiveeffects in some key outcomes, evidence is currently limitedby small samples and/or short intervention durations, withfewstudiesadoptingrandomisedcontrolledtrial(RCT)designs. This paper describes the protocol of a pilot cluster RCT of a sit-stand desk interventioninprimaryschoolclassrooms.Methods/Design:A two-arm pilot cluster RCT will be conducted in eight primary schools (four intervention, four control)with at least 120 year 5 children (aged 9–10 years). Sit-stand desks will replace six standard desks in the interventionclassrooms. Teachers will be encouraged to ensure all pupils are exposed to the sit-stand desks for at least 1 h/dayon average using a rotation system. Schools assigned to the control arm will continue with their usual practice, noenvironmental changes will be made to their classrooms. Measurements will be taken at baseline, beforerandomisation, and at the end of the schools’academic year. In this study, the primary outcomes of interest will beschool and participant recruitment and attrition, acceptability of the intervention, and acceptability and complianceto the proposed outcome measures (including activPAL-measured school-time and school-day sitting, accelerometer-measured physical activity, adiposity, blood pressure, cognitive function, academic progress, engagement, andbehaviour) for inclusion in a definitive trial. A full process evaluation and an exploratory economic evaluation willalso be conducted to further inform a definitive tria

Distinctive activities of dna polymerases during human dna replication

The contributions of human DNA polymerases (pols) alpha, delta and epsilon during S-phase progression were studied in order to elaborate how these enzymes co-ordinate their functions during nuclear DNA replication. Pol delta was three to four times more intensely UV cross-linked to nascent DNA in late compared with early S phase, whereas the cross-linking of pols alpha and epsilon remained nearly constant throughout the S phase. Consistently, the chromatin-bound fraction of pol delta, unlike pols alpha and epsilon, increased in the late S phase. Moreover, pol delta neutralizing antibodies inhibited replicative DNA synthesis most efficiently in late S-phase nuclei, whereas antibodies against pol epsilon were most potent in early S phase. Ultrastructural localization of the pols by immuno-electron microscopy revealed pol epsilon to localize predominantly to ring-shaped clusters at electron-dense regions of the nucleus, whereas pol delta was mainly dispersed on fibrous structures. Pol alpha and proliferating cell nuclear antigen displayed partial colocalization with pol delta and epsilon, despite the very limited colocalization of the latter two pols. These data are consistent with models where pols delta and epsilon pursue their functions at least partly independently during DNA replication

Distinctive activities of dna polymerases during human dna replication

The contributions of human DNA polymerases (pols) alpha, delta and epsilon during S-phase progression were studied in order to elaborate how these enzymes co-ordinate their functions during nuclear DNA replication. Pol delta was three to four times more intensely UV cross-linked to nascent DNA in late compared with early S phase, whereas the cross-linking of pols alpha and epsilon remained nearly constant throughout the S phase. Consistently, the chromatin-bound fraction of pol delta, unlike pols alpha and epsilon, increased in the late S phase. Moreover, pol delta neutralizing antibodies inhibited replicative DNA synthesis most efficiently in late S-phase nuclei, whereas antibodies against pol epsilon were most potent in early S phase. Ultrastructural localization of the pols by immuno-electron microscopy revealed pol epsilon to localize predominantly to ring-shaped clusters at electron-dense regions of the nucleus, whereas pol delta was mainly dispersed on fibrous structures. Pol alpha and proliferating cell nuclear antigen displayed partial colocalization with pol delta and epsilon, despite the very limited colocalization of the latter two pols. These data are consistent with models where pols delta and epsilon pursue their functions at least partly independently during DNA replication

The Transformative Power of Inclusion, Diversity, Equity, Accessibility, and Social Justice in Interprofessional Education and Collaborative Practice – Discussion Paper

In the ever-evolving landscape of healthcare and education, the principles of Inclusion, Diversity, Equity, Accessibility, and Social Justice have emerged as guiding beacons for Interprofessional Education and Collaborative Practice (IPECP). We recognize that these foundational elements are not mere buzzwords, they are the pillars upon which our collective impact rests. In this Discussion Paper, we unravel the significance of inclusion, diversity, equity, accessibility, and social justice in shaping a more compassionate, equitable, and effective healthcare ecosystem