ZNF827 is a single-stranded DNA binding protein that regulates the ATR-CHK1 DNA damage response pathway.

The ATR-CHK1 DNA damage response pathway becomes activated by the exposure of RPA-coated single-stranded DNA (ssDNA) that forms as an intermediate during DNA damage and repair, and as a part of the replication stress response. Here, we identify ZNF827 as a component of the ATR-CHK1 kinase pathway. We demonstrate that ZNF827 is a ssDNA binding protein that associates with RPA through concurrent binding to ssDNA intermediates. These interactions are dependent on two clusters of C2H2 zinc finger motifs within ZNF827. We find that ZNF827 accumulates at stalled forks and DNA damage sites, where it activates ATR and promotes the engagement of homologous recombination-mediated DNA repair. Additionally, we demonstrate that ZNF827 depletion inhibits replication initiation and sensitizes cancer cells to the topoisomerase inhibitor topotecan, revealing ZNF827 as a therapeutic target within the DNA damage response pathway.

Multiplexed Long-Range Electrohydrodynamic Transport and Nano-Optical Trapping with Cascaded Bowtie Photonic Crystal Nanobeams.

Photonic crystal cavities with bowtie defects that combine ultrahigh Q and ultralow mode volume are theoretically studied for low-power nanoscale optical trapping. By harnessing the localized heating of the water layer near the bowtie region, combined with an applied alternating current electric field, this system provides long-range electrohydrodynamic transport of particles with average radial velocities of 30 µm/s towards the bowtie region on demand by switching the input wavelength. Once transported to a given bowtie region, synergistic interaction of optical gradient and attractive negative thermophoretic forces stably trap a 10 nm quantum dot in a potential well with a depth of 10 k_{B}T using a mW input power.

A DNA-fiber protocol for single molecule analysis of telomere (SMAT) length and extension events in cancer cells.

Alternative lengthening of telomeres (ALT) is a homologous recombination-based telomere maintenance mechanism. It is active in approximately 10-15% of cancers. We present a DNA-fiber protocol, combining YOYO-1 staining of genomic DNA, telomere fluorescence in situ hybridization (FISH), and EdU labeling of nascent DNA, to measure telomere extension events in ALT cancer cells. The protocol can be used to delineate ALT-mediated telomere extension. For complete details on the use and execution of this protocol, please refer to Barroso-Gonzalez et al. (2021).

Photonic crystals with split ring unit cells for subwavelength light confinement.

Here we report a photonic crystal with a split ring unit cell shape that demonstrates an order of magnitude larger peak electric field energy density compared with that of a traditional photonic crystal. Split ring photonic crystals possess several subwavelength tuning parameters, including split ring rotation angle and split width, which can be leveraged to modify light confinement for specific applications. Modifying the split ring's parameters allows for tuning of the peak electric field energy density in the split by over one order of magnitude and tuning of the air band edge wavelength by nearly 10 nm in the near infrared region. Designed to have highly focused optical energy in an accessible subwavelength gap, the split ring photonic crystal is well suited for applications including optical biosensing, optical trapping, and enhanced emission from a quantum dot or other nanoscale emitter that could be incorporated in the split.

Anti-recombination function of MutSα restricts telomere extension by ALT-associated homology-directed repair.

Alternative lengthening of telomeres (ALT) is a telomere-elongation mechanism observed in ∼15% of cancer subtypes. Current models indicate that ALT is mediated by homology-directed repair mechanisms. By disrupting MSH6 gene expression, we show that the deficiency of MutSα (MSH2/MSH6) DNA mismatch repair complex causes striking telomere hyperextension. Mechanistically, we show MutSα is specifically recruited to telomeres in ALT cells by associating with the proliferating-cell nuclear antigen (PCNA) subunit of the ALT telomere replisome. We also provide evidence that MutSα counteracts Bloom (BLM) helicase, which adopts a crucial role in stabilizing hyper-extended telomeres and maintaining the survival of MutSα-deficient ALT cancer cells. Lastly, we propose a model in which MutSα deficiency impairs heteroduplex rejection, leading to premature initiation of telomere DNA synthesis that coincides with an accumulation of telomere variant repeats (TVRs). These findings provide evidence that the MutSα DNA mismatch repair complex acts to restrain unwarranted ALT.

Progerin impairs 3D genome organization and induces fragile telomeres by limiting the dNTP pools.

Chromatin organization within the nuclear volume is essential to regulate many aspects of its function and to safeguard its integrity. A key player in this spatial scattering of chromosomes is the nuclear envelope (NE). The NE tethers large chromatin domains through interaction with the nuclear lamina and other associated proteins. This organization is perturbed in cells from Hutchinson-Gilford progeria syndrome (HGPS), a genetic disorder characterized by premature aging features. Here, we show that HGPS-related lamina defects trigger an altered 3D telomere organization with increased contact sites between telomeres and the nuclear lamina, and an altered telomeric chromatin state. The genome-wide replication timing signature of these cells is perturbed, with a shift to earlier replication for regions that normally replicate late. As a consequence, we detected a higher density of replication forks traveling simultaneously on DNA fibers, which relies on limiting cellular dNTP pools to support processive DNA synthesis. Remarkably, increasing dNTP levels in HGPS cells rescued fragile telomeres, and improved the replicative capacity of the cells. Our work highlights a functional connection between NE dysfunction and telomere homeostasis in the context of premature aging.

Telomere Length Measurement by Molecular Combing.

Telomeres are repetitive regions of DNA bound by specialized proteins at the termini of linear chromosomes that prevent the natural chromosome ends from being recognized as DNA double strand breaks. Telomeric DNA is gradually eroded with each round of cell division, resulting in the accumulation of critically short or dysfunctional telomeres that eventually trigger cellular senescence. Consequently, telomere length is indicative of the proliferative capacity of a cell. Multiple methods exist to measure telomere length and telomere content, but a simple and reliable technique to accurately measure individual telomere lengths is currently lacking. We have developed the Telomere length Combing Assay (TCA) to measure telomere length on stretched DNA fibers. We used TCA to measure telomere erosion in primary human fibroblasts, and to detect telomere lengthening in response to activation of telomere maintenance pathways. TCA was also used to accurately measure telomere length in healthy individuals, and to identify critically short telomeres in patients with telomere biology disorders. TCA is performed on isolated DNA, negating the need for cycling cells. TCA is amenable to semi-automated image analysis, and can be fully automated using the Genomic Vision molecular combing platform. This not only precludes sampling bias, but also provides the potential for high-throughput applications and clinical development. TCA is a simple and versatile technique to measure the distribution of individual telomere lengths in a cell population, offering improved accuracy, and more detailed biological insight for telomere length measurement applications.

Author Correction: The FANCM-BLM-TOP3A-RMI complex suppresses alternative lengthening of telomeres (ALT).

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

The FANCM-BLM-TOP3A-RMI complex suppresses alternative lengthening of telomeres (ALT).

The collapse of stalled replication forks is a major driver of genomic instability. Several committed mechanisms exist to resolve replication stress. These pathways are particularly pertinent at telomeres. Cancer cells that use Alternative Lengthening of Telomeres (ALT) display heightened levels of telomere-specific replication stress, and co-opt stalled replication forks as substrates for break-induced telomere synthesis. FANCM is a DNA translocase that can form independent functional interactions with the BLM-TOP3A-RMI (BTR) complex and the Fanconi anemia (FA) core complex. Here, we demonstrate that FANCM depletion provokes ALT activity, evident by increased break-induced telomere synthesis, and the induction of ALT biomarkers. FANCM-mediated attenuation of ALT requires its inherent DNA translocase activity and interaction with the BTR complex, but does not require the FA core complex, indicative of FANCM functioning to restrain excessive ALT activity by ameliorating replication stress at telomeres. Synthetic inhibition of FANCM-BTR complex formation is selectively toxic to ALT cancer cells.

Solvation behavior of carbonate-based electrolytes in sodium ion batteries.

Sodium ion batteries are on the cusp of being a commercially available technology. Compared to lithium ion batteries, sodium ion batteries can potentially offer an attractive dollar-per-kilowatt-hour value, though at the penalty of reduced energy density. As a materials system, sodium ion batteries present a unique opportunity to apply lessons learned in the study of electrolytes for lithium ion batteries; specifically, the behavior of the sodium ion in an organic carbonate solution and the relationship of ion solvation with electrode surface passivation. In this work the Li+ and Na+-based solvates were characterized using electrospray mass spectrometry, infrared and Raman spectroscopy, 17O, 23Na and pulse field gradient double-stimulated-echo pulse sequence nuclear magnetic resonance (NMR), and conductivity measurements. Spectroscopic evidence demonstrate that the Li+ and Na+ cations share a number of similar ion-solvent interaction trends, such as a preference in the gas and liquid phase for a solvation shell rich in cyclic carbonates over linear carbonates and fluorinated carbonates. However, quite different IR spectra due to the PF6- anion interactions with the Na+ and Li+ cations were observed and were rationalized with the help of density functional theory (DFT) calculations that were also used to examine the relative free energies of solvates using cluster - continuum models. Ion-solvent distances for Na+ were longer than Li+, and Na+ had a greater tendency towards forming contact pairs compared to Li+ in linear carbonate solvents. In tests of hard carbon Na-ion batteries, performance was not well correlated to Na+ solvent preference, leading to the possibility that Na+ solvent preference may play a reduced role in the passivation of anode surfaces and overall Na-ion battery performance.

New cardiac models of care reduce patient access to specialist nurses: a Victorian cross-sectional pilot study.

BACKGROUND: Several studies have shown that the acuity and complexity of patients admitted to coronary care units is rising. Advances in medical technology and management of these patients have resulted in shorter lengths of hospital stay. Together, these changing care patterns have led to an emergence of new models of care delivery that differ from traditional coronary care units (CCU). The effect of these new models on workforce and resources in this area is unknown. AIM: To describe the workforce and workplace resources of adult CCUs in Victoria, Australia. METHOD: This pilot study used an investigator-developed survey to audit all adult CCUs operating in Victoria in 2010. RESULTS: A total of 24 CCUs participated in the audit of which the majority were located in metropolitan public hospitals. In terms of model of care of CCUs: 25% (6) of CCUs were a combination of a CCU/cardiology ward, 17% (4) a combined CCU/ICU or combined CCU/ICU/HDU and 12.5% (3) of CCUs were a dedicated unit. Only 15% (4) of all units met the international standards for a nursing workforce with critical care qualifications. The CCU/day procedure/HDU models had 24% of critical care qualified staff followed by CCU/cardiology ward model with 35% compared to an average of 54-80% of qualified staff in the other models of care of CCU. CONCLUSIONS: This pilot study has highlighted the heterogeneity in models of CCU and a shortage of qualified critical care nurses, particularly in the CCU/cardiology ward model. This may have implications for the quality of care delivered in CCUs.

Annual resuscitation competency assessments: a review of the evidence.

BACKGROUND: Australian critical care nurses generally undertake assessment of resuscitation competencies on an annual or biannual basis. International resuscitation evidence and guidelines released in 2010 do not support this practice, instead advocating more frequent retraining. AIM: To review the evidence for annual assessment of resuscitation knowledge and skills, and for the efficacy of resuscitation training practices. METHODS: A search of the Medline and CINAHL databases was conducted using the key search words/terms 'resuscitation' 'advanced life support' 'advanced cardiac life support' 'assessment' 'cardiac arrest', 'in-hospital cardiac arrest', 'competence', 'training', 'ALS', 'ACLS' 'course' and 'competency'. The search was limited to English language publications produced during the last 10 years. The International Liaison Committee On Resuscitation worksheets were reviewed for key references, as were the reference lists of articles from the initial search. RESULTS: There is little evidence to support the current practice of annual resuscitation competency assessments. Theoretical knowledge has no correlation with resuscitation performance, and current practical assessment methods are problematic. Both knowledge and skills decline well before the 12-month mark. There is emerging support in the literature for frequent practice sessions using simulation technology. CONCLUSION: The current practice of annual assessments is not supported by evidence. Emerging evidence for regular resuscitation practice is not conclusive, but it is likely to produce better outcomes. Changing practice in Australia also represents an opportunity to generate data to inform practice further.