Development of an infection prevention and control pathway to facilitate high-throughput cataract surgery in Scotland.

INTRODUCTION: Cataract surgery offers significant improvement to quality of life for patients with cataracts. However, there are growing waiting lists and challenges in providing this type of surgery in a timely manner. Feedback from stakeholders had previously indicated infection prevention and control (IPC) as a potential barrier to high-throughput surgery. Antimicrobial Resistance and Healthcare Associated Infection Scotland was asked to support the implementation of high-throughput cataract surgery aimed at addressing these challenges. AIM: To develop an IPC pathway to facilitate high-throughput surgery. This would be based on best practice, and would address any barriers identified by stakeholders. METHODS: A short life working group with input from key stakeholders, including clinical teams, was established. A rapid literature review was also undertaken. RESULTS: An agreed patient pathway was developed, with the aim of helping to facilitate high-throughput surgery. Pre-, intra- and postoperative phases were considered. Where literature was unavailable, expert/consensus opinion was utilized. Facilities for high-throughput surgery were also considered, including the Jack and Jill theatre arrangement which lends itself well to this concept. CONCLUSION: Through collaboration with stakeholders, an IPC pathway was developed to facilitate high-throughput cataract surgery and address any potential IPC barriers to implementation. The process and the output described could be utilized to develop similar pathways for other surgeries that lend themselves well to high throughput, improving quality of life for patients and reducing waiting times. This study highlights the importance of establishing surveillance for postoperative endophthalmitis following implementation.

STAMP-Based Digital CRISPR-Cas13a for Amplification-Free Quantification of HIV-1 Plasma Viral Loads.

Quantification of HIV RNA in plasma is critical for identifying the disease progression and monitoring the effectiveness of antiretroviral therapy. While RT-qPCR has been the gold standard for HIV viral load quantification, digital assays could provide an alternative calibration-free absolute quantification method. Here, we reported a Self-digitization Through Automated Membrane-based Partitioning (STAMP) method to digitalize the CRISPR-Cas13 assay (dCRISPR) for amplification-free and absolute quantification of HIV-1 viral RNAs. The HIV-1 Cas13 assay was designed, validated, and optimized. We evaluated the analytical performances with synthetic RNAs. With a membrane that partitions ∼100 nL of reaction mixture (effectively containing 10 nL of input RNA sample), we showed that RNA samples spanning 4 orders of dynamic range between 1 fM (∼6 RNAs) to 10 pM (∼60k RNAs) could be quantified as fast as 30 min. We also examined the end-to-end performance from RNA extraction to STAMP-dCRISPR quantification using 140 µL of both spiked and clinical plasma samples. We demonstrated that the device has a detection limit of approximately 2000 copies/mL and can resolve a viral load change of 3571 copies/mL (equivalent to 3 RNAs in a single membrane) with 90% confidence. Finally, we evaluated the device using 140 µL of 20 patient plasma samples (10 positives and 10 negatives) and benchmarked the performance with RT-PCR. The STAMP-dCRISPR results agree very well with RT-PCR for all negative and high positive samples with Ct < 32. However, the STAMP-dCRISPR is limited in detecting low positive samples with Ct > 32 due to the subsampling errors. Our results demonstrated a digital Cas13 platform that could offer an accessible amplification-free quantification of viral RNAs. By further addressing the subsampling issue with approaches such as preconcentration, this platform could be further exploited for quantitatively determining viral load for an array of infectious diseases.

Exploring Patients' Trust from a New Perspective. A Text-Analysis Study.

The concept of trust has been extensively studied within the field of medicine. Yet, a list of factors that clearly influence patients' trust is still under debate. Moreover, the methodological approaches found in literature have been reported to be lacking in their assessments and measurements of trust relationships in the medical field although trust between a patient and medical provider has been proven to increase adherence and improve health outcomes. Hence, adding data to this debate and exploring a reliable method to explore the construct of trust is relevant. This study collects new evidence of the most salient indicators of patient trust by using a narrative approach and highlighting the potential of this method in collecting indicators that could be used to build training that aims to increase patients' trust. We used the Linguistic Inquiry and Word Count software for text analysis to examine the spontaneous narrations of episodes of trust and distrust within the doctor-patient relationship with a sample of 82 adult patients. Results demonstrate the role of the emotional aspects of the doctor-patient relationship. Data highlights the importance of doctors' benevolence toward patients, and positive emotions seem to be deeply connected with any experience of trust, which leads patients to feel more secure. Methods are presented to use these insights to construct mechanisms that establish medical trust and allow providers to implement effective interventions.

Impact of a multipronged approach to reduce the incidence of Clostridioides difficile infections in hospitalized patients.

BACKGROUND: Effective approaches to reduce Clostridioides difficile infections (CDI) in hospitalized patients are needed. We report data from 3 years preceding and 3 years following interventions that proved successful, with detailed analysis of all cases the first year after implementation. METHODS: Interventions included a nursing protocol to identify cases present on admission by asking if the patient had 1 or more liquid stools in the last 24 hours, and a 2-step testing algorithm with samples positive by polymerase chain reaction (PCR) for the C. difficile toxin gene reflexing to an enzyme immunoassay (EIA) for the toxin antigen. RESULTS: Healthcare-associated infections due to CDI fell from ∼160 in each of the preceding 3 years to <65 in each of the subsequent 3 years (P < .001), while the ratio of observed-to-expected hospital-onset cases diminished to ∼0.50 (P < .02). In the first year, 395 samples were PCR(+), but only 118 (29.9%) of these were EIA(+). 55 (46.6%) of the PCR(+)/EIA(+) samples were from hospital day 1 or 2 and classified as present on admission. The mean time from stool collection to report of PCR results was ∼7.5 hours, and the EIA took on average only 68 additional minutes to be reported. CONCLUSIONS: The number of incident CDI cases can be dramatically decreased by implementing an admission screening question and a 2-step testing algorithm.

Impact of and Response to Cyberattacks in Radiation Oncology.

Cyberattacks on health care facilities are increasing and significantly affecting health care delivery throughout the world. The recent cyberattack on our hospital-based radiation facility exposed vulnerabilities of radiation oncology systems and highlighted the dependence of radiation treatment on integrated and complex radiation planning, delivery and verification systems. After the cyberattack on our health care facility, radiation oncology staff reconstructed patient information, schedules, and radiation plans from existing paper records and physicians developed a system to triage patients requiring immediate transfer of radiation treatment to nearby facilities. Medical physics and hospital information technology collaborated to restore services without access to the system backup or network connectivity. Ultimately, radiation treatments resumed incrementally as systems were restored and rebuilt. The experiences and lessons learned from this response were reviewed. The successes and shortcomings were incorporated into recommendations to provide guidance to other radiation facilities in preparation for a possible cyberattack. Our response and recommendations are intended to serve as a starting point to assist other facilities in cybersecurity preparedness planning. Because there is no one-size-fits-all response, each department should determine its specific vulnerabilities, risks, and available resources to create an individualized plan.

Potent Activation of NAD+-Dependent Deacetylase Sirt7 by Nucleosome Binding.

Sirtuin-7 (Sirt7) is a nuclear NAD+-dependent deacetylase with a broad spectrum of biological functions. Sirt7 overexpression is linked to several pathological states and enhances anticancer drug resistance, making the enzyme a promising target for the development of novel therapeutics. Despite a plethora of reported in vivo functions, the biochemical characterization of recombinant Sirt7 remains inadequate for the development of novel drug candidates. Here, we conduct an extensive biochemical analysis of Sirt7 using newly developed binding and kinetic assays to reveal that the enzyme preferentially interacts with and is activated by nucleosomes. Sirt7 activation by nucleic acids alone is effective toward long-chain acylated hydrophobic substrates, while only nucleosome binding leads to 105-fold activation of the deacetylase activity. Using endogenous chromatin and recombinant acetylated nucleosomes, we reveal that Sirt7 is one of the most efficient deacetylases in the sirtuin family and that its catalytic activity is limited by the rate of dissociation from deacetylated nucleosomes.

Radiation Therapy for Brain Metastases: ASCO Guideline Endorsement of ASTRO Guideline.

PURPOSE: American Society of Radiation Oncology (ASTRO) has developed a guideline on appropriate radiation therapy for brain metastases. ASCO has a policy and set of procedures for endorsing clinical practice guidelines that have been developed by other professional organizations. METHODS: "Radiation Therapy for Brain Metastases: An ASTRO Clinical Practice Guideline"2 was reviewed for developmental rigor by methodologists. An ASCO Endorsement Panel subsequently reviewed the content and the recommendations. RESULTS: The ASCO Endorsement Panel determined that the recommendations from the ASTRO guideline, published May 6, 2022, are clear, thorough, and based upon the most relevant scientific evidence. ASCO endorses "Radiation Therapy for Brain Metastases: An ASTRO Clinical Practice Guideline."2. RECOMMENDATIONS: Within the guideline, stereotactic radiosurgery (SRS) is recommended for patients with Eastern Cooperative Oncology Group performance status of 0-2 and up to four intact brain metastases, and conditionally recommended for patients with up to 10 intact brain metastases. The guideline provides detailed dosing and fractionation recommendations on the basis of the size of the metastases. For patients with resected brain metastases, radiation therapy (SRS or whole-brain radiation therapy [WBRT]) is recommended to improve intracranial disease control; if there are limited additional brain metastases, SRS is recommended over WBRT. For patients with favorable prognosis and brain metastases ineligible for surgery and/or SRS, WBRT is recommended with hippocampal avoidance where possible and the addition of memantine is recommended. For patients with brain metastases, limiting the single-fraction V12Gy to brain tissue to ≤ 10 cm3 is conditionally recommended.Additional information is available at www.asco.org/neurooncology-guidelines.

Discovery and Mechanism of Small Molecule Inhibitors Selective for the Chromatin-Binding Domains of Oncogenic UHRF1.

Chromatin abnormalities are common hallmarks of cancer cells, which exhibit alterations in DNA methylation profiles that can silence tumor suppressor genes. These epigenetic patterns are partly established and maintained by UHRF1 (ubiquitin-like PHD and RING finger domain-containing protein 1), which senses existing methylation states through multiple reader domains, and reinforces the modifications through recruitment of DNA methyltransferases. Small molecule inhibitors of UHRF1 would be important tools to illuminate molecular functions, yet no compounds capable of blocking UHRF1-histone binding in the context of the full-length protein exist. Here, we report the discovery and mechanism of action of compounds that selectively inhibit the UHRF1-histone interaction with low micromolar potency. Biochemical analyses reveal that these molecules are the first inhibitors to target the PHD finger of UHRF1, specifically disrupting histone H3 arginine 2 interactions with the PHD finger. Importantly, this unique inhibition mechanism is sufficient to displace binding of full-length UHRF1 with histones in vitro and in cells. Together, our study provides insight into the critical role of the PHD finger in driving histone interactions, and demonstrates that targeting this domain through a specific binding pocket is a tractable strategy for UHRF1-histone inhibition.

Treatment for Brain Metastases: ASCO-SNO-ASTRO Guideline.

PURPOSE: To provide guidance to clinicians regarding therapy for patients with brain metastases from solid tumors. METHODS: ASCO convened an Expert Panel and conducted a systematic review of the literature. RESULTS: Thirty-two randomized trials published in 2008 or later met eligibility criteria and form the primary evidentiary base. RECOMMENDATIONS: Surgery is a reasonable option for patients with brain metastases. Patients with large tumors with mass effect are more likely to benefit than those with multiple brain metastases and/or uncontrolled systemic disease. Patients with symptomatic brain metastases should receive local therapy regardless of the systemic therapy used. For patients with asymptomatic brain metastases, local therapy should not be deferred unless deferral is specifically recommended in this guideline. The decision to defer local therapy should be based on a multidisciplinary discussion of the potential benefits and harms that the patient may experience. Several regimens were recommended for non-small-cell lung cancer, breast cancer, and melanoma. For patients with asymptomatic brain metastases and no systemic therapy options, stereotactic radiosurgery (SRS) alone should be offered to patients with one to four unresected brain metastases, excluding small-cell lung carcinoma. SRS alone to the surgical cavity should be offered to patients with one to two resected brain metastases. SRS, whole brain radiation therapy, or their combination are reasonable options for other patients. Memantine and hippocampal avoidance should be offered to patients who receive whole brain radiation therapy and have no hippocampal lesions and 4 months or more expected survival. Patients with asymptomatic brain metastases with either Karnofsky Performance Status ≤ 50 or Karnofsky Performance Status < 70 with no systemic therapy options do not derive benefit from radiation therapy.Additional information is available at www.asco.org/neurooncology-guidelines.

Evaluation of the Onclarity HPV assay on the high-throughput COR system.

Background: Here we compare the performance of the high-throughput BD COR System (COR) to the Viper LT System (Viper) using the BD Onclarity HPV assay.Research Design and Methods: Remnant clinical specimens, contrived specimens in SurePath (BD) and PreservCyt (Hologic) media, and prospective clinical specimens in BD Cervical Brush Diluent (CBD) were tested. Outcomes included intra-laboratory agreement of Onclarity results on COR and inter-system agreement between COR and Viper.Results: Onclarity reproducibility on COR resulted in standard deviation and correlation of variation of Ct values ranging from 0.14 to 1.98 and 0.49% to 2.15%, respectively, for contrived specimens, and 0.9-3.08 and 2.89-9.21%, respectively, for clinical specimens. In the COR and Viper clinical agreement study, OPA for Onclarity ranged from 97.1%-98.9%, depending on the collection media type. PPA values for pooled, HPV(+) specimens at low positive (C95), and moderate positive (3XC95) target concentrations were ≥95.0% and 100%, respectively; PPA values associated with HPV 16, 18, 31, 45, 33/58, 52, 35/39/68, 51, and 56/59/66, individually, ranged from 93.8%-100%.Conclusions: Onclarity performance on COR is equivalent to Viper, and is accurate and reproducible for detection of all high-risk HPV genotypes, with a throughput of 330 results from a single 8-hour shift.

Cost-effectiveness of Prostate Radiation Therapy for Men With Newly Diagnosed Low-Burden Metastatic Prostate Cancer.

Importance: Prostate radiation therapy (PRT) is a treatment option in men with low-volume metastatic prostate cancer based on the results of the Systemic Therapy in Advancing or Metastatic Prostate Cancer: Evaluation of Drug Efficacy Arm H (STAMPEDE-H) trial. However, the cost-effectiveness of this treatment remains unaddressed. Objective: To assess the cost-effectiveness of PRT when added to androgen deprivation therapy (ADT) for men with low-volume metastatic hormone-sensitive prostate cancer (mHSPC). Design, Setting, and Participants: This economic evaluation used microsimulation modeling to evaluate the cost-effectiveness of adding PRT to ADT. A simulated cohort of 10 000 individuals with low-volume mHSPC was created. Data from men with low-volume mHSPC were extracted and analyzed from January 18, 2019, through July 4, 2020. Transition probabilities were extracted from the STAMPEDE-H study. Health states included stable disease, progression, second progression, and death. Individual grade 2 or higher genitourinary and gastrointestinal toxic events associated with PRT were tracked. Univariable deterministic and probabilistic sensitivity analyses explored uncertainty with regard to the model assumptions. Health state utility estimates were based on the published literature. Exposures: The combination of PRT and ADT using regimens of 20 fractions and 6 weekly fractions. Main Outcomes and Measures: Outcomes included net quality-adjusted life-years (QALYs), costs in US dollars, and incremental cost-effectiveness ratios. A strategy was classified as dominant if it was associated with higher QALYs at lower costs than the alternative and dominated if it was associated with fewer QALYs at higher costs than the alternative. Results: For the base case scenario of men 68 years of age with low-volume mHSPC, the modeled outcomes were similar to the target clinical data for overall survival, failure-free survival, and rates of PRT-related toxic effects. The addition of PRT was a dominant strategy compared with ADT alone, with a gain of 0.16 QALYs (95% CI, 0.15-0.17 QALYs) and a reduction in net costs by $19 472 (95% CI, $23 096-$37 362) at 37 months of follow-up and a gain of 0.81 QALYs (95% CI, 0.73-0.89 QALYs) and savings of $30 229 (95% CI, $23 096-$37 362) with lifetime follow-up. Conclusions and Relevance: In the economic evaluation, PRT was a dominant treatment strategy compared with ADT alone. These findings suggest that addition of PRT to ADT is a cost-effective treatment for men with low-volume mHSPC.

Understanding demand for, and feasibility of, centre-based child-care for poor urban households: a mixed methods study in Dhaka, Bangladesh.

BACKGROUND: Centre-based child-care has potential to provide multiple health and development benefits to children, families and societies. With rapid urbanisation, increasing numbers of low-income women work with reduced support from extended family, leaving a child-care vacuum in many low- and middle-income countries. We aimed to understand perceptions of, and demand for, centre-based child-care in Dhaka, Bangladesh among poor, urban households, and test the feasibility of delivering sustainable centre-based child-care. METHODS: We used sequential mixed methods including a household survey (n = 222) and qualitative interviews with care-givers (n = 16), community leaders (n = 5) and policy-makers (n = 5). We co-produced and piloted a centre-based child-care model over ten-months, documenting implementation. A co-design focus group with mothers, parents' meetings, and qualitative interviews with child-care centre users (n = 5), non-users (n = 3), ex-users (n = 3) and staff (2) were used to refine the model and identify implementation issues. RESULTS: We found 24% (95% CI: 16,37%) of care-givers reported turning-down paid work due to lack of child-care and 84% (95% CI:74, 91%) reported wishing to use centre-based child-care and were willing to pay up to 283 Takka (~$3.30) per month. Adjusted odds of reported need for child-care among slum households were 3.8 times those of non-slum households (95% CI: 1.4, 10). Implementation highlighted that poor households needed free child-care with food provided, presenting feasibility challenges. Meta-inference across quantitative and qualitative findings identified the impact of the urban environment on child-care through long working hours, low social capital and fears for child safety. These influences interacted with religious and social norms resulting in caution in using centre-based child-care despite evident need. CONCLUSION: Sustainable provision of centre-based care that focuses on early childhood development requires subsidy and careful design sensitive to the working lives of poor families, particularly women and must respond to the dynamics of the urban environment and community values. We recommend increased research and policy focus on the evaluation and scale-up of quality centre-based child-care, emphasising early-childhood development, to support low-income working families in urban areas.

Multivalent interactions drive nucleosome binding and efficient chromatin deacetylation by SIRT6.

The protein deacetylase SIRT6 maintains cellular homeostasis through multiple pathways that include the deacetylation of histone H3 and repression of transcription. Prior work suggests that SIRT6 is associated with chromatin and can substantially reduce global levels of H3 acetylation, but how SIRT6 is able to accomplish this feat is unknown. Here, we describe an exquisitely tight interaction between SIRT6 and nucleosome core particles, in which a 2:1 enzyme:nucleosome complex assembles via asymmetric binding with distinct affinities. While both SIRT6 molecules associate with the acidic patch on the nucleosome, we find that the intrinsically disordered SIRT6 C-terminus promotes binding at the higher affinity site through recognition of nucleosomal DNA. Together, multivalent interactions couple productive binding to efficient deacetylation of histones on endogenous chromatin. Unique among histone deacetylases, SIRT6 possesses the intrinsic capacity to tightly interact with nucleosomes for efficient activity.

Changing the Landscape: An Introduction to the Agricultural and Food Chemistry Technical Program at the 258th American Chemical Society National Meeting in San Diego.

This special issue of the Journal of Agricultural and Food Chemistry (JAFC) is a highlight of the Agricultural and Food Chemistry Division (AGFD) technical program at the 258th National Meeting of the American Chemical Society (ACS) in San Diego, CA, U.S.A., on August 25-29, 2019. At the conference, AGFD had 44 oral sessions at 19 symposia and 100 poster presentations with more than 400 abstract submissions. The technical program covered a broad range of current research and development topics in agricultural and food chemistry, including bioactive food components, diet and human nutrition, utilization of agricultural materials in food systems, food packaging, nanotechnology, and food safety, as well as several special award symposia. This is the first JAFC special issue that highlights an ACS national meeting program with joint efforts from AGFD.

Synbiotic Effect of Whole Grape Seed Flour and Newly Isolated Kefir Lactic Acid Bacteria on Intestinal Microbiota of Diet-Induced Obese Mice.

Alterations of intestinal microbiota by synbiotic action of pre- and probiotics may confer health benefits to the host. In this study, high-throughput sequencing of 16S rRNA was used to analyze intestinal microbiota in feces, and the relative abundance of intestinal bacteria was correlated with physiological data from a prior study of a synbiotic combination of flavonoid-rich wine grape seed flour (WGF) and two newly isolated kefir lactic acid bacteria (LAB) in diet-induced obese mice. The combination of WGF and LAB enhanced observed operational taxonomic units and Chao1 index compared to WGF alone, indicating an increase in the microbial community richness. The combination significantly enhanced abundance of Akkermansia muciniphila and Nocardia coeliaca and their abundance had an inverse relationship with body weight gain and adipose weight. In conclusion, the synbiotic effects of WGF and LAB on improvement of high-fat-diet-induced obesity are strongly linked to remodeling intestinal microbiota.

Methyl-Metabolite Depletion Elicits Adaptive Responses to Support Heterochromatin Stability and Epigenetic Persistence.

S-adenosylmethionine (SAM) is the methyl-donor substrate for DNA and histone methyltransferases that regulate epigenetic states and subsequent gene expression. This metabolism-epigenome link sensitizes chromatin methylation to altered SAM abundance, yet the mechanisms that allow organisms to adapt and protect epigenetic information during life-experienced fluctuations in SAM availability are unknown. We identified a robust response to SAM depletion that is highlighted by preferential cytoplasmic and nuclear mono-methylation of H3 Lys 9 (H3K9) at the expense of broad losses in histone di- and tri-methylation. Under SAM-depleted conditions, H3K9 mono-methylation preserves heterochromatin stability and supports global epigenetic persistence upon metabolic recovery. This unique chromatin response was robust across the mouse lifespan and correlated with improved metabolic health, supporting a significant role for epigenetic adaptation to SAM depletion in vivo. Together, these studies provide evidence for an adaptive response that enables epigenetic persistence to metabolic stress.

Attack rate and prey preference of Lasioseius subterraneous and Protogamasellus mica on four nematode species.

Plant parasitic nematodes are common and important global pests, causing over US$150 billion in crop losses across the agricultural sector worldwide. Meloidogyne javanica and Pratylenchus zeae are two of the most damaging plant-parasitic nematodes and there are limited options for their control. We evaluated the potential of a large (Lasioseius subterraneous) and a small (Protogamasellus mica) mesostigmatan mite as biological control agents of plant-parasitic nematodes. We tested the attack rate and reproductive potential of these two mite species on four nematode species: M. javanica (eggs), Pra. zeae (adults) and two microbivorous nematodes, Mesorhabditis sp. and Aphelenchus avenae (adults for both species). Each mite/nematode combination (1 mite:100 nematodes) was tested in six replicate arenas. In a separate trial, each mite species was presented with 50 A. avenae and 50 Pra. zeae in the same arena to determine prey preference. Both mite species significantly reduced the abundance of all nematode species used in the trials when compared to nematode-only controls. Lasioseius subterraneous consumed all available M. javanica eggs within 72 h. The larger mite had a significantly higher overall attack rate than the smaller mite, each consuming an average of 96 and 72 nematodes, respectively, within 72 h. However, both mites had a similar reproductive rate. Protogamasellus mica displayed a positive preference towards the plant parasitic nematode Pra. zeae over the fungal feeding A. avenae whereas L. subterraneous did not display a prey preference. Our results highlight the potential of these two predators to control plant parasitic nematodes, although further trials under field conditions are needed.

Hypocholesterolemic Effects of Expeller-Pressed and Solvent-Extracted Fruit Seed Oils and Defatted Pomegranate Seed Meals.

Consumptions of fruit seed oils and meals could potentially improve cardiovascular health by reducing plasma total cholesterol and low-density lipoprotein (LDL). The study objective was to compare the effectiveness of expeller-pressed and solvent-extracted grape, tomato, pomegranate seed oils, and defatted pomegranate meals in lowering plasma and hepatic cholesterol using hamster models. Hamsters were fed with fruit seed oils (FSO), defatted pomegranate seed meals (PDM), or control diets. After a 3-week feeding period, plasma total triglycerides of treatment diets were significantly lower. FSO also reduced total, very-low-density lipoprotein- (VLDL), and LDL-cholesterols, while PDM only lowered VLDL-cholesterols. Decreases in low-density and high-density lipoproteins (LDL/HDL) ratios were also observed in most treatments. In liver, triglycerides, total, and free cholesterol levels did not vary between control and treatments. There were no significant differences in lipid modulating properties between solvent-extracted and expeller-pressed oils. In conclusion, partial replacements of saturated fat in high-fat diets with tomato, pomegranate, and grape seed oils could effectively reduce plasma triglyceride levels and improve HDL/LDL ratios.

Mechanistic insights into histone deposition and nucleosome assembly by the chromatin assembly factor-1.

Eukaryotic chromatin is a highly dynamic structure with essential roles in virtually all DNA-dependent cellular processes. Nucleosomes are a barrier to DNA access, and during DNA replication, they are disassembled ahead of the replication machinery (the replisome) and reassembled following its passage. The Histone chaperone Chromatin Assembly Factor-1 (CAF-1) interacts with the replisome and deposits H3-H4 directly onto newly synthesized DNA. Therefore, CAF-1 is important for the establishment and propagation of chromatin structure. The molecular mechanism by which CAF-1 mediates H3-H4 deposition has remained unclear. However, recent studies have revealed new insights into the architecture and stoichiometry of the trimeric CAF-1 complex and how it interacts with and deposits H3-H4 onto substrate DNA. The CAF-1 trimer binds to a single H3-H4 dimer, which induces a conformational rearrangement in CAF-1 promoting its interaction with substrate DNA. Two CAF-1•H3-H4 complexes co-associate on nucleosome-free DNA depositing (H3-H4)2 tetramers in the first step of nucleosome assembly. Here, we review the progress made in our understanding of CAF-1 structure, mechanism of action, and how CAF-1 contributes to chromatin dynamics during DNA replication.