Bending forces and nucleotide state jointly regulate F-actin structure.

ATP-hydrolysis-coupled actin polymerization is a fundamental mechanism of cellular force generation1-3. In turn, force4,5 and actin filament (F-actin) nucleotide state6 regulate actin dynamics by tuning F-actin's engagement of actin-binding proteins through mechanisms that are unclear. Here we show that the nucleotide state of actin modulates F-actin structural transitions evoked by bending forces. Cryo-electron microscopy structures of ADP-F-actin and ADP-Pi-F-actin with sufficient resolution to visualize bound solvent reveal intersubunit interfaces bridged by water molecules that could mediate filament lattice flexibility. Despite extensive ordered solvent differences in the nucleotide cleft, these structures feature nearly identical lattices and essentially indistinguishable protein backbone conformations that are unlikely to be discriminable by actin-binding proteins. We next introduce a machine-learning-enabled pipeline for reconstructing bent filaments, enabling us to visualize both continuous structural variability and side-chain-level detail. Bent F-actin structures reveal rearrangements at intersubunit interfaces characterized by substantial alterations of helical twist and deformations in individual protomers, transitions that are distinct in ADP-F-actin and ADP-Pi-F-actin. This suggests that phosphate rigidifies actin subunits to alter the bending structural landscape of F-actin. As bending forces evoke nucleotide-state dependent conformational transitions of sufficient magnitude to be detected by actin-binding proteins, we propose that actin nucleotide state can serve as a co-regulator of F-actin mechanical regulation.

Structural mechanism for bidirectional actin cross-linking by T-plastin.

To orchestrate cell mechanics, trafficking, and motility, cytoskeletal filaments must assemble into higher-order networks whose local subcellular architecture and composition specify their functions. Cross-linking proteins bridge filaments at the nanoscale to control a network's µm-scale geometry, thereby conferring its mechanical properties and functional dynamics. While these interfilament linkages are key determinants of cytoskeletal function, their structural mechanisms remain poorly understood. Plastins/fimbrins are an evolutionarily ancient family of tandem calponin-homology domain (CHD) proteins required to construct multiple classes of actin networks, which feature diverse geometries specialized to power cytokinesis, microvilli and stereocilia biogenesis, and persistent cell migration. Here, we focus on the structural basis of actin network assembly by human T-plastin, a ubiquitously expressed isoform necessary for the maintenance of stable cellular protrusions generated by actin polymerization forces. By implementing a machine-learning-enabled cryo-electron microscopy pipeline for visualizing cross-linkers bridging multiple filaments, we uncover a sequential bundling mechanism enabling T-plastin to bridge pairs of actin filaments in both parallel and antiparallel orientations. T-plastin populates distinct structural landscapes in these two bridging orientations that are selectively compatible with actin networks featuring divergent architectures and functions. Our structural, biochemical, and cell biological data highlight inter-CHD linkers as key structural elements underlying flexible but stable cross-linking that are likely to be disrupted by T-plastin mutations that cause hereditary bone diseases.

Key Informants' Perceptions of Health Equity and Racial Justice Impacts of the 2019 Massachusetts An Act Modernizing Tobacco Control.

INTRODUCTION: The Massachusetts legislature passed An Act Modernizing Tobacco Control in November 2019 to restrict retail sales of flavored commercially manufactured tobacco products including menthol products, increase penalties for violating the law's provisions, and provide health insurance coverage for tobacco treatment. AIMS AND METHODS: This study explores key informants' perceptions of intended and unintended impacts of implementation of the 2019 Massachusetts statewide law through a health equity and racial justice lens. We conducted in-depth interviews with 25 key informants from three key informant groups (public health officials and advocates, clinicians, and school staff) between March 2021 and April 2022. Using deductive codes on unintended impacts of the implementation of the law's policies, we conducted a focused analysis to identify impacts that were perceived and observed by informants from different key informant groups. RESULTS: Perceived or observed impacts of the law were identified across multiple levels by key informants and included concerns related to three broad themes: 1) intended impacts on health equity and racial justice, 2) ongoing availability of restricted products undermining the intended impact of the law, and 3) inequitable targeting by the policies and enforcement among communities of color. CONCLUSIONS: Future evaluation is needed to assess the intended and unintended impacts of implementation of the Massachusetts law to maximize the potential of the policies to reduce tobacco-related health disparities. We discuss implications and recommendations for achieving a national policy and equitable enforcement of flavored tobacco sales restrictions. IMPLICATIONS: This qualitative study among 25 key informants including public health and tobacco control advocates, clinicians, and school staff obtained perspectives of intended and unintended health equity and racial justice impacts of the 2019 Massachusetts An Act Modernizing Tobacco Control. Findings and recommendations from this study can inform monitoring efforts to assess the law's impacts in Massachusetts and the adoption of similar flavored tobacco sales restrictions and other tobacco control policies in other states to maximize the health equity benefits and minimize unintended impacts.

The Use of Natural Language Processing to Assess Social Support in Patients With Advanced Cancer.

BACKGROUND: Data examining associations among social support, survival, and healthcare utilization are lacking in patients with advanced cancer. METHODS: We conducted a cross-sectional secondary analysis using data from a prospective longitudinal cohort study of 966 hospitalized patients with advanced cancer at Massachusetts General Hospital from 2014 through 2017. We used NLP to identify extent of patients' social support (limited versus adequate as defined by NLP-aided review of the Electronic Health Record (EHR)). Two independent coders achieved a Kappa of 0.90 (95% CI: 0.84-1.00) using NLP. Using multivariable regression models, we examined associations of social support with: 1) OS; 2) death or readmission within 90 days of hospital discharge; 3) time to readmission within 90 days; and 4) hospital length of stay (LOS). RESULTS: Patients' median age was 65 (range: 21-92) years, and a plurality had gastrointestinal (GI) cancer (34.3%) followed by lung cancer (19.5%). 6.2% (60/966) of patients had limited social support. In multivariable analyses, limited social support was not significantly associated with OS (HR = 1.13, P = 0.390), death or readmission (OR = 1.18, P = 0.578), time to readmission (HR = 0.92, P = 0.698), or LOS (ß = -0.22, P = 0.726). We identified a potential interaction suggesting cancer type (GI cancer versus other) may be an effect modifier of the relationship between social support and OS (interaction term P = 0.053). In separate unadjusted analyses, limited social support was associated with lower OS (HR = 2.10, P = 0.008) in patients with GI cancer but not other cancer types (HR = 1.00, P = 0.991). CONCLUSION: We used NLP to assess the extent of social support in patients with advanced cancer. We did not identify significant associations of social support with OS or healthcare utilization but found cancer type may be an effect modifier of the relationship between social support and OS. These findings underscore the potential utility of NLP for evaluating social support in patients with advanced cancer.

Single-molecule and in silico dissection of the interaction between Polycomb repressive complex 2 and chromatin.

Polycomb repressive complex 2 (PRC2) installs and spreads repressive histone methylation marks on eukaryotic chromosomes. Because of the key roles that PRC2 plays in development and disease, how this epigenetic machinery interacts with DNA and nucleosomes is of major interest. Nonetheless, the mechanism by which PRC2 engages with native-like chromatin remains incompletely understood. In this work, we employ single-molecule force spectroscopy and molecular dynamics simulations to dissect the behavior of PRC2 on polynucleosome arrays. Our results reveal an unexpectedly diverse repertoire of PRC2 binding configurations on chromatin. Besides reproducing known binding modes in which PRC2 interacts with bare DNA, mononucleosomes, and adjacent nucleosome pairs, our data also provide direct evidence that PRC2 can bridge pairs of distal nucleosomes. In particular, the "1-3" bridging mode, in which PRC2 engages two nucleosomes separated by one spacer nucleosome, is a preferred low-energy configuration. Moreover, we show that the distribution and stability of different PRC2-chromatin interaction modes are modulated by accessory subunits, oncogenic histone mutations, and the methylation state of chromatin. Overall, these findings have implications for the mechanism by which PRC2 spreads histone modifications and compacts chromatin. The experimental and computational platforms developed here provide a framework for understanding the molecular basis of epigenetic maintenance mediated by Polycomb-group proteins.

Relationship Between Longitudinal Coping Strategies and Outcomes in Patients With Acute Myeloid Leukemia.

BACKGROUND: Patients with acute myeloid leukemia (AML) face an abrupt life-threatening illness and experience immense physical and psychological symptoms. However, no data describe how patients with AML cope longitudinally with their illness or the relationship between longitudinal coping and outcomes. METHODS: We conducted a secondary analysis of longitudinal data from 160 patients with high-risk AML enrolled in a supportive care intervention trial to describe coping strategies longitudinally across the illness course. We used the Brief COPE questionnaire, the Hospital Anxiety and Depression Scale, the Post-Traumatic Stress Disorder (PTSD) Checklist-Civilian Version, and the Functional Assessment of Cancer Therapy-Leukemia to measure coping strategies, psychological distress, and quality of life (QoL) at baseline and at weeks 2, 4, 12, and 24 after diagnosis. Electronic health records were used to assess healthcare utilization and end-of-life (EoL) outcomes, and multivariate analyses were used to assess the relationship between coping and outcomes. RESULTS: Longitudinal utilization of approach-oriented coping strategies was significantly associated with less distress (anxiety: ß, -0.18; P<.001; depression symptoms: ß, -0.42; P<.001; PTSD symptoms: ß, -0.60; P<.001) and better QoL (ß, 2.00; P<.001). Longitudinal utilization of avoidant coping strategies was significantly associated with greater distress (anxiety: ß, 0.64; depression symptoms: ß, 0.54; PTSD symptoms: ß, 2.13; P<.001 for all) and worse QoL (ß, -4.27; P<.001). Although the use of approach-oriented and avoidant coping strategies was not significantly associated with hospitalization, chemotherapy administration, or hospice use in the last 30 days of life, approach-oriented coping was associated with lower odds of ICU admissions (odds ratio, 0.92; P=.049). CONCLUSIONS: Longitudinal use of approach-oriented coping strategies was associated with less psychological distress, better QoL, and a lower likelihood of ICU admission, suggesting a possible target for supportive oncology interventions. Coping strategies did not impact EoL outcomes, and further research is needed to elucidate which patient factors impact EoL decision-making.

Clinical Outcomes, Treatment Toxicity, and Health Care Utilization in Older Adults with Aggressive Non-Hodgkin Lymphoma.

BACKGROUND: Although balancing treatment efficacy with risks of complications is critical for older adults with aggressive non-Hodgkin lymphoma (NHL), few studies have described these patients' clinical outcomes, rates of toxicities, and health care utilization. METHODS: We conducted a retrospective analysis of adults ≥65 years diagnosed with aggressive NHL and receiving systemic therapy at Massachusetts General Hospital from April 2000 to July 2020. We abstracted patient characteristics, clinical outcomes, treatment toxicity, unplanned hospitalizations, and intensive care unit (ICU) admissions within 6 months of treatment initiation from the medical record. Using multivariable logistic regression, we examined factors associated with rates of grade 3+ nonhematologic toxicity and unplanned hospitalization. RESULTS: Among 295 patients (median age, 73 years; 39.0% female), 5-year overall survival (OS) was 74.2%. Five-year OS by age group (65-69, 70-74, 75-79, and 80+ years) was 82.2%, 72.0%, 73.6%, and 66.4%, respectively. Overall, 42.4% experienced grade 3+ toxicity, with 8.1% experiencing grades 4-5. The rates of unplanned hospitalization and ICU admission were 41.0% and 6.1%, respectively. In multivariable analysis, hypoalbuminemia (odds ratio [OR], 4.29; p < .001) and high comorbidity score (OR, 4.22; p < .001) were associated with likelihood of grade 3+ toxicity. Hypoalbuminemia (OR, 2.83; p = .003), high comorbidity score (OR, 3.93; p = .001), and receipt of EPOCH (etoposide, prednisone, vincristine, cyclophosphamide, doxorubicin; OR, 5.45; p = .012) were associated with likelihood of unplanned hospitalization. CONCLUSIONS: The majority of older adults receiving upfront therapy for aggressive NHL survive beyond 5 years, yet nearly half experience substantial treatment toxicities and unplanned hospitalizations. Our findings underscore the need for supportive care interventions to enhance the care experience of this population. IMPLICATIONS FOR PRACTICE: The results of this study highlight the potential benefits of intensive chemoimmunotherapy for the majority of older adults with aggressive non-Hodgkin lymphoma, even at advanced ages. Nearly half of older adults experienced substantial treatment toxicities and unplanned hospitalizations, emphasizing the unmet need for supportive care interventions in this population. The present study also identified hypoalbuminemia and patient comorbidity score as factors associated with grade 3+ nonhematologic toxicity and unplanned hospitalization. These findings may guide the development and implementation of targeted supportive care interventions in high-risk older adults with aggressive non-Hodgkin lymphoma.

Clinical Outcomes of Patients Hospitalized with Coronavirus Disease 2019 (COVID-19) in Boston.

BACKGROUND: Outcomes of hospitalized patients with COVID-19 have been described in health systems overwhelmed with a surge of cases. However, studies examining outcomes of patients admitted to hospitals not in crisis are lacking. OBJECTIVE: To describe clinical characteristic and outcomes of all patients with COVID-19 who are admitted to hospitals not in crisis, and factors associated with mortality in this population. DESIGN: A retrospective analysis PARTICIPANTS: In total, 470 consecutive patients with COVID-19 requiring hospitalization in one health system in Boston from January 1, 2020 to April 15, 2020. MAIN MEASURES: We collected clinical outcomes during hospitalization including intensive care unit (ICU) admission, receipt of mechanical ventilation, and vasopressors. We utilized multivariable logistic regression models to examine factors associated with mortality. KEY RESULTS: A total of 470 patients (median age 66 [range 23-98], 54.0% male) were included. The most common comorbidities were diabetes (38.5%, 181/470) and obesity (41.3%, 194/470). On admission, 41.9% (197/470) of patients were febrile and 60.6% (285/470) required supplemental oxygen. During hospitalization, 37.9% (178/470) were admitted to the ICU, 33.6% (158/470) received mechanical ventilation, 29.4% (138/470) received vasopressors, 16.4% (77/470) reported limitations on their desire for life-sustaining therapies such as intubation and cardiopulmonary resuscitation, and 25.1% (118/470) died. Among those admitted to the ICU (N=178), the median number of days on the ventilator was 10 days (IQR 1-29), and 58.4% (104/178) were discharged alive. Older age (OR=1.04, P<0.001), male sex (OR=2.14, P=0.007), higher comorbidities (OR=1.20, P=0.001), higher lactate dehydrogenase on admission (2nd tertile: OR=4.07, P<0.001; 3rd tertile: OR=8.04, P<0.001), and the need for supplemental oxygen on admission (OR=2.17, P=0.014) were all associated with higher mortality. CONCLUSIONS: The majority of hospitalized patients with COVID-19 and those who received mechanical ventilation survived. These data highlight the need to examine public health and system factors that contribute to improved outcomes for this population.

Association of Social Support With Overall Survival and Healthcare Utilization in Patients With Aggressive Hematologic Malignancies.

BACKGROUND: Social support plays a crucial role for patients with aggressive hematologic malignancies as they navigate their illness course. The aim of this study was to examine associations of social support with overall survival (OS) and healthcare utilization in this population. METHODS: A cross-sectional secondary analysis was conducted using data from a prospective longitudinal cohort study of 251 hospitalized patients with aggressive hematologic malignancies at Massachusetts General Hospital from 2014 through 2017. Natural Language Processing (NLP) was used to identify the extent of patients' social support (limited vs adequate as defined by NLP-aided chart review of the electronic health record). Multivariable regression models were used to examine associations of social support with (1) OS, (2) death or readmission within 90 days of discharge from index hospitalization, (3) time to readmission within 90 days, and (4) index hospitalization length of stay. RESULTS: Patients had a median age of 64 years (range, 19-93 years), and most were White (89.6%), male (68.9%), and married (65.3%). A plurality of patients had leukemia (42.2%) followed by lymphoma (37.9%) and myelodysplastic syndrome/myeloproliferative neoplasm (19.9%). Using NLP, we identified that 8.8% (n=22) of patients had limited social support. In multivariable analyses, limited social support was associated with worse OS (hazard ratio, 2.00; P=.042) and a higher likelihood of death or readmission within 90 days of discharge (odds ratio, 3.11; P=.043), but not with time to readmission within 90 days or with index hospitalization length of stay. CONCLUSIONS: In this cohort of hospitalized patients with aggressive hematologic malignancies, we found associations of limited social support with lower OS and a higher likelihood of death or readmission within 90 days of hospital discharge. These findings underscore the utility of NLP for evaluating the extent of social support and the need for larger studies evaluating social support in patients with aggressive hematologic malignancies.

The Emergence of the Tobacco 21 Movement From Needham, Massachusetts, to Throughout the United States (2003-2019).

In February 2003, Needham, Massachusetts, became the first town in the nation to raise the minimum legal sales age for tobacco and nicotine products to 21 years (Tobacco 21). This legislation marked a dramatic departure from existing state and federal laws, which generally set the minimum sales age at 18 years. The Needham law significantly preceded and ultimately heralded the emergence of a nationwide movement to raise such sales age. As of May 2019, 14 states and more than 450 cities and counties have passed legislation raising the minimum legal sales age for tobacco and nicotine products to 21 years, covering more than 30% of the United States' population. The National Academy of Medicine projects that this policy will lower tobacco use rates, particularly among adolescents, and save a substantial number of lives. This narration of the process that led to Needham's passing of Tobacco 21 legislation and to the growth and spread of the Tobacco 21 movement highlights the significant role of public health advocacy and policy in the control of tobacco, the leading preventable cause of disease and death in the United States. (Am J Public Health. 2019;109:1540-1547. doi: 10.2105/AJPH. 2019.305209).