The first crystal structures of hybrid and parallel four-tetrad intramolecular G-quadruplexes.

G-quadruplexes (GQs) are non-canonical DNA structures composed of stacks of stabilized G-tetrads. GQs play an important role in a variety of biological processes and may form at telomeres and oncogene promoters among other genomic locations. Here, we investigate nine variants of telomeric DNA from Tetrahymena thermophila with the repeat (TTGGGG)n. Biophysical data indicate that the sequences fold into stable four-tetrad GQs which adopt multiple conformations according to native PAGE. Excitingly, we solved the crystal structure of two variants, TET25 and TET26. The two variants differ by the presence of a 3'-T yet adopt different GQ conformations. TET25 forms a hybrid [3 + 1] GQ and exhibits a rare 5'-top snapback feature. Consequently, TET25 contains four loops: three lateral (TT, TT, and GTT) and one propeller (TT). TET26 folds into a parallel GQ with three TT propeller loops. To the best of our knowledge, TET25 and TET26 are the first reported hybrid and parallel four-tetrad unimolecular GQ structures. The results presented here expand the repertoire of available GQ structures and provide insight into the intricacy and plasticity of the 3D architecture adopted by telomeric repeats from T. thermophila and GQs in general.

Implementation of a Pediatric Population Health Asthma Program in Academic Medical Center-Affiliated Urban and Suburban Practices.

A tiered pediatric Asthma Population Health Management Program (APHMP), based on evidence-based practices, that differentially targets populations for intervention based on rising risk for high utilization and disease complications was implemented at 6 urban and suburban practices affiliated with an academic medical center. In addition to standard pediatric asthma care, APHMP adds regular administration of the asthma control test (ACT), provider education on performance variation, and monitoring through the electronic health record-based asthma registry. As patients' use of acute health care services and complications increases, APHMP integrates multidisciplinary interventions, including an asthma coach who conducts environmental assessments in addition to addressing social needs, into their primary care. A retrospective cohort study method was used to assess population-level effects on asthma event rates and practice- and provider-level variation from 2017 to 2019. Consistent with well-documented health disparities in pediatric asthma, the analysis demonstrated that patients who were male (odds ratio [OR] = 1.21, 95% confidence interval [CI] = 1.02-1.43), 4-8 years old (OR = 4.91, 95% CI = 3.27-7.37), Spanish speaking (OR = 1.67, 95% CI = 1.54-1.81), from low-income neighborhoods (OR = 1.56, 95% CI = 1.53-2.46), and with ACT <20 (OR = 2.88, 95% CI = 1.97-4.21) had higher odds of having asthma events. Six percent of patients studied were found to be at risk for high health care utilization and disease complications. Study limitations include the absence of a control group, the mixed model data collection approach, and the effects of seasonal variation on asthma events. Future directions include analyzing disease management program outcomes of incorporating an asthma coach into a patient's primary care team and addressing provider-level variation in asthma event rates.

N-methyl mesoporphyrin IX as a highly selective light-up probe for G-quadruplex DNA.

N-methyl mesoporphyrin IX (NMM) is a water-soluble, non-symmetric porphyrin with excellent optical properties and unparalleled selectivity for G-quadruplex (GQ) DNA. G-quadruplexes are non-canonical DNA structures formed by guanine-rich sequences. They are implicated in genomic stability, longevity, and cancer. The ability of NMM to selectively recognize GQ structures makes it a valuable scaffold for designing novel GQ binders. In this review, we survey the literature describing the GQ-binding properties of NMM as well as its wide utility in chemistry and biology. We start with the discovery of the GQ-binding properties of NMM and the development of NMM-binding aptamers. We then discuss the optical properties of NMM, focusing on the light-switch effect - high fluorescence of NMM induced upon its binding to GQ DNA. Additionally, we examine the affinity and selectivity of NMM for GQs, as well as its ability to stabilize GQ structures and favor parallel GQ conformations. Furthermore, a portion of the review is dedicated to the applications of NMM-GQ complexes as biosensors for heavy metals, small molecules (e.g. ATP and pesticides), DNA, and proteins. Finally and importantly, we discuss the utility of NMM as a probe to investigate the roles of GQs in biological processes.