Crystal Structure of an i-Motif from the HRAS Oncogene Promoter.

An i-motif is a non-canonical DNA structure implicated in gene regulation and linked to cancers. The C-rich strand of the HRAS oncogene, 5'-CGCCCGTGCCCTGCGCCCGCAACCCGA-3' (herein referred to as iHRAS), forms an i-motif in vitro but its exact structure was unknown. HRAS is a member of the RAS proto-oncogene family. About 19 % of US cancer patients carry mutations in RAS genes. We solved the structure of iHRAS at 1.77 Šresolution. The structure reveals that iHRAS folds into a double hairpin. The two double hairpins associate in an antiparallel fashion, forming an i-motif dimer capped by two loops on each end and linked by a connecting region. Six C-C+ base pairs form each i-motif core, and the core regions are extended by a G-G base pair and a cytosine stacking. Extensive canonical and non-canonical base pairing and stacking stabilizes the connecting region and loops. The iHRAS structure is the first atomic resolution structure of an i-motif from a human oncogene. This structure sheds light on i-motifs folding and function in the cell.

Predictors of mortality, limb loss, and discharge disposition at admission among patients with necrotizing skin and soft tissue infections.

BACKGROUND: Necrotizing soft tissue infections (NSTI) represent a heterogeneous group of rapidly progressive skin and soft tissue infections associated with significant morbidity and mortality. Efforts to identify factors associated with death have produced mixed results, and little or no data is available for other adverse outcomes. We sought to determine whether admission variables were associated with mortality, limb loss, and discharge disposition in patients with NSTI. METHODS: We analyzed prospectively collected data of adult patients with surgically confirmed NSTI from an NSTI registry maintained at a quaternary referral center. Factors independently associated with mortality, amputation, and skilled nursing facility discharge were identified using logistic regression. RESULTS: Between 2015 and 2018, 446 patients were identified. The median age was 55 years (interquartile range, 43-62). The majority of patients were male (65%), white (77%), and transferred from another facility (90%). The perineum was most commonly involved (37%), followed by the lower extremity (34%). The median number of operative debridements was 3 (interquartile range, 2-4). Overall mortality was 15%, and 21% of extremity NSTI patients required amputation. Age greater than 60 years; creatinine greater than 2 mg/dL; white blood cell count greater than 30 x 10^ /µl, platelets less than 150 × 10/µL, and clostridial involvement were independently associated with greater odds of death; perineal involvement was associated with lower odds of death. Age greater than 60 years; sex, male; nonwhite race; diabetes; chronic wound as etiology; leg involvement; transfer status; and sodium, less than 130 mEq/L were independently associated with amputation. Age greater than 60 years; sex, female; nonwhite race; perineal involvement; and amputation were associated with skilled care facility discharge. CONCLUSION: Necrotizing soft tissue infections are a heterogeneous group of infections involving significantly different patient populations with different outcomes; efforts to differentiate and predict adverse outcomes in NSTI should include laboratory data, comorbidities, infection site, and/or etiology to improve predictions and better account for this heterogeneity. LEVEL OF EVIDENCE: Prognostic, Level III.