ϕX174 Procapsid Assembly: Effects of an Inhibitory External Scaffolding Protein and Resistant Coat Proteins In Vitro.

During ϕX174 morphogenesis, 240 copies of the external scaffolding protein D organize 12 pentameric assembly intermediates into procapsids, a reaction reconstituted in vitro In previous studies, ϕX174 strains resistant to exogenously expressed dominant lethal D genes were experimentally evolved. Resistance was achieved by the stepwise acquisition of coat protein mutations. Once resistance was established, a stimulatory D protein mutation that greatly increased strain fitness arose. In this study, in vitro biophysical and biochemical methods were utilized to elucidate the mechanistic details and evolutionary trade-offs created by the resistance mutations. The kinetics of procapsid formation was analyzed in vitro using wild-type, inhibitory, and experimentally evolved coat and scaffolding proteins. Our data suggest that viral fitness is correlated with in vitro assembly kinetics and demonstrate that in vivo experimental evolution can be analyzed within an in vitro biophysical context. IMPORTANCE: Experimental evolution is an extremely valuable tool. Comparisons between ancestral and evolved genotypes suggest hypotheses regarding adaptive mechanisms. However, it is not always possible to rigorously test these hypotheses in vivo We applied in vitro biophysical and biochemical methods to elucidate the mechanistic details that allowed an experimentally evolved virus to become resistant to an antiviral protein and then evolve a productive use for that protein. Moreover, our results indicate that the respective roles of scaffolding and coat proteins may have been redistributed during the evolution of a two-scaffolding-protein system. In one-scaffolding-protein virus assembly systems, coat proteins promiscuously interact to form heterogeneous aberrant structures in the absence of scaffolding proteins. Thus, the scaffolding protein controls fidelity. During ϕX174 assembly, the external scaffolding protein acts like a coat protein, self-associating into large aberrant spherical structures in the absence of coat protein, whereas the coat protein appears to control fidelity.

Educational Outcomes of a 4-Year MD-MPH Dual-Degree Program: High Completion Rates and Higher Likelihood of Primary Care Residency.

PURPOSE: In 2007, University of Texas Health Science Center Houston School of Public Health at San Antonio (UTHealth SPH) and UT Health San Antonio Long School of Medicine (LSOM) designed and implemented a 4-year dual MD and Master of Public Health (MPH) program. Dual MD-MPH programs wherein students can receive both degrees within 4 years are unique, and programmatic evaluation may have generalizable implications for accredited MD-MPH programs. METHOD: Demographic information was collected from UTHealth SPH and LSOM student data. The primary outcome variable was MD-MPH program completion in 4 years. Comprehensive Basic Science Examination (CBSE) scores, United States Medical Licensing Examination Step 1 and Step 2 scores, and successful primary care residency match data were compared between MD-MPH and MD-only students. Family medicine, internal medicine, obstetrics-gynecology, and pediatrics were considered primary care residencies, and an analysis excluding obstetrics-gynecology was also conducted. RESULTS: Of 241 MD-MPH students enrolled 2007-2017, 66% were women, 22% Hispanic, and 10% African American. Four-year MD-MPH program completion occurred for 202 (93% of eligible) students; 9 (4.1%) received MD only, 3 (1.4%) received MPH only; and 4 (1.8%) received neither. MD-MPH students' median CBSE score was 2 points lower than for MD-only students (P = .035), but Step 1 and 2 scores did not differ. Primary care residency match was more likely compared with MD-only students, both including and excluding obstetrics-gynecology (odds ratio [OR]: 1.75; 95% confidence interval [CI]: 1.31, 2.33; and OR: 1.36; 95% CI: 1.02, 1.82, respectively). CONCLUSIONS: The 4-year MD-MPH program retains and graduates a socioeconomically and racial/ethnically diverse group of students with a 93% success rate. MD-MPH graduates were more likely to pursue primary care residency than non-dual-degree students, which may have implications for addressing population health disparities.