Abstract. We studied the mechanism by which the para and meta positional isomers of nitric oxide-donating aspirin (NO-ASA) inhibit human colon cancer cell growth. These compounds are promising chemopreventive agents and represent a broader class of novel drugs. The two isomers differ drastically in their 24-h IC 50 s for cell growth, which are 12 μM for p-NO-ASA and 230 μM for m-NO-ASA. We examined their effects on cell signaling cascades, including predominantly the mitogen activated protein kinases (MAPKs). The principal differences between the two isomers were: a) p-NO-ASA exerts its effect earlier than m-NO-ASA; b) the predominant effect of m-NO-ASA is on ERK1/2 and Akt; whereas that of p-NO-ASA is on JNK1/2, while both activate p38, with p-NO-ASA showing a stronger and earlier effect; c) ATF-2 is more responsive to m-NO-ASA and c-Jun to p-NO-ASA; d) both isomers seem to have similar effects on AP-1 binding, the main difference between them being the timing of the effect; p-NO-ASA's effect is early and m-NO-ASA's is late; e) p-NO-ASA has an earlier and stronger effect on p21, while m-NO-ASA's effect occurs later and is weaker; and f) cell cycle changes follow the effect on p21 expression. Our findings underscore the role of positional isomerism in modulating the pharmacological effects of drugs and have potentially important implications for the further development of these chemoprevention agents.

Approximately one disruption in DNA replication occur every cell cycle in bacteria leading to partially duplicated chromosomes. Since unfinished replication can result in genome instability and cell death, bacteria need a mechanism to reload the replication machinery onto the genome. Known as the replication restart primosome (RRP), several proteins function to reload the replicative helicase onto abandoned replication forks, restarting DNA replication. PriA is the most conserved member of the RRP, initiating the dominant replication restart pathway. A helicase, PriA remodels collapsed forks and serves as a platform for binding of other primosomal proteins. The Madison West High School Students Modeling a Research Topic (SMART) Team modeled PriA using 3D printing technology. PriA is a multi‐domain protein and residues important for DNA binding, ATP hydrolysis, and helicase activity are modeled. Since DNA replication restart pathways are essential in preserving genomic integrity and cell viability in bacteria, studies of PriA offer an approach to developing novel antibacterial compounds. Supported by a grant from NIH‐CTSA.

The treatment of bacterial diseases has become a serious problem in clinical medicine in large part because of antibiotic resistance. One way bacteria have increased resistance to drugs is the overexpression of multidrug efflux pumps, exemplified by AcrAB‐TolC, a group of three proteins that span both the inner and outer membranes of E. coli. AcrAB‐TolC transports a wide range of foreign compounds and a broad spectrum of antibiotics. AcrB forms a homo‐trimeric structure that uses cyclical conformational changes powered by ATP to transport foreign compounds into the TolC pore which eventually expels the compounds from the bacteria. The role of AcrA is less defined, perhaps providing structural support to AcrB. The Madison West High School SMART Team (Students Modeling A Research Topic) modeled the interactions between AcrB and associated proteins in the E. coli pump using 3D printing technology to further study the mechanisms of bacterial drug efflux, as well as gain a better understanding of other drug efflux transport mechanisms, such as that used by P‐glycoprotein, which is important in cancer biology and human resistance to chemotherapeutics. The study of the detailed structures of AcrAB‐TolC may be of paramount importance in the development of novel pharmaceuticals against bacterial infections. Supported by grants from NIH‐SEPA and NIH‐CTSA.

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DNA replication is a vital process in all organisms and understanding the fundamental biochemical interactions that drive replication is essential. Single‐stranded DNA‐binding (SSB) proteins form an important component of the replication machinery that facilitates the transfer of RNA primers from the enzyme primase to the replicative polymerase. This activity occurs throughout lagging‐strand DNA replication. The crystal structure of the E. coli χψ subunit of the DNA polymerase III holoenzyme bound to its interaction site on SSB has been determined. The Madison West High School Students Modeling a Research Topic (SMART) Team, in collaboration with the Milwaukee School of Engineering, has modeled this interaction using 3D Rapid Prototyping Technology to gain insights into the physical interactions that drive DNA replication. The SMART team program allows students to experience the scientific process beyond the textbook by investigating the experimental methodology of structural biology and takes students out of the classroom and into the laboratory. Supported by grants from the Howard Hughes Medical Institute and NIH‐NCRR‐SEPA.