Samantha Tucker-Samaras

Antisense-Guided Isolation and Structure Elucidation of Pannomycin, a Substituted cis-Decalin from Geomyces pannorum

Antisense-based screening strategies can be used to sensitize a microorganism and selectively detect inhibitors against a particular cellular target of interest. A strain of Staphylococcus aureus that generates an antisense RNA against SecA,a central member of the protein secretion machinery, has been used to screen for novel antibacterials. Possible inhibitors of the SecA ATP-ase were selected with a high-throughput, two-plate agar-based whole cell differential sensitivity screen. After screening a library of over 115 000 natural products extracts with the SecA antisense strain, an extract of Geomyces pannorum was identified as providing increased activity against the sensitized strain as compared with the wild-type control. Bioassay-guided isolation of the active component from this fungal extract provided a new cis-decalin secondary metabolite, which we have named pannomycin.

Metabolic signature of sun exposed skin suggests catabolic pathway overweighs anabolic pathway.

Skin chronically exposed to sun results in phenotypic changes referred as photoaging. This aspect of aging has been studied extensively through genomic and proteomic tools. Metabolites, the end product are generated as a result of biochemical reactions are often studied as a culmination of complex interplay of gene and protein expression. In this study, we focused exclusively on the metabolome to study effects from sun-exposed and sun-protected skin sites from 25 human subjects. We generated a highly accurate metabolomic signature for the skin that is exposed to sun. Biochemical pathway analysis from this data set showed that sun-exposed skin resides under high oxidative stress and the chains of reactions to produce these metabolites are inclined toward catabolism rather than anabolism. These catabolic activities persuade the skin cells to generate metabolites through the salvage pathway instead of de novo synthesis pathways. Metabolomic profile suggests catabolic pathways and reactive oxygen species operate in a feed forward fashion to alter the biology of sun exposed skin.

Regulation of DNA Repair Process by the Pro-Inflammatory NF-κB Pathway

Skin is the largest organ of the body. It is organized into three main layers, epidermis, der‐ mis and subcutaneous layer. The epidermis, an outermost avascular layer, is formed by ker‐ atinocytes at the epidermal basal layer that differentiate into corneocytes at the outer layer of the epidermis. The dermis lies below the epidermis separated by a basement membrane and is composed mainly of fibroblasts. The primary function of skin is to constitute an effi‐ cient barrier to protect the organism both from water evaporation and from external aggres‐ sions. Skin is an excellent organ system to study DNA damage and repair since skin is routinely exposed to external and internal aggressors which can induce DNA damage. Sun‐ light is the primary environmental inducer of damage in the skin. In particular ultraviolet radiations (UVR) are known to induce damage on DNA bases by direct absorption of pho‐ tons. Typical damages from the direct effect of UVR are the cyclobutane pyrimidine dimers (CPD) or the 6-4 photoproducts formation both created by dimerization of contiguous pyri‐ midines on the DNA [1]. Sunlight also induces significant damage to skin cells through the generation of Reactive Oxygen Species (ROS) which damage DNA nucleobases and the sug‐ ar phosphate backbone. Depending on the attacking ROS (singlet oxygen and hydroxyl radi‐ cals through the formation of superoxide radicals), different modifications are generated to DNA such as bulky (8-oxoguanosine, as guanine is the most easily oxidized base, thymi‐ dine and cytosine glycol) and non bulky (cyclo purine and etheno adducts) base modifica‐ tions, spontaneous hydrolysis of a normal or damaged nucleobase leading to an abasic site, (See review [2]). Finally ROS may also generate other forms of DNA damage such as single strand breaks (SSB) or double strand breaks (DSB) when the free radical attack is located on the polydeoxyribose chain. Other external aggressors, such as cigarette smoke and pollu‐

4‐Hexyl‐1,3‐phenylenediol, a nuclear factor‐κB inhibitor, improves photodamaged skin and clinical signs of ageing in a double‐blinded, randomized controlled trial

The nuclear factor‐κB (NF‐κB) pathway is a key mediator of inflammation; however, few studies have examined the direct effects of NF‐κB inhibition on the skin.