Rhodoxanthin synthase from honeysuckle; a membrane diiron enzyme catalyzes the multistep conversation of ß-carotene to rhodoxanthin.

Rhodoxanthin is a vibrant red carotenoid found across the plant kingdom and in certain birds and fish. It is a member of the atypical retro class of carotenoids, which contain an additional double bond and a concerted shift of the conjugated double bonds relative to the more widely occurring carotenoid pigments, and whose biosynthetic origins have long remained elusive. Here, we identify LHRS (Lonicera hydroxylase rhodoxanthin synthase), a variant ß-carotene hydroxylase (BCH)-type integral membrane diiron enzyme that mediates the conversion of ß-carotene into rhodoxanthin. We identify residues that are critical to rhodoxanthin formation by LHRS. Substitution of only three residues converts a typical BCH into a multifunctional enzyme that mediates a multistep pathway from ß-carotene to rhodoxanthin via a series of distinct oxidation steps in which the product of each step becomes the substrate for the next catalytic cycle. We propose a biosynthetic pathway from ß-carotene to rhodoxanthin.

Versatile genetic assembly system (VEGAS) to assemble pathways for expression in S. cerevisiae.

We have developed a method for assembling genetic pathways for expression in Saccharomyces cerevisiae. Our pathway assembly method, called VEGAS (Versatile genetic assembly system), exploits the native capacity of S. cerevisiae to perform homologous recombination and efficiently join sequences with terminal homology. In the VEGAS workflow, terminal homology between adjacent pathway genes and the assembly vector is encoded by 'VEGAS adapter' (VA) sequences, which are orthogonal in sequence with respect to the yeast genome. Prior to pathway assembly by VEGAS in S. cerevisiae, each gene is assigned an appropriate pair of VAs and assembled using a previously described technique called yeast Golden Gate (yGG). Here we describe the application of yGG specifically to building transcription units for VEGAS assembly as well as the VEGAS methodology. We demonstrate the assembly of four-, five- and six-gene pathways by VEGAS to generate S. cerevisiae cells synthesizing ß-carotene and violacein. Moreover, we demonstrate the capacity of yGG coupled to VEGAS for combinatorial assembly.

Defining an acceptable period of time from melanoma biopsy to excision.

Melanoma is the most lethal form of skin cancer and it is the second most common cancer among adolescents and young adults. The aim of this work is to determine if surgical intervals differ between four different clinics and between departments within the hospitals, and to compare these to industry standards. Surgical intervals were measured through retrospective chart review at four dermatology clinics. Of 205 melanoma cases, clinic and departmental median surgical intervals ranged 15-36.5 days and 26-48 days, respectively. There was significant association between clinic and time between biopsy and pathology report, time between pathology report and excision, and total surgical interval (P<0.0001, P=0.03, and P<0.0001 respectively). There was significant association between department and time between pathology report and excision, and surgical interval (P<0.0001, and P=0.003 respectively). Pair-wise comparisons detected significantly longer intervals between some clinics and departments (maximum difference 67.3%, P<0.0001). Hypothesis-based, informal guidelines recommend treatment within 4-6 weeks. In this study, median surgical intervals varied significantly between clinics and departments, but nearly all were within a 6-week frame.

Integrating transcriptional and metabolite profiles to direct the engineering of lovastatin-producing fungal strains.

We describe a method to decipher the complex inter-relationships between metabolite production trends and gene expression events, and show how information gleaned from such studies can be applied to yield improved production strains. Genomic fragment microarrays were constructed for the Aspergillus terreus genome, and transcriptional profiles were generated from strains engineered to produce varying amounts of the medically significant natural product lovastatin. Metabolite detection methods were employed to quantify the polyketide-derived secondary metabolites lovastatin and (+)-geodin in broths from fermentations of the same strains. Association analysis of the resulting transcriptional and metabolic data sets provides mechanistic insight into the genetic and physiological control of lovastatin and (+)-geodin biosynthesis, and identifies novel components involved in the production of (+)-geodin, as well as other secondary metabolites. Furthermore, this analysis identifies specific tools, including promoters for reporter-based selection systems, that we employed to improve lovastatin production by A. terreus.