Extrachromosomal circular DNA (eccDNA) has been identified in a broad range of eukaryotes and have been shown to carry genes and regulatory sequences. Additionally, they can amplify within a cell by autonomous replication or reintegration into the genome, effectively influencing copy number in cells. This has significant implications for cancer, where oncogenes are frequently amplified on eccDNA. However, little is known about the exact molecular mechanisms governing eccDNA functionality. To this end, we constructed a fluorescent reporter at an eccDNA-prone locus of the yeast genome, CUP1. It is our hope that this reporter will contribute to a better understanding of eccDNA formation and amplification within a cell.

Polyketides are a wide ranging class of natural microbial products highly relevant to the pharmacological industry. As chemical synthesis of polyketides is quite challenging, significant effort has been made to understand the polyketide synthases (PKSs) responsible for their natural production. Native to Streptomyces, the aln biosynthetic gene cluster was recently characterized and encodes for an iterative type I polyketide synthase (iT1PKS). This iT1PKS produces both , and ,-double bond polyketides named allenomycins; however, the basis in which one bond is chosen over the other is not yet clear. The dehydratase domain, AlnB_DH, is thought to be solely responsible for catalyzing double bond formation. Elucidation of enzyme programming is the first step towards reprogramming AlnB_DH to produce novel industrially relevant products. The Nannenga lab has worked as collaborators to the Zhao lab at the University of Illinois at Urbana-Champaign to unravel AlnB_DH’s structure and mechanism. Here, mutant constructs of AlnB_DH are developed to elucidate enzyme structure and provide insight into active site machinery. The primary focus of this work is on the development of the mutant constructs themselves rather than the methods used for structural or mechanistic determination. Truncated constructs were successfully developed for crystallization and upon x-ray diffraction, a 2.45 Å resolution structure was determined. Point-mutated constructs were then developed based on structural insights, which identified H49, P58, and H62 as critical residues in active site machinery.