Marine cyanobacteria are extraordinarily rich in their production of biologically active and structurally unique natural products. A number of these secondary metabolites or their derivatives are lead compounds in drug development programs aimed at providing new therapies to treat cancer, bacterial infections, inflammatory responses and in crop protection to kill harmful microbial pathogens and insects. Isolation and structural analysis of marine and terrestrial cyanobacterial natural products has provided access to an unusually large number of mixed non-ribosomal peptide synthetase/polyketide synthase (NRPS/PKS) systems. The corresponding metabolic systems are comprised of an intriguing set of complex multifunctional proteins that along with allied enzymes generate structurally complex molecules via a modular multi-step process. Over the past several years the Sherman, Gerwick and Smith laboratories have developed a complementary program to clone and characterize the biosynthetic pathways of novel cyanobacterial secondary metabolites that possess significant potential for biotechnological applications. Despite considerable progress, a full understanding of the molecular mechanisms, catalytic activities, kinetic properties, and substrate specificities within cyanobacterial biosynthetic pathways is just beginning to unfold. The proposed research will build upon our accomplishments on the curacin, jamaicamide and cryptophycin/ arenastatin metabolic systems, three robust pathways that have been a rich source of new information. The expected metabolic, biochemical and structural understanding will facilitate the design of new biosynthetic systems that harness the growing potential of cyanobacterial natural product pathways. The full promise of cyanobacterial natural products to yield new lead compounds for development as useful pharmaceuticals will only be realized by closing a series of key gaps in knowledge and technology. Solving these challenges will require development and optimization of genetic and biochemical methods that allow us to 1) manipulate cyanobacterial natural product metabolic systems to produce analog structures, 2) utilize unique secondary metabolite enzymes for creation of novel bioactive molecules and, 3) screen new compounds and analogs to identify promising new anticancer compounds for further development.
The specific aims are: 1. To harness the inherent versatility of cyanobacterial natural product systems to create new anticancer lead compounds. Sub-aims include: a. Investigate ability of cyanobacterial biosynthetic pathways to generate novel analogs using unique laboratory culture and mutasynthesis methodologies. b. Investigate the unique enzymatic capabilities of marine cyanobacterial pathways to engineer new metabolic systems and tailoring processes to generate new bioactive compounds. c. Employ structural biology and site-directed mutagenesis approaches to understand the precise biochemical mechanisms of unique biosynthetic enzymes. d. Develop new chemoenzymatic, in vivo, and in vitro pathways to create new anticancer agents with enhanced medicinal properties 2. Perform bioassays on new compounds resulting from Specific Aim 1. a. New compounds derived from the proposed research will be transferred to Eisai Research Institute and University of Michigan Center for Chemical Genomics for analysis of biological activity using a series of biochemical and cell based assays relevant to cancer.

Public Health Relevance

The proposed research will focus on elucidating the detailed function and mechanistic basis of complex biosynthetic pathways from marine cyanobacteria that create chemically diverse natural products with anti-cancer activity. The ability to understand and subsequently engineer these remarkable biochemical systems will create new opportunities to discover and develop effective drugs for the treatment of human diseases, particularly cancer and related metabolic disorders.

National Institute of Health (NIH)
National Cancer Institute (NCI)
Research Project (R01)
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Synthetic and Biological Chemistry B Study Section (SBCB)
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Fu, Yali
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University of Michigan Ann Arbor
Schools of Pharmacy
Ann Arbor
United States
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Skiba, Meredith A; Bivins, Marissa M; Schultz, John R et al. (2018) Structural Basis of Polyketide Synthase O-Methylation. ACS Chem Biol :
Skiba, Meredith A; Maloney, Finn P; Dan, Qingyun et al. (2018) PKS-NRPS Enzymology and Structural Biology: Considerations in Protein Production. Methods Enzymol 604:45-88
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Skiba, Meredith A; Sikkema, Andrew P; Fiers, William D et al. (2016) Domain Organization and Active Site Architecture of a Polyketide Synthase C-methyltransferase. ACS Chem Biol 11:3319-3327

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