Rational Design of Polyketide Natural Products

Compounds of polyketide origin possess a wealth of pharmacological effects, including antibacterial, antifungal, antiparasitic, anticancer and immunosuppressive activities. Many of these compounds and their semi-synthetic derivatives are used today in the clinic. The first complete gene cluster encoding the polyketide antibiotic actinorhodin was cloned twenty years ago. The erythromycin gene cluster followed in 1990, and since then most of the gene clusters encoding commercially important drugs have also been cloned, sequenced and their biosynthetic mechanisms studied in great detail. Recent advances in the area of biosynthetic engineering of the enzymes involved in polyketide biosynthesis are presented in this review. The biosynthesis of a typical polyketide can be divided into three separate steps, including (i) choice of starter unit, (ii) the choice of extender units and the degree of beta-keto group reduction, and (iii) post-PKS tailoring of the basic polyketide backbone. Each of these steps represents a potential opportunity for the introduction of structural modification. The technologies to achieve this have now been highly developed and transferred into the industrial arena. The power of biosynthetic engineering will be exemplified by manipulations carried out on the erythromycin and the rapamycin biosynthetic gene clusters

Personalization matters:the effect of sex in multivitamin-multimineral-based cancer prevention

The prevention of non-communicable diseases like cancer contributes to healthy aging. Dietary supplements might support such prevention; their effect likely depends on the personal characteristics of the individuals receiving them. To evaluate the influence of sex on reducing cancer incidence with multivitamin-multimineral (MVM) supplementation, sex-specific results of the efficacy of MVM supplementation for cancer prevention were collected and meta-analyzed (using fixed effect (FE) and random effect (RE) models). Three trials included in the “US Preventive Services Task Force Recommendation Statement Report regarding Vitamin, Mineral, and Multivitamin Supplementation to Prevent Cardiovascular Disease and Cancer” were used, namely, COSMOS, SU.VI.MAX, and PHS2. A total of 28,558 men and 20,542 women were included. Multivitamin-multimineral supplementation significantly reduced cancer incidence in the entire population (HR 0.93 [95% CI, 0.88–0.99], FE and RE); sex-specific meta-analysis showed beneficial effects of supplementation in men (HR 0.91 [95% CI, 0.85–0.97] (FE)/0.88 [95% CI, 0.77–1.01] (RE)); however, there was no effect in women (HR 1.00 [95% CI, 0.88–1.14], FR and RE); (P difference = 0.17). Sex could influence the effect of MVM supplementation in reducing cancer incidence, with supplementation being effective only in male individuals. These results might be informative for future research and public health policy makers.</p

FK506 biosynthesis is regulated by two positive regulatory elements in <it>Streptomyces tsukubaensis</it>

<p>Abstract</p> <p>Background</p> <p>FK506 (Tacrolimus) is an important immunosuppressant, produced by industrial biosynthetic processes using various <it>Streptomyces</it> species. Considering the complex structure of FK506, it is reasonable to expect complex regulatory networks controlling its biosynthesis. Regulatory elements, present in gene clusters can have a profound influence on the final yield of target product and can play an important role in development of industrial bioprocesses.</p> <p>Results</p> <p>Three putative regulatory elements, namely <it>fkbR</it>, belonging to the LysR-type family, <it>fkbN</it>, a large ATP-binding regulator of the LuxR family (LAL-type) and <it>allN</it>, a homologue of AsnC family regulatory proteins, were identified in the FK506 gene cluster from <it>Streptomyces tsukubaensis</it> NRRL 18488, a progenitor of industrial strains used for production of FK506. Inactivation of <it>fkbN</it> caused a complete disruption of FK506 biosynthesis, while inactivation of <it>fkbR</it> resulted in about 80% reduction of FK506 yield. No functional role in the regulation of the FK506 gene cluster has been observed for the <it>allN</it> gene. Using RT-PCR and a reporter system based on a chalcone synthase <it>rppA</it>, we demonstrated, that in the wild type as well as in <it>fkbN</it>- and <it>fkbR</it>-inactivated strains, <it>fkbR</it> is transcribed in all stages of cultivation, even before the onset of FK506 production, whereas <it>fkbN</it> expression is initiated approximately with the initiation of FK506 production. Surprisingly, inactivation of <it>fkbN</it> (or <it>fkbR</it>) does not abolish the transcription of the genes in the FK506 gene cluster in general, but may reduce expression of some of the tested biosynthetic genes. Finally, introduction of a second copy of the <it>fkbR</it> or <it>fkbN</it> genes under the control of the strong <it>ermE</it>* promoter into the wild type strain resulted in 30% and 55% of yield improvement, respectively.</p> <p>Conclusions</p> <p>Our results clearly demonstrate the positive regulatory role of <it>fkbR</it> and <it>fkbN</it> genes in FK506 biosynthesis in <it>S. tsukubaensis</it> NRRL 18488. We have shown that regulatory mechanisms can differ substantially from other, even apparently closely similar FK506-producing strains, reported in literature. Finally, we have demonstrated the potential of these genetically modified strains of <it>S. tsukubaensis</it> for improving the yield of fermentative processes for production of FK506.</p