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Absolute configuration of brevisamide and brevisin: confirmation of a universal biosynthetic process for Karenia brevis polyethers.

ABSTRACT: The discovery of brevisin, the first example of an "interrupted" polycyclic ether, obtained from the dinoflagellate Karenia brevis, posed some important questions regarding the mechanism of the cyclization process. Consequently, we have established absolute configurations of brevisin and its related metabolite brevisamide using a modified Mosher's esterification method. For brevisin, analysis was carried out on both the 31-monokis- and the 10,31-bis-MTPA esters. The results suggest that both metabolites, like other polyethers from K. brevis, result from polyepoxide precursors with uniform (S, S) configurations for all epoxides and provide further support for a universal stereochemical model for dinoflagellate polyether formation.

SUBMITTER: Van Wagoner RM

PROVIDER: S-EPMC2925417 | biostudies-literature | 2010 Jun

REPOSITORIES: biostudies-literature

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Absolute configuration of brevisamide and brevisin: confirmation of a universal biosynthetic process for Karenia brevis polyethers.

Van Wagoner Ryan M RM Satake Masayuki M Bourdelais Andrea J AJ Baden Daniel G DG Wright Jeffrey L C JL

Journal of natural products 20100601 6

The discovery of brevisin, the first example of an "interrupted" polycyclic ether, obtained from the dinoflagellate Karenia brevis, posed some important questions regarding the mechanism of the cyclization process. Consequently, we have established absolute configurations of brevisin and its related metabolite brevisamide using a modified Mosher's esterification method. For brevisin, analysis was carried out on both the 31-monokis- and the 10,31-bis-MTPA esters. The results suggest that both met ...[more]

PMID: 20527743

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Project description:Dinoflagellates possess many physiological processes that appear to be under post-transcriptional control. However, the extent to which their genes are regulated post-transcriptionally remains unresolved. To gain insight into role of de novo transcription in dinoflagellates, we biosynthetically labeled RNA with 4-thiouracil to isolate newly transcribed RNA in Karenia brevis. These isolated fractions were then used for analysis of global de novo transcription by hybridization to a K. brevis microarray. As previous microarray studies indicated that transcripts for pentatricopeptide repeat (PPR) proteins rapidly increased in response to nutrient addition, we queried the newly synthesized RNA pools at 1 and 4 h following nitrate addition to N-depleted cultures. Transcriptome-wide there was little evidence of changes in the rate of de novo transcription during the first 4 h, relative to that in N-depleted cells, and no evidence for increased PPR protein transcription. These results lend support to the growing consensus of post-transcriptional control of gene expression in dinoflagellates.M-bM-^@M-^C Cultures were acclimated to 10 M-BM-5M nitrate for a minimum of two months during which time cultures were transferred weekly in log phase. For addition experiments, nutrient replete and N-limited 1 L cultures were grown to stationary phase (Day 9). Using sodium nitrate, 155 M-BM-5M NO3 was added to stationary phase cultures. Cultures were exposed to 0.2 mM 4-thiouracil for 1 h to biosynthetically label newly transcribed RNA during the first hour post-N-addition (n=3) or during the fourth hour post-N-addition (n=3). N-limited cultures (n=3) were also exposed to 0.2 mM 4-thiouracil for 1 h to biosynthetically label newly transcribed RNA. Cultures were harvested after 1 h exposure to 4-thiouracil and total RNA extracted. Following extraction, RNA was biotinylated to allow for purification of the thiolated newly synthesized RNA from the total RNA pool using streptavidin coated magnetic beads. The newly transcribed RNA from each culture was independently labeled and hybridized to microarrys in a one color format. Based on the appearance of bioanlayzer profiles newly synthesized RNA was treated as mRNA in the labeling protocol.

Project description:Dinoflagellates possess many physiological processes that appear to be under post-transcriptional control. However, the extent to which their genes are regulated post-transcriptionally remains unresolved. To gain insight into the role of differential mRNA stability in dinoflagellates, we biosynthetically labeled RNA with 4-thiouracil to isolate newly transcribed and pre-existing RNA pools in Karenia brevis. These isolated fractions were then used for analysis of global mRNA stability by hybridization to a K. brevis microarray. Global K. brevis mRNA half-lives were calculated from the ratio of newly transcribed/pre-existing RNA for 7086 array features using the online software HALO (Half-life Organizer). Overall, mRNA half-lives were substantially longer than reported in other organisms studied at the global level, ranging from 42 minutes to greater than 3 days, with a median of 33 hours. Thirteen percent of messages showed a half-life of 3 days, demonstrating their stability throughtout the course of the cell cycle and divison. Consistent with well-documented trends observed in other organisms, housekeeping processes, including energy metabolism and transport, were significantly enriched in the most highly stable messages. Shorter-lived transcripts included a higher proportion of transcriptional regulation, stress response, and other response/regulatory processes. Log phase cultures (n=6) were exposed to 0.2 mM 4-thiouracil for 2h to biosynthetically label newly transcribed RNA and total RNA was extracted. Following extraction, RNA was biotinylated to allow for purification of the thiolated newly synthesized RNA from the total RNA pool using streptavidin coated magnetic beads. From each replicate 3 pools of RNA, total RNA, pre-exisiting RNA, and newly synthesized RNA, were Cy3 labeled and hybridized to microarrys in a one color format. Based on the appearance of bioanlayzer profiles, total and pre-existing RNA were treated as total RNA, while newly synthesized RNA was treated as mRNA in the labeling protocol.

Dataset Information

Absolute configuration of brevisamide and brevisin: confirmation of a universal biosynthetic process for Karenia brevis polyethers.

Publications

Absolute configuration of brevisamide and brevisin: confirmation of a universal biosynthetic process for Karenia brevis polyethers.

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