Genomics-Guided Discovery of Thailanstatins A, B, and C As Pre-mRNA Splicing Inhibitors and Antiproliferative Agents from Burkholderia thailandensis MSMB43

Abstract

Mining the genome sequence of Burkholderia thailandensis MSMB43 revealed a cryptic biosynthetic gene cluster resembling that of FR901464 (4), a prototype spliceosome inhibitor produced by Pseudomonas sp. No. 2663. Transcriptional analysis revealed a cultivation condition in which a regulatory gene of the cryptic gene cluster is adequately expressed. Consequently, three new compounds, named thailanstatins A (1), B (2) and C (3), were isolated from the fermentation broth of B. thailandensis MSMB43. Thailanstatins are proposed to be biosynthesized by a hybrid polyketide synthase-nonribosomal peptide synthetase pathway. They differ from 4 by lacking an unstable hydroxyl group and by having an extra carboxyl moiety; those differences endow thailanstatins with a significantly greater stability than 4 as tested in phosphate buffer at pH 7.4. In vitro assays showed that thailanstatins inhibit pre-mRNA splicing as potently as 4, with half-maximal inhibitory concentrations in the single to sub µM range. Cell culture assays indicated that thailanstatins also possess potent antiproliferative activities in representative human cancer cell lines, with half-maximal growth inhibitory concentrations in the single nM range. This work provides new chemical entities for research and development, and new structure-activity information for chemical optimization of related spliceosome inhibitors.

Coherence between Cellular Responses and in Vitro Splicing Inhibition for the Anti-tumor Drug Pladienolide B and Its Analogs

“…Corroborating this observation, a recent report provides evidence that changing the epoxide of FD-985 to a cyclopropane does not drastically alter its cytotoxicity but instead appears to stabilize the compound (29). Furthermore, recent papers identified an analog of FR901464, termed spliceostatin B, and two members of the thailanstatin family of natural products that resemble FR901464 and that do not contain the epoxide (35,36). All three compounds are considerably less cytotoxic than their epoxide-containing counterparts.…”

Interchangeable SF3B1 inhibitors interfere with pre-mRNA splicing at multiple stages

“…Structure-activity relationship (SAR) data for the three compounds and related molecules have been steadily emerging (Sakai et al 2002;Mizui et al 2004;Lagisetti et al 2008Lagisetti et al , 2013Lagisetti et al , 2014Albert et al 2009;Fan et al 2011;Gundluru et al 2011;Muller et al 2011;Villa et al 2012Villa et al , 2013Gao et al 2013;Ghosh and Chen 2013;Arai et al 2014;Effenberger et al 2014;Ghosh et al 2014a,b,c;He et al 2014). SSA (1), which is similar to FR901464 (Nakajima et al 1996b), meayamycin (Albert et al 2009), thailanstatins (Liu et al 2013), and sudemycins (Fan et al 2011), differs in structure relative to the other two compounds. PB (2), which is related to E7107 and FD-895 (Kotake et al 2007;Villa et al 2012), and HB (3), a member of GEX1 family (Sakai et al 2002), share a similar side chain, but have different ring structures (macrolide vs. tetrahydropyran).…”

Spliceostatin hemiketal biosynthesis in Burkholderia spp. is catalyzed by an iron/α-ketoglutarate–dependent dioxygenase

“…Harnessing the biosynthetic potential of the producing organisms for compound production and analog generation is an attractive alternative to chemical synthesis. Pladienolide (17) and herboxidiene (18) are biosynthesized by different Streptomyces species via a canonical type I polyketide synthase (PKS) system, whereas biosynthesis of spliceostatins in two Burkholderia strains (FERM BP-3421 and MSMB 43) is encoded by highly homologous, hybrid trans-acyl transferase (AT) PKS-nonribosomal peptide synthetase (NRPS) gene clusters (19,20).…”

“…Subsequently, an analog bearing a terminal carboxylic acid (3) was reported from Burkholderia sp. MSMB 43 (20,24). Although 3 belongs to the same family of compounds as 4 and 5, the name thailanstatin A was used when reporting compound 3, as it had been isolated from a Burkholderia thailandensis-like strain.…”

“…Although 3 belongs to the same family of compounds as 4 and 5, the name thailanstatin A was used when reporting compound 3, as it had been isolated from a Burkholderia thailandensis-like strain. It has recently been shown that strain FERM BP-3421 produces carboxylic acids 1, 2, and 3 in addition to hemiketals 4 and 5 (22,25), whereas only 3 and two chlorohydrin adducts of 3 have been isolated from MSMB 43 (20). We chose to use the term spliceostatin in this manuscript to refer to all congeners 1-5…”