Genomics-Guided
Discovery of Thailanstatins A, B, and C As Pre-mRNA Splicing Inhibitors
and Antiproliferative Agents from <i>Burkholderia thailandensis</i> MSMB43
- Publication date
- Publisher
Abstract
Mining the genome sequence of <i>Burkholderia thailandensis</i> MSMB43 revealed a cryptic biosynthetic
gene cluster resembling that
of FR901464 (<b>4</b>), a prototype spliceosome inhibitor produced
by <i>Pseudomonas</i> 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 (<b>1</b>), B (<b>2</b>), and C (<b>3</b>), were isolated from the fermentation broth
of <i>B. thailandensis</i> MSMB43. Thailanstatins are proposed
to be biosynthesized by a hybrid polyketide synthase–nonribosomal
peptide synthetase pathway. They differ from <b>4</b> by lacking
an unstable hydroxyl group and by having an extra carboxyl moiety;
those differences endow thailanstatins with a significantly greater
stability than <b>4</b> as tested in phosphate buffer at pH
7.4. <i>In vitro</i> assays showed that thailanstatins inhibit
pre-mRNA splicing as potently as <b>4</b>, 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