We have identified the plant biflavonoid hinokiflavone as an inhibitor of splicing in vitro and modulator of alternative splicing in cells. Chemical synthesis confirms hinokiflavone is the active molecule. Hinokiflavone inhibits splicing in vitro by blocking spliceosome assembly, leading to accumulation of the A complex. Cells treated with hinokiflavone show altered subnuclear organization specifically of splicing factors required for A complex formation, which relocalize together with SUMO1 and SUMO2 into enlarged nuclear speckles. Hinokiflavone increases protein SUMOylation levels, both in in vitro splicing reactions and in cells. Hinokiflavone also inhibited a purified, E. coli expressed SUMO protease, SENP1, in vitro, indicating the increase in SUMOylated proteins results primarily from inhibition of de-SUMOylation. Using a quantitative proteomics assay we identified many SUMO2 sites whose levels increased in cells following hinokiflavone treatment, with the major targets including 6 proteins that are components of the U2 snRNP and required for A complex formation.
- Angus I Lamond
- Angus I Lamond
- Ronald T Hay
- Ronald T Hay
- Triin Tammsalu
- Lewis J King
- Helmi Kreinin
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
- Juan Valcárcel, Centre de Regulació Genòmica (CRG), Barcelona, Spain
© 2017, Pawellek et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
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