SUMO Modification of OsFKBP20-1b Is Integral to Proper Pre-mRNA Splicing upon Heat Stress in Rice.
OsFKBP20-1b, a plant-specific cyclophilin protein, has been implicated to regulate pre-mRNA splicing under stress conditions in rice. Here, we demonstrated that OsFKBP20-1b is SUMOylated in a reconstituted SUMOylation system in E.coli and in planta, and that the SUMOylation-coupled regulation was associated with enhanced protein stability using a less SUMOylated OsFKBP20-1b mutant (5KR_OsFKBP20-1b). Furthermore, OsFKBP20-1b directly interacted with OsSUMO1 and OsSUMO2 in the nucleus and cytoplasm, whereas the less SUMOylated 5KR_OsFKBP20-1b mutant had an impaired interaction with OsSUMO1 and 2 in the cytoplasm but not in the nucleus. Under heat stress, the abundance of an OsFKBP20-1b-GFP fusion protein was substantially increased in the nuclear speckles and cytoplasmic foci, whereas the heat-responsiveness was remarkably diminished in the presence of the less SUMOylated 5KR_OsFKBP20-1b-GFP mutant. The accumulation of endogenous SUMOylated OsFKBP20-1b was enhanced by heat stress in planta. Moreover, 5KR_OsFKBP20-1b was not sufficiently associated with the U&nbsp;snRNAs in the nucleus as a spliceosome component. A protoplast transfection assay indicated that the low SUMOylation level of 5KR_OsFKBP20-1b led to inaccurate alternative splicing and transcription under heat stress. Thus, our results suggest that OsFKBP20-1b is post-translationally regulated by SUMOylation, and the modification is crucial for proper RNA processing in response to heat stress in rice.
['Park|Hyun-Ji|HJ|', 'Jung|Hae-Myeong|HM|0000-0003-4914-610X', 'Lee|Areum|A|0000-0001-7610-2773', 'Jo|Seung-Hee|SH|', 'Lee|Hyo-Jun|HJ|', 'Kim|Hyun-Soon|HS|', 'Jung|Choon-Kyun|CK|0000-0001-5643-309X', 'Min|Sung-Ran|SR|', 'Cho|Hye-Sun|HS|0000-0003-0469-7186']
D004926:Escherichia coli D018869:Heat-Shock Response D012275:Oryza D010940:Plant Proteins D012326:RNA Splicing D058207:Sumoylation
OsFKBP20-1b pre-mRNA splicing heat stress SUMOylation splicing factor