SUMOylation Of GPS2and Its Relative Functional Research

Since identified as a suppressor of JNK pathway, G-protein pathway suppressor2（GPS2） was found invoving many cell proess. GPS2interacts with many transcriptional factor, including p53, papillomavirus E2and RFX4₃v （Regulatory Factor X4variant transcript3）, and participates in transcription regulation. Besides, GPS2involovs in cell cycle regulation, DNA repairs, cytoskeleton architecture, brain development, and metabolism.Resently GPS2was identified as an indispensable component of SMRT （Silencing Mediator for Retinoid and Thyroid-hormone receptors） complex. The SMRT complexes are involved in4-hydroxyl-tamoxifen （4OHT）-mediated gene repression by estrogen receptor alpha （ERa）. Knockdown of GPS2abrogates, while overexpression potentiates, SMRT mediated repression activity. Knockdown of GPS2or SMRT promotes cell proliferation in MCF-7breast cancer cells.As an important post-transcriptional modification, SUMOylation （Small Ubiquition Related Modifier） has a range of effects on its substrates, including alterations in subcellular localization/transport, the protein stability, and changes in their ability to active or repress transcription. Our research focused on the SUMOylation of GPS2and its relative functional regulation.1We showed that GPS2can be modified by SUMO in COS-7cells, which transfected with GPS2and SUMO1, by western blot and immunoprecipitation.2We identified two SUMO attachment site by analysis amino acid sequences and site specific mutant, K45and K71. Substitution of either residue with arginine result in decrease of the inhibition of GPS2as a transcriptional corepressor, suggested that SUMOylation may participates the transcriptional repress mediated by GPS2.3We found that SUMOylation of GPS2promotes the nuclear localization by immunofluorescent assay and nucleo-cytoplasmic separation assay. And the half-life of wild type GPS2was much longer than GPS2mutant2KR. This reason may be that SUMOylation increase the interaction between GPS2and TBL1.4Luciferase reporter assay showed that SUMOylation of GPS2increases the inhibition of ERa indenpent of ligand. The reason maybe that SUMOylation of GPS2promotes the interaction between GPS2and SMRT. And SUMOylation participates in the repress of cell proliferation by GPS2. We conclude that GPS2can be modified by SUMO1, and the modifition increases the nuclear localization and protein stability, promotes the inhibition of ERa and cell proliferation by GPS2.