Sumoylation of specificity protein 1 augments its degradation by changing the localization and increasing the specificity protein 1 proteolytic process.
Although specificity protein 1 (Sp1) accumulation has been found in various tumor strains, its mechanism is still not very clear. Herein, we found that modification of Sp1 by SUMO-1 facilitates Sp1 degradation. Our findings revealed that, although the amounts of Sp1 and Sp1 mutant (K16R) [Sp1(K16R)] mRNA in cells were equal, the protein level of Sp1(K16R) was higher than that of wild-type Sp1. We also proved that this sumoylation site was not the residue at which ubiquitination occurred. Invitro and in vivo pull-down assays revealed that more sumoylated Sp1 was localized in the cytoplasm, and the interaction between SUMO-1-Sp1 and the proteasome subunit rpt6 in HeLa cells was enhanced. In addition, although Sp1 accumulated in the tumorous cervical tissue, it was not prone to sumoylation. Finally, by overexpression of HA (hemagglutinin)-SUMO-1-Sp1-myc, HA-Sp1-myc, and HA-Sp1(K16R), we found that modification of Sp1 by SUMO-1 was important for Sp1 proteolysis. In conclusion, modification of Sp1 by SUMO-1 altered its localization and then increased its interaction with rpt6. This interaction increased the efficiency of Sp1 proteolytic processing and ubiquitination and then resulted in Sp1 degradation. Therefore, sumoylation of Sp1 is attenuated during tumorigenesis in order to increase Sp1 stability.
Institute of Basic Medical Sciences, National Cheng Kung University, Tainan 701, Taiwan.
Yi-Ting
YT
Wang
Jian-Ying
JY
Chuang
Meng-Ru
MR
Shen
Wen-Bin
WB
Yang
Wen-Chang
WC
Chang
Jan-Jong
JJ
Hung
D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000235:genetics / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D005260:Female; D005786:Gene Expression Regulation; D017930:Genes, Reporter; D005982:Glutathione Transferase / Q000378:metabolism; D006367:HeLa Cells; D006388:Hemagglutinins / Q000737:chemistry; D006801:Humans; D006868:Hydrolysis; D007150:Immunohistochemistry; D008156:Luciferases / Q000378:metabolism; D008954:Models, Biological; D009154:Mutation; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D012333:RNA, Messenger / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D025842:SUMO-1 Protein / Q000235:genetics / Q000378:metabolism*; D016329:Sp1 Transcription Factor / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic; D014162:Transfection; D002583:Uterine Cervical Neoplasms / Q000235:genetics / Q000378:metabolism
C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D006388:Hemagglutinins; D012333:RNA, Messenger; D011994:Recombinant Proteins; D025842:SUMO-1 Protein; D016329:Sp1 Transcription Factor; D008156:Luciferases; D005982:Glutathione Transferase; D046988:Proteasome Endopeptidase Complex