Multiple domains of TonEBP cooperate to stimulate transcription in response to hypertonicity.
Tonicity-responsive enhancer binding protein (TonEBP), also known as NFAT5, belongs to the Rel family of transcriptional activators. In the kidney medulla and thymus, TonEBP plays a major role in protecting renal cells and T cells from the deleterious effects of ambient hypertonicity. TonEBP is stimulated by hypertonicity via several pathways: increased expression of protein, nuclear translocation, and increased transactivation. In this study, we identified five domains of TonEBP involved in transactivation. The two conserved glutamine repeats were not involved in transactivation. There were three activation domains that could stimulate transcription independently. In addition, there were two modulation domains that potentiated the activity of the activation domains. One of the activation domains is unique to a splice isoform that is more active than others, indicating that alternative splicing can affect the activity of TonEBP. Another activation domain and one of the modulation domains were stimulated by hypertonicity. All the five domains acted in synergy in every combination. Although overall phosphorylation of TonEBP increased in response to hypertonicity, phosphorylation of the activation and modulation domains did not increase in isolation. In sum, TonEBP possesses far more elaborate domains involved in transactivation compared with other Rel proteins.
Lee
Sang Do
SD
Department of Medicine, University of Maryland, Baltimore, Maryland 21201, USA.
Colla
Emanuela
E
Sheen
Mee Rie
MR
Na
Ki Young
KY
Kwon
H Moo
HM
D021581:Active Transport, Cell Nucleus; D000818:Animals; D019556:COS Cells; D005822:Genetic Vectors; D005973:Glutamine / Q000737:chemistry; D015151:Immunoblotting; D007668:Kidney / Q000378:metabolism; D008156:Luciferases / Q000378:metabolism; D008957:Models, Genetic; D010766:Phosphorylation; D020033:Protein Isoforms; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013601:T-Lymphocytes / Q000378:metabolism; D013950:Thymus Gland / Q000378:metabolism; D015534:Trans-Activators / Q000737:chemistry*; D014157:Transcription Factors; D014158:Transcription, Genetic; D015533:Transcriptional Activation
C118125:NFAT5 protein, human; D020033:Protein Isoforms; D011993:Recombinant Fusion Proteins; D015534:Trans-Activators; D014157:Transcription Factors; D005973:Glutamine; D008156:Luciferases