Identification of novel regulatory NFAT and TFII-I binding elements in the calbindin-D28k promoter in response to serum deprivation

• Published in: Biochemical and biophysical research communications 2015-09, Vol.465 (3), p.414-420
• Main Authors: Hajibeigi, Asghar, Dioum, Elhadji M., Guo, Jianfei, Öz, Orhan K.
• Format: Article
• Language: English
• Subjects: Animals; Apoptosis; Base Sequence; Binding Sites; bioinformatics; blood serum; calbindin; Calbindin 1 - genetics; Calbindin-D28k; calcium; Calcium binding proteins; charcoal; chromatin; culture media; Culture Media, Serum-Free; Dogs; HEK293 Cells; HeLa Cells; homeostasis; Humans; ischemia; kidneys; Madin Darby Canine Kidney Cells; mice; Molecular Sequence Data; NFAT transcription factors; NFATC Transcription Factors - genetics; precipitin tests; promoter regions; Promoter Regions, Genetic; Protein Binding; Regulatory Elements, Transcriptional - genetics; Serum deprivation; TFII-I; tissues; transactivators; transcription (genetics); Transcription Factors, TFII - genetics
• ISSN: 0006-291X; 1090-2104
• DOI: 10.1016/j.bbrc.2015.08.024

Calbindin-D28k, a key regulator of calcium homeostasis plays a cytoprotective role in various tissues. We used serum free (SFM) and charcoal stripped serum (csFBS) culture media as models of cellular stress to modulate calbindin D28k expression and identify regulatory cis-elements and trans-acting factors in kidney and beta cells. The murine calbindin-D28k promoter activity was significantly upregulated under SFM or csFBS condition. Promoter analysis revealed evolutionary conserved regulatory cis-elements and deletion of 23 nt from +117/+139 as critical for basal transcription. Bioinformatics analysis of the promoter revealed conserved NFAT and TFII regulators elements. Forced expression of NFAT stimulated promoter activity. Inhibition of NFAT transcriptional activity by FK506 attenuated calbindin-D28k expression. TFII-I was shown to be necessary for basal promoter activity and to act cooperatively with NFAT. Using chromatin immunoprecipitation (ChIP) assays, NFAT was shown to bind to both proximal and distal promoter regions. ChIP assays also revealed recruitment of TFII to the −36/+139 region. Knockdown of TFII-I decreased promoter activity. In summary, calbindin-D28k expression during serum deprivation is partly regulated by NFAT and TF-II. This regulation may be important in vivo during ischemia and growth factor withdrawal to regulate cellular function and maintenance. •Calbindin-D28k (D28k) promoter activity in kidney and pancreatic beta cells increases in response to serum withdrawal.•Cis-elements downstream within +2/+139 are necessary for full promoter activity.•A 23nt sequence, +117/+139, is critical for basal transcription.•NFAT and TFII-I binding sites in the proximal promoter contribute to transcriptional control of D28k expression.•Discovery of a novel regulatory mechanism of D28k expression by CN/NFAT may lead to new methods to modulate cell survival.