scholarly journals Binding of activating transcription factor 6 to the A5/Core of the rat insulin II gene promoter does not mediate its transcriptional repression

2011 ◽  
Vol 47 (3) ◽  
pp. 273-283 ◽  
Author(s):  
Julie Amyot ◽  
Isma Benterki ◽  
Ghislaine Fontés ◽  
Derek K Hagman ◽  
Mourad Ferdaoussi ◽  
...  

Pancreatic β-cells have a well-developed endoplasmic reticulum due to their highly specialized secretory function to produce insulin in response to glucose and nutrients. It has been previously reported that overexpression of activating transcription factor 6 (ATF6) reduces insulin gene expression in part via upregulation of small heterodimer partner. In this study, we investigated whether ATF6 directly binds to the insulin gene promoter, and whether its direct binding represses insulin gene promoter activity. A bioinformatics analysis identified a putative ATF6 binding site in the A5/Core region of the rat insulin II gene promoter. Direct binding of ATF6 was confirmed using several approaches. Electrophoretic mobility shift assays in nuclear extracts from MCF7 cells, isolated rat islets and insulin-secreting HIT-T15 cells showed ATF6 binding to the native A5/Core of the rat insulin II gene promoter. Antibody-mediated supershift analyses revealed the presence of both ATF6 isoforms, ATF6α and ATF6β, in the complex. Chromatin immunoprecipitation assays confirmed the binding of ATF6α and ATF6β to a region encompassing the A5/Core of the rat insulin II gene promoter in isolated rat islets. Overexpression of the active (cleaved) fragment of ATF6α, but not ATF6β, inhibited the activity of an insulin promoter–reporter by 50%. However, the inhibitory effect of ATF6α was insensitive to mutational inactivation or deletion of the A5/Core. Therefore, although ATF6 binds directly to the A5/Core of the rat insulin II gene promoter, this direct binding does not appear to contribute to its repressive activity.

2013 ◽  
Vol 8 (2) ◽  
pp. 97-106
Author(s):  
Teodora Daneva ◽  
Shina Pashova ◽  
Radoslava Emilova ◽  
Plamen Padeshki ◽  
Hristo Gagov ◽  
...  

AbstractDownstream regulatory element antagonist modulator (DREAM) protein is a 31 kDa Ca2+-regulated transcriptional repressor. It functions as a silencer of the gene transcription. In low intracellular free Ca2+ concentration DREAM tightly binds to the downstream regulatory element (DRE) of gene promoter and impedes the transcription. In higher Ca2+ concentrations DREAM binds Ca2+ and disconnects from DRE of the gene promoter enabling transcription. We report that DREAM is expressed in different human tissues including the pancreas, where it is located in the islets of Langerhans. Location of DREAM in RIN-F5 cells in cultures is restricted to the nucleus and membranes and changes after increased Ca2+-levels. The proteins dissociate from dimmers to monomers and translocate out of the nucleus. The expression of DREAM in β-cells in the islets of Langerhans regulates the promoter activity of the insulin gene by directly interacting with the sequence located between +52 bp and +81 bp downstream of the transcriptional start site of the promoter. Our results provide evidence for the existence of DRE sequence in the insulin gene promoter. It is suggested that DREAM is a repressor of insulin gene transcription, whose effect is mediated by direct binding to DRE sequence.


1993 ◽  
Vol 197 (2) ◽  
pp. 957-964 ◽  
Author(s):  
E. Yamato ◽  
H. Ikegami ◽  
Y. Tahara ◽  
M. Fukuda ◽  
T. Cha ◽  
...  

Diabetes ◽  
1984 ◽  
Vol 33 (11) ◽  
pp. 1019-1024 ◽  
Author(s):  
G. Gold ◽  
J. Pou ◽  
R. M. Nowlain ◽  
G. M. Grodsky

Diabetes ◽  
1985 ◽  
Vol 34 (6) ◽  
pp. 548-552 ◽  
Author(s):  
R. L. Hanson ◽  
C. M. Isaacson ◽  
L. D. Boyajy

Cryobiology ◽  
1976 ◽  
Vol 13 (6) ◽  
pp. 646-647
Author(s):  
Harvey Bank ◽  
Richard Davis ◽  
James Scoggin ◽  
Richard Weiss ◽  
Dorothy Noe

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