RAP1‐like binding activity in islet cells corresponds to members of the Sp1 family of transcription factors

Abstract

Deletion and mutational analyses of the gastrin promoter have identified a binding site for the yeast transcription factor RAP1 relevant for transcriptional activation in islet cells. We here report that the mammalian transcription factors binding to this site in islet cells are the Sp transcription factor members Sp1 and Sp3. Furthermore, functional analyses revealed Sp1‐ and Sp3‐mediated transcriptional activation of gastrin. These data reveal that the zinc finger proteins Sp1 and Sp3 do have similar binding specificities as the multifunctional yeast RAP1 protein.

Characterization of the Mouse Islet-Specific Glucose-6-Phosphatase Catalytic Subunit–Related Protein Gene Promoter by In Situ Footprinting

“…In addition, HNF-3␤ has been implicated in the regulation of pdx-1 (53) and islet GLUT2 (54) gene expression and has also recently been shown to interact with NF-AT to form a calcium response element in the glucagon gene promoter (55). Finally, Sp1 is important in gastrin gene expression (56); gastrin is transiently expressed in fetal pancreatic islet cells, where it may play a role in islet cell neogenesis (57). Detailed studies on the insulin (36,37), glucagon (58), and islet amyloid polypeptide (amylin) (59) promoters suggest that although islet-enriched trans-acting factors do contribute to the expression of these genes, maximal islet-specific expression is conferred by the particular arrangement of trans-acting factors binding these promoters rather than by a single, islet-specific trans-acting factor.…”

Transcriptional study reveals a potential leptin-dependent gene regulatory network in zebrafish brain

“…Another potential scenario could be transcriptional regulation of crhb -coexpression module again by sp3a (identified as potential upstream regulator of the previous module as described above) through binding to rap1 element at upstream sequences of the members of crhb -coexpression module. Again, the overall expression pattern of rap1a is not different between the genotypes, but it is already known that Sp3 and Sp1 can bind to Rap1 binding site in mammals and activate the transcription of Rap1 target genes (Simon et al 1997 ).…”