Identification of an INSM1-binding site in the insulin promoter: negative regulation of the insulin gene transcription.
In this study, an insulinoma-associated antigen-1 (INSM1)-binding site in the proximal promoter sequence of the insulin gene was identified. The co-transfection of INSM1 with rat insulin I/II promoter-driven reporter genes exhibited a 40-50% inhibitory effect on the reporter activity. Mutational experiments were performed by introducing a substitution, GG to AT, into the INSM1 core binding site of the rat insulin I/II promoters. The mutated insulin promoter exhibited a three- to 20-fold increase in the promoter activity over the wild-type promoter in several insulinoma cell lines. Moreover, INSM1 overexpression exhibited no inhibitory effect on the mutated insulin promoter. Chromatin immunoprecipitation assays using beta TC-1, mouse fetal pancreas, and Ad-INSM1-transduced human islets demonstrated that INSM1 occupies the endogenous insulin promoter sequence containing the INSM1-binding site in vivo. The binding of the INSM1 to the insulin promoter could suppress approximately 50% of insulin message in human islets. The mechanism for transcriptional repression of the insulin gene by INSM1 is mediated through the recruitment of cyclin D1 and histone deacetylase-3 to the insulin promoter. Anti-INSM1 or anti-cyclin D1 morpholino treatment of fetal mouse pancreas enhances the insulin promoter activity. These data strongly support the view that INSM1 is a new zinc-finger transcription factor that modulates insulin gene transcription during early pancreas development.
Wang
Hong-Wei
HW
The Research Institute for Children, Children's Hospital, 200 Henry Clay Avenue, New Orleans, Louisiana 70118, USA.
Muguira
Michelle
M
Liu
Wei-Dong
WD
Zhang
Tao
T
Chen
Chiachen
C
Aucoin
Rebecca
R
Breslin
Mary B
MB
Lan
Michael S
MS
D000818:Animals; D001665:Binding Sites; D045744:Cell Line, Tumor; D019938:Cyclin D1 / Q000502:physiology; D004268:DNA-Binding Proteins / Q000502:physiology*; D005786:Gene Expression Regulation; D006655:Histone Deacetylases / Q000502:physiology; D006801:Humans; D007328:Insulin / Q000235:genetics*; D051379:Mice; D010179:Pancreas / Q000196:embryology; D011401:Promoter Regions, Genetic; D051381:Rats; D012097:Repressor Proteins / Q000502:physiology*; D014158:Transcription, Genetic; D000099186:Histone Deacetylase 3
D019938:Cyclin D1; D004268:DNA-Binding Proteins; D006655:Histone Deacetylases; D007328:Insulin; D012097:Repressor Proteins; D000099186:Histone Deacetylase 3; C530104:CCND1 protein, human; C087342:INSM1 protein, human