Pdx-1 modulates histone H4 acetylation and insulin gene expression in terminally differentiated alpha-TC-1 cells.
OBJECTIVE
Islet-associated transcription factors play a critical role in regulating pancreatic endocrine cell differentiation and islet hormone gene expression. Both alpha- and beta-cells differentiate from a common endocrine precursor cell. Therefore, it is important to reveal the differential gene expression profiles between alpha- and beta-cells that can direct their terminal cell fates. alpha-TC-1 and beta-TC-1 are 2 terminally differentiated islet tumor cell lines derived from islets transformed by promoter-specific driven SV40 T antigen overexpression. In this study, we demonstrated that Pdx-1 is a potent transcriptional regulator of endogenous insulin gene expression in alpha-TC-1 cells.


METHODS
Reverse transcriptase-polymerase chain reaction and chromatin immunoprecipitation assays were used to analyze gene expression patterns and chromatin modifications in the insulin promoter.


RESULTS
Differential transcription factor expression profiles of alpha-TC-1 and beta-TC-1 cells revealed that INSM-1 and Pdx-1 transcription factors were expressed exclusively in beta-TC-1 cells. Overexpression of Ad-Pdx-1 in alpha-TC-1 cells induced insulin gene expression. Chromatin immunoprecipitation assays in Ad-Pdx-1 alpha-TC-1 cells demonstrated Pdx-1 occupancy and the hyperacetylation of histone H4 in the insulin promoter region.


CONCLUSIONS
Collectively, these experiments revealed that Pdx-1 is a potent transcriptional regulator that is capable of modulating histone H4 acetylation and activates the insulin gene in a terminally differentiated glucagonoma cell line.
Wang
Hong-Wei
HW
The Research Institute for Children, Children's Hospital, 200 Henry Clay Avenue, Research and Education Building, Rm 2211, New Orleans, LA 70118, USA.
Breslin
Mary B
MB
Lan
Michael S
MS
D000107:Acetylation; D000818:Animals; D002454:Cell Differentiation; D045744:Cell Line, Tumor; D015870:Gene Expression / Q000502:physiology; D050416:Glucagon-Secreting Cells / Q000166:cytology / Q000502:physiology*; D006657:Histones / Q000378:metabolism*; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism*; D007328:Insulin / Q000235:genetics*; D050417:Insulin-Secreting Cells / Q000166:cytology / Q000502:physiology*; D051379:Mice; D008822:Mice, Transgenic; D010190:Pancreatic Neoplasms; D016133:Polymerase Chain Reaction; D011401:Promoter Regions, Genetic / Q000502:physiology; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics; D014158:Transcription, Genetic / Q000502:physiology
D006657:Histones; D018398:Homeodomain Proteins; D007328:Insulin; D015534:Trans-Activators; D014157:Transcription Factors; C084010:pancreatic and duodenal homeobox 1 protein