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Prolactin induction of insulin gene transcription: roles of glucose and signal transducer and activator of transcription 5.

Publication ,  Journal Article
Fleenor, DE; Freemark, M
Published in: Endocrinology
July 2001

GH and PRL stimulate insulin production in pancreatic beta-cells through induction of insulin gene transcription. The transcriptional effects of GH are mediated through the binding of signal transducer and activator of transcription-5 (STAT5) to a consensus recognition sequence (TTCnnnGAA) in the rat insulin-1 promoter. In this study we demonstrate that PRL also induces the binding of STAT5 proteins to the rat insulin-1 STAT5 motif. However, the magnitude of binding of STAT5 nuclear proteins, as assessed by electrophoretic mobility shift assays, was only 1/30th that of the binding of the same STAT5 proteins to the beta-casein STAT5 site. The differences in the affinities of the rat insulin-1 and beta-casein STAT5 motifs are explained in part by differences in promoter sequences flanking the STAT5 sites. To assess the importance of the STAT motif in PRL induction of insulin gene transcription, we deleted the STAT5 consensus sequence in the rat insulin 1 promoter, cloned the truncated promoter upstream of the luciferase reporter gene, and transfected the construct into rat insulinoma (INS-1) cells. The transcriptional activity of this construct was compared with that of the wild-type promoter. Although deletion of the STAT5 site in the promoter reduced the basal luciferase activity, the response to PRL was unaffected. PRL also induced transcription of constructs containing the wild-type human insulin promoter or the rat insulin-2 promoter, which contain no classic STAT5 sequences. The transcriptional effect of PRL was manifest even when cells were incubated in glucose-free medium, indicating that the action of the hormone is not mediated solely through changes in glucose uptake or glucose metabolism. To identify PRL-responsive regions of the rat and human insulin promoters, we constructed a series of promoter truncations and assessed their responsiveness to PRL. A PRL-responsive region of the rat insulin-1 promoter was localized between nucleotides -165 and -109. A PRL-responsive region of the human insulin promoter was localized between nucleotides -346 and -250. Additional regions of the human and rat insulin-1 promoters were required for PRL induction of a heterologous, minimal thymidine kinase promoter, suggesting that there are multiple PRL-responsive elements in the insulin genes. These observations suggest a glucose- and STAT5-independent pathway by which PRL may induce insulin gene transcription.

Duke Scholars

Published In

Endocrinology

DOI

ISSN

0013-7227

Publication Date

July 2001

Volume

142

Issue

7

Start / End Page

2805 / 2810

Location

United States

Related Subject Headings

  • Tumor Cells, Cultured
  • Transcription, Genetic
  • Trans-Activators
  • Thymidine Kinase
  • STAT5 Transcription Factor
  • Rats
  • Protein Isoforms
  • Promoter Regions, Genetic
  • Prolactin
  • Milk Proteins
 

Citation

APA
Chicago
ICMJE
MLA
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Fleenor, D. E., & Freemark, M. (2001). Prolactin induction of insulin gene transcription: roles of glucose and signal transducer and activator of transcription 5. Endocrinology, 142(7), 2805–2810. https://doi.org/10.1210/endo.142.7.8267
Fleenor, D. E., and M. Freemark. “Prolactin induction of insulin gene transcription: roles of glucose and signal transducer and activator of transcription 5.Endocrinology 142, no. 7 (July 2001): 2805–10. https://doi.org/10.1210/endo.142.7.8267.
Fleenor, D. E., and M. Freemark. “Prolactin induction of insulin gene transcription: roles of glucose and signal transducer and activator of transcription 5.Endocrinology, vol. 142, no. 7, July 2001, pp. 2805–10. Pubmed, doi:10.1210/endo.142.7.8267.
Journal cover image

Published In

Endocrinology

DOI

ISSN

0013-7227

Publication Date

July 2001

Volume

142

Issue

7

Start / End Page

2805 / 2810

Location

United States

Related Subject Headings

  • Tumor Cells, Cultured
  • Transcription, Genetic
  • Trans-Activators
  • Thymidine Kinase
  • STAT5 Transcription Factor
  • Rats
  • Protein Isoforms
  • Promoter Regions, Genetic
  • Prolactin
  • Milk Proteins