Involvement of mPOU (Brn-5), a class VI POU protein, in the gene expression of Pit-1 as well as PRL

Mol Cell Endocrinol. 2008 Jan 2;280(1-2):20-9. doi: 10.1016/j.mce.2007.09.002. Epub 2007 Sep 8.

Abstract

PRL is mainly expressed in the pituitary and its gene expression is regulated by a variety of transcription factors including Pit-1. Brn-5 is a transcription factor that binds to Pit-1 binding elements and stimulates PRL reporter gene expression. In this study, the role of Brn-5 was examined. RNA interference (RNAi) against Brn-5 leaded to reduction in PRL content of GH3 cells, indicating endogenous Brn-5 may play a role in PRL gene expression. Furthermore Brn-5 RNAi decreased Pit-1 mRNA. Transfection of expression vectors for mPOU (human ortholog of Brn-5) modestly but significantly stimulated activities of PRL-Luc and Pit-1-Luc reporter genes in GH3 and HEK 293 cells. In addition, mPOU showed synergistic action with Pit-1 and CBP on PRL-Luc expression. mPOU-FL, a splicing variant of mPOU, showed weaker activity than mPOU. Chip assay suggested binding of mPOU to PRL and Pit-1 promoters of genomic DNA. Taken together, these results suggest that mPOU (Brn-5) enhances PRL gene expression directly in association with Pit-1 and CBP, and indirectly via the activation of Pit-1 gene expression.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alternative Splicing
  • Animals
  • CREB-Binding Protein / metabolism
  • Cell Line
  • Gene Expression Regulation*
  • Genes, Reporter
  • Humans
  • Lactotrophs / metabolism*
  • POU Domain Factors / genetics
  • POU Domain Factors / metabolism*
  • Pituitary Gland / cytology
  • Pituitary Gland / metabolism*
  • Prolactin / genetics
  • Prolactin / metabolism*
  • Promoter Regions, Genetic
  • RNA Interference
  • RNA, Messenger / metabolism
  • RNA, Small Interfering / metabolism
  • Rats
  • Transcription Factor Pit-1 / genetics
  • Transcription Factor Pit-1 / metabolism*
  • Transfection

Substances

  • POU Domain Factors
  • Pou1f1 protein, rat
  • Pou6f1 protein, rat
  • RNA, Messenger
  • RNA, Small Interfering
  • Transcription Factor Pit-1
  • Prolactin
  • CREB-Binding Protein