Complex formation and interactions between transcription factors essential for human prolactin receptor gene transcription.

ABSTRACT: The protein association of estrogen receptor ? ER? with DNA-bound SP1 and C/EBP? is essential for the 17?-estradiol (E2)-induced activation of human prolactin receptor (hPRLR) gene transcription. Protein-protein interaction and complex formation at the hPIII promoter of hPRLR was investigated. The basic region and leucine zipper (bZIP) of C/EBP?, zinc finger (ZF) motifs of SP1, and the DNA binding domain of ER? were identified as regions responsible for the interactions between transfactors. The E2-induced interaction was confirmed by bioluminescence resonance energy transfer (BRET) assays of live cells. The combination of BRET/bimolecular luminescence complementation assay revealed that ER? exists as a constitutive homodimer, and E2 induced a change(s) in ER? homodimer conformation favorable for its association with C/EBP? and SP1. Chromatin immunoprecipitation and small interfering RNA knockdown of members of the complex in breast cancer cells demonstrated the endogenous recruitment of components of the complex onto the hPIII promoter of the hPRLR gene. SP1 is the preferred transfactor for the recruitment of ER? to the complex that facilitates the C/EBP? association. The E2/ER?-induced hPRLR transcription was demonstrated in ER?-negative breast cancer cells. This study indicates that the enhanced complex formation of ER? dimer with SP1 and C/EBP? by E2 has an essential role in the transcriptional activation of the hPRLR gene.

SUBMITTER: Kang JH 

PROVIDER: S-EPMC3147787 | biostudies-literature | 2011 Aug

REPOSITORIES: biostudies-literature