Neuron-restricted expression of the rat gonadotropin-releasing hormone gene is conferred by a cell-specific protein complex that binds repeated CAATT elements.
GnRH gene expression is restricted to a tiny population of neurons scattered throughout the mediobasal hypothalamus. The combination of a 300-bp enhancer and the 173-bp promoter from the rat GnRH gene can confer this narrow specificity in transgenic mice and in transfections of hypothalamic GT1-7 cells. In the present study, we identify repeated CAATT elements in the 3' region of the rat GnRH enhancer that bind a tissue-restricted protein complex and play a significant role in cell-restricted expression of the GnRH gene. Deletions of multiple repeats demonstrate their importance in transcriptional activity. In fact, even mutation of a single repeat reduces expression. This reduction can be compensated by the conserved GnRH promoter, which also contains such elements and binds this protein complex. In Southwestern analysis, three proteins from GT1-7 nuclear extract bind to the CAATT element, and these proteins are not found in NIH3T3 cells. This cell-specific protein complex has properties of the Q50 homeodomain family of transcription factors and binds to as many as seven binding sites in the enhancer and promoter to play a key role in GnRH gene expression in the hypothalamus.
Kelley
Carolyn G
CG
Department of Reproductive Medicine, Center for the Study of Reproductive Biology and Disease, University of California, San Diego, La Jolla, California 92093-0674, USA.
Givens
Marjory L
ML
Rave-Harel
Naama
N
Nelson
Shelley B
SB
Anderson
Scott
S
Mellon
Pamela L
PL
D016475:3T3 Cells; D000818:Animals; D022762:CCAAT-Enhancer-Binding Proteins / Q000378:metabolism; D002460:Cell Line; D002467:Cell Nucleus / Q000502:physiology*; D003001:Cloning, Molecular; D004268:DNA-Binding Proteins / Q000378:metabolism*; D007987:Gonadotropin-Releasing Hormone / Q000235:genetics*; D007031:Hypothalamus / Q000502:physiology; D051379:Mice; D008822:Mice, Transgenic; D016297:Mutagenesis, Site-Directed; D009474:Neurons / Q000502:physiology*; D010957:Plasmids; D011401:Promoter Regions, Genetic; D051381:Rats; D011994:Recombinant Proteins / Q000378:metabolism; D013379:Substrate Specificity; D014158:Transcription, Genetic; D014162:Transfection
D022762:CCAAT-Enhancer-Binding Proteins; D004268:DNA-Binding Proteins; D011994:Recombinant Proteins; D007987:Gonadotropin-Releasing Hormone