TALE homeodomain proteins regulate gonadotropin-releasing hormone gene expression independently and via interactions with Oct-1.
Gonadotropin-releasing hormone (GnRH) is the central regulator of reproductive function. Expression of the GnRH gene is confined to a rare population of neurons scattered throughout the hypothalamus. Restricted expression of the rat GnRH gene is driven by a multicomponent enhancer and an evolutionarily conserved promoter. Oct-1, a ubiquitous POU homeodomain transcription factor, was identified as an essential factor regulating GnRH transcription in the GT1-7 hypothalamic neuronal cell line. In this study, we conducted a two-hybrid interaction screen in yeast using a GT1-7 cDNA library to search for specific Oct-1 cofactors. Using this approach, we isolated Pbx1b, a TALE homeodomain transcription factor that specifically associates with Oct-1. We show that heterodimers containing Pbx/Prep1 or Pbx/Meis1 TALE homeodomain proteins bind to four functional elements within the GnRH regulatory region, each in close proximity to an Oct-1-binding site. Cotransfection experiments indicate that TALE proteins are essential for GnRH promoter activity in the GT1-7 cells. Moreover, Pbx1 and Oct-1, as well as Prep1 and Oct-1, form functional complexes that enhance GnRH gene expression. Finally, Pbx1 is expressed in GnRH neurons in embryonic as well as mature mice, suggesting that the associations between TALE homeodomain proteins and Oct-1 regulate neuron-specific expression of the GnRH gene in vivo.
Rave-Harel
Naama
N
Department of Reproductive Medicine, School of Medicine, University of California, San Diego, La Jolla, California 92903, USA.
Givens
Marjory L
ML
Nelson
Shelley B
SB
Duong
Hao A
HA
Coss
Djurdjica
D
Clark
Melody E
ME
Hall
Sara Barth
SB
Kamps
Mark P
MP
Mellon
Pamela L
PL
D020816:Amino Acid Motifs; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D002478:Cells, Cultured; D002843:Chromatin / Q000378:metabolism; D018076:DNA, Complementary / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D019281:Dimerization; D004305:Dose-Response Relationship, Drug; D015723:Gene Library; D005982:Glutathione Transferase / Q000378:metabolism; D018398:Homeodomain Proteins; D051863:Host Cell Factor C1; D007031:Hypothalamus / Q000378:metabolism; D051379:Mice; D008957:Models, Genetic; D008969:Molecular Sequence Data; D009474:Neurons / Q000378:metabolism; D050811:Octamer Transcription Factor-1; D009841:Oligonucleotides / Q000737:chemistry; D011233:Precipitin Tests; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D051381:Rats; D012097:Repressor Proteins; D014157:Transcription Factors / Q000737:chemistry / Q000378:metabolism*; D014158:Transcription, Genetic; D014162:Transfection; D020798:Two-Hybrid System Techniques
D002843:Chromatin; D018076:DNA, Complementary; D004268:DNA-Binding Proteins; C497693:Hcfc1 protein, mouse; D018398:Homeodomain Proteins; D051863:Host Cell Factor C1; D050811:Octamer Transcription Factor-1; D009841:Oligonucleotides; C494166:Pou2f1 protein, mouse; C494168:Pou2f1 protein, rat; D012097:Repressor Proteins; C490797:Tgif1 protein, mouse; D014157:Transcription Factors; D005982:Glutathione Transferase