Pit-1 binding sites at the somatotrope-specific DNase I hypersensitive sites I, II of the human growth hormone locus control region are essential for in vivo hGH-N gene activation.
The human growth hormone gene cluster is composed of five closely related genes. The 5'-most gene in the cluster, hGH-N, is expressed exclusively in somatotropes and lactosomatotropes of the anterior pituitary. Although the hGH-N promoter contains functional binding sites for multiple transcription factors, including Sp1, Zn-15, and Pit-1, predictable and developmentally appropriate expression of hGH-N transgenes in the mouse pituitary requires the presence of a previously characterized locus control region (LCR) composed of multiple chromatin DNase I hypersensitive sites (HS). LCR determinant(s) necessary for hGH-N transgene activation are largely conferred by two closely spaced HS (HS I,II) located 14.5 kilobase pairs upstream of the hGH-N gene. The region sufficient to mediate this activity has recently been sublocalized to a 404-base pair segment of HS I,II (F14 segment). In the present study, we identified multiple binding sites for the pituitary POU domain transcription factor Pit-1 within this segment. Using a transgenic founder assay, these sites were shown to be required for high level, position-independent, and somatotrope-specific expression of a linked hGH-N transgene. Because the Pit-1 sites in the hGH-N gene promoter are insufficient for such gene activation in vivo, these data suggested a unique chromatin-mediated developmental role for Pit-1 in the hGH LCR.
Shewchuk
B M
BM
Department of Genetics, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
Asa
S L
SL
Cooke
N E
NE
Liebhaber
S A
SA
D016475:3T3 Cells; D000818:Animals; D001665:Binding Sites; D002460:Cell Line; D017931:DNA Primers; D015342:DNA Probes; D004268:DNA-Binding Proteins / Q000378:metabolism*; D003850:Deoxyribonuclease I / Q000378:metabolism*; D004622:Embryo, Mammalian; D005314:Embryonic and Fetal Development; D005786:Gene Expression Regulation; D018507:Gene Expression Regulation, Developmental; D019382:Human Growth Hormone / Q000235:genetics*; D006801:Humans; D019901:Locus Control Region; D051379:Mice; D008822:Mice, Transgenic; D005810:Multigene Family; D010911:Pituitary Neoplasms; D011401:Promoter Regions, Genetic; D050817:Transcription Factor Pit-1; D014157:Transcription Factors / Q000378:metabolism*; D015533:Transcriptional Activation; D014407:Tumor Cells, Cultured
D017931:DNA Primers; D015342:DNA Probes; D004268:DNA-Binding Proteins; D003850:Deoxyribonuclease I; D019382:Human Growth Hormone; D050817:Transcription Factor Pit-1; D014157:Transcription Factors; C494187:POU1F1 protein, human; C494185:Pou1f1 protein, mouse