A single base difference between Pit-1 binding sites at the hGH promoter and locus control region specifies distinct Pit-1 conformations and functions.
Activation of the human growth hormone (hGH-N) gene in pituitary somatotropes is mediated by a locus control region (LCR). This LCR is composed of DNase I-hypersensitive sites (HS) located -14.5 kb to -32 kb relative to the hGH-N promoter. HSI, at -14.5 kb, is the dominant determinant of hGH-N expression and is essential for establishment of a 32-kb domain of histone acetylation that encompasses the active hGH locus. This activity is conferred by three binding sites for the POU domain transcription factor Pit-1. These Pit-1 elements are sufficient to activate hGH-N expression in the mouse pituitary. In contrast, Pit-1 sites at the hGH-N promoter are consistently unable to mediate similar activity. In the present study, we demonstrate that the functional difference between the promoter-proximal and the HSI Pit-1 binding sites can be attributed in part to a single base difference. This base affects the conformation of the Pit-1/DNA complex, and reciprocal exchange of the divergent bases between the two sets of Pit-1 elements results in a partial reversal of their transgenic activities. These data support a model in which the Pit-1 binding sites in the hGH LCR allosterically program the bound Pit-1 complex for chromatin activating functions.
Shewchuk
Brian M
BM
University of Pennsylvania School of Medicine, 415 Curie Blvd., Philadelphia, PA 19103, USA.
Ho
Yugong
Y
Liebhaber
Stephen A
SA
Cooke
Nancy E
NE
D000225:Adenine / Q000378:metabolism; D000818:Animals; D020029:Base Pairing; D001483:Base Sequence; D001665:Binding Sites; D050882:CREB-Binding Protein / Q000378:metabolism; D016384:Consensus Sequence / Q000235:genetics; D015870:Gene Expression; D019382:Human Growth Hormone / Q000235:genetics*; D019901:Locus Control Region / Q000235:genetics*; D051379:Mice; D008822:Mice, Transgenic; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D010447:Peptide Hydrolases / Q000378:metabolism; D010902:Pituitary Gland / Q000166:cytology; D011401:Promoter Regions, Genetic / Q000235:genetics*; D011485:Protein Binding; D011487:Protein Conformation; D051381:Rats; D013941:Thymine / Q000378:metabolism; D050817:Transcription Factor Pit-1 / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*
C494186:Pou1f1 protein, rat; D050817:Transcription Factor Pit-1; D019382:Human Growth Hormone; D050882:CREB-Binding Protein; D010447:Peptide Hydrolases; D000225:Adenine; D013941:Thymine