title: Appearance of the pituitary factor Pit-1 increases chromatin remodeling at hypersensitive site III in the human GH locus.
abstract: Expression of pituitary and placental members of the human GH and chorionic somatomammotropin (CS) gene family is directed by an upstream remote locus control region (LCR). Pituitary-specific expression of GH requires direct binding of Pit-1 (listed as POU1F1 in the HUGO database) to sequences marked by a hypersensitive site (HS) region (HS I/II) 14.6 kb upstream of the GH-N gene (listed as GH1 in the HUGO database). We used human embryonic kidney 293 (HEK293) cells overexpressing wild-type and mutant Pit-1 proteins as a model system to gain insight into the mechanism by which Pit-1 gains access to the GH LCR. Addition of Pit-1 to these cells increased DNA accessibility at HS III, located 28 kb upstream of the human GH-N gene, in a POU homeodomain-dependent manner, as reflected by effects on histone hyperacetylation and RNA polymerase II activity. Direct binding of Pit-1 to HS III sequences is not supported. However, the potential for binding of ETS family members to this region has been demonstrated, and Pit-1 association with this ETS element in HS III sequences requires the POU homeodomain. Also, both ETS1 and ELK1 co-precipitate from human pituitary extracts using two independent sources of Pit-1 antibodies. Finally, overexpression of ELK1 or Pit-1 expression in HEK293 cells increased GH-N RNA levels. However, while ELK1 overexpression also stimulated placental CS RNA levels, the effect of Pit-1 appeared to correlate with ETS factor levels and target GH-N preferentially. These data are consistent with recruitment and an early role for Pit-1 in remodeling of the GH LCR at the constitutively open HS III through protein-protein interaction.
authors.affiliation: Department of Physiology, University of Manitoba, Winnipeg, Manitoba, Canada.
authors.forename: Xiaoyang
authors.initials: X
authors.lastname: Yang
authors.forename: Yan
authors.initials: Y
authors.lastname: Jin
authors.forename: Peter A
authors.initials: PA
authors.lastname: Cattini
mesh_terms: D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D042002:Chromatin Assembly and Disassembly; D005786:Gene Expression Regulation; D019382:Human Growth Hormone / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D019901:Locus Control Region; D008969:Molecular Sequence Data; D010902:Pituitary Gland / Q000378:metabolism; D012313:RNA / Q000235:genetics / Q000378:metabolism; D050817:Transcription Factor Pit-1 / Q000235:genetics / Q000378:metabolism*; D050807:ets-Domain Protein Elk-1 / Q000235:genetics / Q000378:metabolism
chemical_list: D050817:Transcription Factor Pit-1; D050807:ets-Domain Protein Elk-1; D019382:Human Growth Hormone; D012313:RNA
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