Submitted on March 21, 2006
Accepted on June 7, 2006
Transcription Factor FOXF1 Regulates Growth Hormone Variant Gene Expression
Jefferson Lomenick1*, Michael Hubert2, and Stuart Handwerger2
1 Department of Pediatrics, University of Kentucky, Lexington, Kentucky, United States
2 Department of Pediatrics, Cincinnati Children's Hospital, Cincinnati, Ohio, United States
* To whom correspondence should be addressed. E-mail: jplome2{at}email.uky.edu.
Deletion analysis of the human growth hormone variant (GHV) promoter in transient transfection studies in BeWo choriocarcinoma and HepG2 cells indicated that the region extending from nt -158/+57 retained full transcriptional activity. DNase I footprint analysis of the fragment revealed a protected region at nt -82/-77, which is in a putative FOXF1/FOXF2 binding site. Supershift assays using an antiserum to human FOXF1 demonstrated that the protected region binds FOXF1. Overexpression of FOXF1 in BeWo and HepG2 cells induced the GHV promoter, while overexpression of FOXF2 was without effect. Mutagenesis of the FOXF1/FOXF2 site reduced basal promoter activity by 50-60% and markedly attenuated transactivation of the promoter by FOXF1. These studies indicate that FOXF1 induces GHV expression by interaction with a FOXF1/FOXF2 cis-element in the proximal promoter.
