|Garcia Iii, Marin|
|Smith, Timothy - Tim|
Submitted to: Endocrinology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/22/2005
Publication Date: 1/3/2006
Citation: Yaden, B.C., Garcia Iii, M., Smith, T.P., Rhodes, S.J. Two Promoters Mediate Transcription from the Human LHX3 gene: Regulation by Nuclear Factor 1 and Specificity Protein 1. Endocrinology 147:324-337. 2006. Interpretive Summary: Comparison of gene sequences between species can identify functional sequences lying along the DNA around the gene, since functionally important sequences are conserved through evolution. In this study, comparison of the bovine gene sequence obtained with the assistance of ARS was used to illuminate functional elements involved in expression of a gene called Lhx3, that encodes a protein critical for development and function of the mammalian pituitary gland. The results indicate that two separate, functional promoters are alternatively used by this gene in humans, producing related but distinct proteins. These results may have consequences in studies of pituitary diseases of humans and livestock, and facilitate investigation of the possibility that DNA sequence variation within cattle might affect pituitary function. Since the pituitary produces hormones with substantial impact on a wide range of biological functions, variation in pituitary function may underlie differences between individual animals in production traits.
Technical Abstract: The LHX3 transcription factor is required for pituitary and nervous system development in mammals. Mutations in the human gene are associated with hormone deficiency diseases. The gene generates two mRNAs, hLHX3a and hLHX3b, which encode three distinct proteins with different properties. Here, the cis elements and trans-acting factors that regulate the basal transcription of the two mRNAs were characterized. A comparative approach was taken featuring analysis of seven mammalian Lhx3 genes, with a focus on the human gene. Two conserved, TATA-less, GC-rich promoters that are employed to transcribe the two mRNAs precede exons 1a and 1b of hLHX3. Transcription start sites were mapped for both promoters. Reporter genes containing ~ 2.0kb of the hLHX3a promoter and ~1.8kb of intron 1a (hLHX3b) are active in pituitary cells. Transfection, site-directed mutation, electrophoretic mobility shift, southwestern blot, and chromatin immunoprecipitation approaches were used to characterize the interaction of transcription factors with conserved elements in the promoters. Sp1 is a potent regulator of both promoters through interaction with GC boxes. In addition, a distal element within intron 1a that is recognized by NFI factors is critical for hLHX3b promoter function. We conclude that dual promoters coordinate regulated production of the two major hLHX3 mRNAs.