Two promoters mediate transcription from the human LHX3 gene: involvement of nuclear factor I and specificity protein 1.
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 proteins with different properties. Here, the cis elements and trans-acting factors that regulate the basal transcription of the two mRNAs are 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 used to transcribe the mRNAs precede exons 1a and 1b of hLHX3. Transcription start sites were mapped for both promoters. Deletion experiments showed most activity for reporter genes containing the basal promoters in the context of -2.0 kb of hLHX3a and 1.8 kb of intron 1a (hLHX3b). 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. Specificity protein 1 is a regulator of both promoters through interaction with GC boxes. In addition, a distal element within intron 1a that is recognized by nuclear factor I is critical for hLHX3b promoter function. We conclude that dual promoters allow regulated production of two hLHX3 mRNAs.
Yaden
Benjamin C
BC
Department of Biology (B.C.Y., M.G.), Indiana University-Purdue University Indianapolis, Indianapolis, Indiana 46202, USA.
Garcia
Marin
M
Smith
Timothy P L
TP
Rhodes
Simon J
SJ
D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D017124:Conserved Sequence; D018076:DNA, Complementary / Q000235:genetics; D018398:Homeodomain Proteins / Q000235:genetics*; D006801:Humans; D007668:Kidney; D060850:LIM-Homeodomain Proteins; D008322:Mammals; D051379:Mice; D008969:Molecular Sequence Data; D051839:NFI Transcription Factors / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016415:Sequence Alignment; D012689:Sequence Homology, Nucleic Acid; D016329:Sp1 Transcription Factor / Q000378:metabolism*; D014157:Transcription Factors; D014158:Transcription, Genetic
D018076:DNA, Complementary; D018398:Homeodomain Proteins; D060850:LIM-Homeodomain Proteins; C094898:Lhx3 protein; D051839:NFI Transcription Factors; D016329:Sp1 Transcription Factor; D014157:Transcription Factors