LIM-homeodomain transcription factor, Lhx2, is involved in transcriptional control of brain-specific promoter/exon 1f of the mouse aromatase gene.
Neurosteroidal oestrogen has been proposed to play important roles in a variety of reproductive behaviours. Aromatase, a key enzyme in oestrogen synthesis, is localised in neural nuclei of specific brain regions and is developmentally regulated, with a transient expression peak at the perinatal period. The brain-specific promoter of the aromatase gene was analysed aiming to determine the transcriptional control mechanisms that could help explain the spatiotemporal expression. We previously reported that a 202-bp sequence, which is upstream from the transcriptional initiation site, is essential for the basal transcriptional activity. The 202-bp upstream region of brain-specific exon 1 comprises at least three types of cis-acting elements: aro-AI (Arom-Aα), aro-AII (Arom-Aβ) and aro-B (Arom-B). To identify the binding proteins for the cis-acting elements, a yeast one-hybrid screen was performed with these cis-element sequences using a mouse foetal cDNA library. Lhx2, a LIM-homeodomain protein, was identified as one of the aro-B binding proteins. The identification was further confirmed using the gel shift assay, which demonstrated binding competition of nuclear proteins to the aro-B element with a typical Lhx2-binding element. In addition, a chromatin immunoprecipitation assay with an anti-Lhx2 antibody demonstrated that Lhx2 bound to the aro-B site in vivo. A reporter assay of the brain-specific promoter demonstrated increased Lhx2-dependent promoter activity. Furthermore, the time-dependent increase in aromatase mRNA in primary cultured foetal neurones was suppressed by an small-interfering RNA-mediated knockdown of Lhx2 expression. These results show that Lhx2 is involved in the transcriptional regulation of aromatase in the rodent brain.
Department of Biochemistry, Faculty of Pharmaceutical Sciences, Fukuoka University, Fukuoka, Japan. sihonda@fukuoka-u.ac.jp
S
S
Honda
T
T
Kozako
H
H
Shimeno
S
S
Soeda
N
N
Harada
D000818:Animals; D001141:Aromatase / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D001921:Brain / Q000201:enzymology / Q000378:metabolism*; D019556:COS Cells; D002478:Cells, Cultured; D002522:Chlorocebus aethiops; D004622:Embryo, Mammalian; D018507:Gene Expression Regulation, Developmental; D015971:Gene Expression Regulation, Enzymologic / Q000235:genetics; D060850:LIM-Homeodomain Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D051379:Mice; D008813:Mice, Inbred ICR; D018345:Mice, Knockout; D008969:Molecular Sequence Data; D009928:Organ Specificity / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000502:physiology; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism / Q000502:physiology*
D060850:LIM-Homeodomain Proteins; C489784:Lhx2 protein, mouse; D014157:Transcription Factors; D001141:Aromatase