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LIM ‐Homeodomain Transcription Factor, L hx2, is involved in Transcriptional Control of Brain‐Specific Promoter/Exon 1f of the Mouse Aromatase Gene
Author(s) -
Honda S.,
Kozako T.,
Shimeno H.,
Soeda S.,
Harada N.
Publication year - 2012
Publication title -
journal of neuroendocrinology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.062
H-Index - 116
eISSN - 1365-2826
pISSN - 0953-8194
DOI - 10.1111/j.1365-2826.2012.02356.x
Subject(s) - biology , chromatin immunoprecipitation , microbiology and biotechnology , transcription factor , promoter , exon , aromatase , transcriptional regulation , electrophoretic mobility shift assay , reporter gene , transcription (linguistics) , gene expression , gene , genetics , cancer , breast cancer , linguistics , philosophy
N eurosteroidal oestrogen has been proposed to play important roles in a variety of reproductive behaviours. A romatase, 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 ( A rom‐Aα), aro‐ AII ( A rom‐ A β) and aro‐ B ( A rom‐ 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 c DNA library. L hx2, 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 L hx2‐binding element. In addition, a chromatin immunoprecipitation assay with an anti‐ L hx2 antibody demonstrated that L hx2 bound to the aro‐ B site in vivo . A reporter assay of the brain‐specific promoter demonstrated increased L hx2‐dependent promoter activity. Furthermore, the time‐dependent increase in aromatase m RNA in primary cultured foetal neurones was suppressed by an small‐interfering RNA ‐mediated knockdown of L hx2 expression. These results show that L hx2 is involved in the transcriptional regulation of aromatase in the rodent brain.